icse syllabus for class 9 geography

ICSE Solutions for Class 9 Geography – Natural Regions of the World

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
Define the term ‘natural region’.
Answer:
A natural region refers to a part of Earth’s surface having a particular uniformity in physical and climatic elements.

Question 2.
Name any four natural regions of the world.
Answer:
Equatorial Region, Tropical Grasslands (Savanah), Tropical Monsoon type and Tropical Deserts.

Question 3.
Briefly state the importance of climate.
Answer:
Climate imparts an important effect on human life, as the life style, occupations, trade facilities all are deeply related to the climatic behaviour of a particular natural region. Climate has a remarkable impact on human efficiency too.

Question 4.
State the location of the Equatorial Region.
Answer:
It is found in Amazon basic, Congo basin and Indonesia etc.

Question 5.
What is the latitudinal extent of the Monsoon climate?
Answer:
Latitudinal extent is from 8°N – 23 1/2° N and 8°S – 23 1/2° S.

Question 6.
Name the two dominant type of vegetation of the Equatorial region.
Answer:
Rubber and ebony.

Question 7.
State the location of the Tropical Desert Climate type.
Answer:
These are located in the western margins of the continents between 15° to 30° North and South Latitudes, where the trade winds blow from land towards sea keeping these areas almost rain less.

Question 8.
What are xerophytic plants ?
Answer:
These plants are leafless to check transpiration and store water in their stems.

Question 9.
What local conditions produce variation in the Mediterranean Type of climate ?
Answer:
It is known for summer drought and winter rain. On account of being located in the zone of Westerlies, the rainfall decreases from coastal parts towards the interior parts. This region is also affected by cold polar winds known as ‘Mistral’ in Rhone valley of France and ‘Bora’ in Greece. Some hot and dry winds also affect North Africa called as ‘Sirrco’ and ‘Khamsin’ in Egypt. These winds increase the temperature and cause damage to crops.

Question 10.
State the rainfall pattern in the Mediterranean climate.
Answer:
Rainfall occurs mostly in winter season. Annual average is from 35 cm to 75 cm. Which is more in the pole ward sides of the region moderate rainfall makes the weather pleasant with sufficient sunny days attract tourists in great numbers to the region.

Question 11.
What type of vegetation is found in the Mediterranean region ?
Answer:
It is deciduous type with great efficiency to withstand long summer drought. Mostly citrus fruits are grown. This region is the most remarkable producer of citrus fruits. Dominant trees are oak, laurel, cork, oleander, beech, ash, olive etc.

Question 12.
Name six Temperate Grasslands of the world.
Answer:
These names are Prairies (N.America), Pampas (S. America), Velds (S. Africa), Downs (Australia), Steppes (Russia) and Pustaz (Europe).

Question 13.
Why there are no trees in the Steppe type climate region?
Answer:
The rainfall is very less nearly 20 cm. It is not sufficient for the growth of the trees and there are extensive soft grasslands.

Question 14.
What is the temperature range in winter of the Cool Continental Climate Type ?
Answer:
Temperature almost remains below freezing point and the temperature range may be more than 50°C, i.e. It may be 1 – 2° C and – 50° C in severe winters.

Question 15.
Name the areas of the Cool Temperate Ocean type climate
Answer:
Great Britain, N. Spain, France, Belgium, N. Germany, Denmark, Western Canada (British Columbia), Washington, Oregon (U.S.A.), Chile (S.America), Falkland islands, Tasmania, New Zealand etc.

Question 16.
Give the annual rainfall of the above tropical region.
Answer:
Rainfall varies from 50 cm to 120 cm.

II. Give reasons for each of the following 

Question 1.
There is a uniformly high temperature in the Equatorial region.
Answer:
Due to regular vertical rays of the sun the temperature always remains high. This region always comes directly on the front of the sun.

Question 2.
Deciduous trees shed their leaves in the dry season.
Answer:
Deciduous trees shed their leaves in the dry season to preserve the moisture which could be lost by transpiration through the leaves. After the slight winter rainfall the trees again sprout with new leaves.

Question 3.
In the Tropical Desert climate region, Trade Winds are dry.
Answer:
In the Tropical Hot Desert region, the Trade Winds blow from land towards the sea, so these cannot gain moisture and are dry and there is no rainfall and a prolonged dry and hot season.

Question 4.
In the Mediterranean region of Europe, winds blow deep inside the land.
Answer:
This region falls in the belt of Westerlies, which blow with a great force from S.W. to N.E. and enter deep into the land region. Due to coming in contact with the Cold Polar Frost these are accompanied by temperate cyclones with great speed covering long distance from west to east from the Mediterranean sea upto China crossing the whole mid-Asia continent.

Question 5.
Tropical grasslands have great potential for the cultivation of crops like cotton and coffee.
Answer:
Due to ideal temperature of 25° C to 30° C and quite hot summer season and ample rainfall average about 100 cm, present suitable condition for plantation crops like cotton and coffee.

Question 6.
The Taiga region is sparsely populated.
Answer:
The Taiga region is covered with extensive belt of evergreen coniferous trees with lumbering and fur industry as main occupations. So, these forests are kept safe and no deforestation is done for any agricultural occupation and human settlements, so is less populated.

Question 7.
There are no trees in the Tundra Region.
Answer:
The Tundra region is covered with perpetual snow and the temperature away below freezing point does not allow the : growth of trees. Only moss and small flowery plants and lichen etc grow in short summer season only with 10°C temperature at the most. Inspite of the six months’ sunlight, the snow cover reflects the insolation.

Question 8.
Patagonia is a desert in the rain shadow of the Andes.
Answer:
Patagonia is a cold desert in South America due to being in the rain shadow area of the Andes and does not get rainfall and is a cold and dry desert with its major part in Argentina.

III. Long Answer Questions

Question 1.
Describe the general characteristics of natural regions. “Name four major natural regions in the world.
Answer:
Every natural region has a combination of particular climate and physical elements different from other. On this basis the classification of the natural regions is done for the facility to adopt it by human beings adjusting the natural impact with human occupations.
Four natural regions :
Equatorial Region, Tropical Grasslands (Savanah), Tropical Monsoon type and Tropical Deserts.

Question 2.
State the factors of responsible for climatic classification of natural regions
Answer:
The amount of insolation decreases as the latitude increases. So there is difference in different seasons in differing latitudes, e.g., the equatorial region remains hot and wet throughout the year, the tropical monsoon land experiences particular summer, rainy, autumn winter and spring seasons. The tropical deserts are almost dry and hot. The temperate grasslands are noted for short summer and long winters.
The Mediterranean region is noted for warm summer and rainy winter. Taiga region has a long cold winter and very short summer. Tundra region is known for perpetual snow due to freezing temperature all the year. Due to the tilted axis of the earth. North and South Polar region experience six months day and six months night respectively with continuous lowest temperature below – 58°C.

Question 3.
Give a brief account of Rainforests together with their location and types of trees.
Answer:
Tropical rain forest are found in equatorial region due to excessive rainfall and temperature. These are known as ‘Selvas’ in Amazon basin. Other regions are Zaire basin, Indonesia, Malaysia and S. Philippines. Main types of trees are ebony, mahogany, cinchona, rosewood, rubber etc.

Question 4.
Discuss the vegetation of the Tropical Monsoon type climate.
Answer:
Due to particular rainy season followed by autumn and winter, this type of climate has deciduous vegetation. The coastal parts have tropical evergreen Rain Forests slightly different from equatorial vegetation, these are rosewood, ebony, sisam, baniboo etc. with much height upto 60 meters. Deciduous tree are found in khair, Tendu etc.

Question 5.
Bring out the chief characteristics of the Mediterranean type climate.
Answer:
This climate is remarkable for rainy winters and long dry summers with moderate rainfall upto 75 cm, pleasant climate, sunny days. This climate is suitable for photography and film industry e.g. Hollywood in Los Angles (California) of U.S.A.

Question 6.
Differentiate between Mediterranean type climate and China type climate.
Answer:
Mediterranean climate :

(a) It is found in the western margins of Continents
(b) It is known as subtropical winter Rain zone with a long drought season.
(c) Average rainfall is 35 cm to 75 cm
(d) It is good for citrus fruits.

China type climate :

(a) It is found in the eastern margins of the continents.
(b) It has got ample rainfall with a short drought season.
(c) Average rainfall is 110 cm.
(d) It is suitable for various crops.

Question 7.
Bring out the differences between the tropical and temperate deserts in terms of climate and vegetation.
Answer:
Tropical Deserts :

(a) These are located between 15° to 30°North and South latitudes.
(b) Climate is hot and dry.
(c) Trees are palm trees, cactus, xerophytic plants.
(d) Temperature may range from 30°C to 45°C annual rainfall less than 25 cm, winter temperature below 20°C. It is known as the highest range of temperature.

Temperate Deserts :

(a) These are found between 40° to 55° North and South latitudes.
(b) Climate is cold and dry.
(c) Thorny bushes, long rooted grass, small trees etc.
(d) Temperature is between 3°C and 12°C, annual rainfall is 20cm to 60 cm. In Calgary region of Canada temperature is -10°C, Range of temperature is moderate.

Question 8.
Prepare the rainfall graph of the data given below and answer the questions that follow :

(a) What is the average annual temperature ?
(b) Calculate the annual range of temperature.
(c) In which climate type is this station ?

Answer:

(a) Average annual temperature is 27.2°C. (26.9 + 27.6 + 28.7 + 29.1 + 28.4 + 26.5 + 25.9 + 26.0 + 26.4 + 26.8 + 27.1 + 26.9) ÷ 12 = 326.3 ÷ 12 = 27.2
(b) Range of temperature is 3.2° C. 29.1 – 25.9 = 3.2
(c) The climatic type is equatorial climate.

Practice Questions (Solved)

Question 1.
What do you understand by a ‘natural resource’ ?
Answer:
The things that we and other living organisms (plants and animals) required for living and provided as natural gifts are called natural resources.

Question 2.
How many kinds of natural resources are available ? Name them.
Answer:
There are two types of natural resources i.e. Renewable resources and Non-renewable resources. These are air, water, plants, sunlight which are renewable, some are soil, minerals which are Non-renewable in case of reckless exploitation.

Question 3.
What are the various uses of wood ?
Answer:
The wood is one of the most important resource, as it provides timber for houses, construction, fuel for household and industrial purposes, transport lines, agricultural implements, furniture, sports goods, stationery and various consumer goods.

Question 4.
Why are coal and petroleum called fossil fuels ?
Answer:
The coal is formed by compression of carboniferous age forests between impervious sedimentary rock-folds and the petroleum is the stored ‘body oil of dinosaurs of Jurassic period in between the impervious rocks within the poses of shale rocks. So these are called the fossil fuels on account of being buried within the rocks like the fossils for a long period under the pressure of tectonic forces.

Question 5.
What are the benefits of non-conventional sources of energy?
Answer:
Non-conventional sources of energy are solar, geothermal, tidal energies. These are perennial sources i.e. non-exhaustible or renewable resources which can be obtained for ever and are also pollution-free. Although the establishment and apparatus of these sources is quite costly, but their returns are life – long.

Question 6.
What is the difference between sea water and fresh water?
Answer:
Sea water is saline in which the percentage of salinity is 3.5% i.e. 35 (35 per thousand) but the fresh water is not saline and can be used for drinking, household and industrial purposes.

Question 7.
What is the total percentage of fresh water on the earth?
Answer:
Out of 100% Water bodies on the earth 97% is occupied by the oceans, and only 3% is comprised by fresh water, again out of this 2% is occupied by snow lands and only 1 % is taken by fresh water bodies e.g. ponds, lakes, rivers etc.

Question 8.
What is hydro logical cycle ?
Answer:
The water of ocean is evaporated in large amount into the atmosphere and then condensed into the clouds, fog, mist etc. After the dew point arises, precipitation takes place and fill up the fresh water bodies of the land surface. Again the water flow goes into the ocean and in this way a complete hydro logical cycle works on the earth. This is beneficial for the life on the earth, as fresh water is provided for agriculture and other occupations.

Question 9.
What gases does air contain ?
Answer:
Air mainly contains oxygen and nitrogen. Carbon dioxide and argon are also found in air.

Question 10.
Name the gases that are found in air along with their percentage.
Answer:
Oxygen 21 %, Nitrogen 78%, Argon 0.9%, others 0.1 %

Question 11.
Why is oxygen essential ?
Answer:
Oxygen is essential as it supports respiration making life possible on the earth.

Question 12.
How is carbon dioxide useful ?
Answer:
Carbon dioxide in the air is used by plants to produce food and oxygen.

Question 13.
How does an air conditioner help ?
Answer:
An air conditioner keeps the temperature and moisture of the air in a room at comfortable levels (usually between 20° and 25° C and a relative humidity of 35 – 70%).

Question 14.
name five resources which we get from the earth.
Answer:
Soil, minerals, coal, petroleum and plants.

Question 15.
What does subsoil contain ?
Answer:
Humus, rocks and minerals.

Question 16.
What are minerals ? List any four minerals.
Answer:
Minerals are inorganic substances obtained from Earth through the process of mining. Coal, manganese, iron ore and gold.

Question 17.
What type of resources are minerals ?
Answer:
Minerals are non-renewable natural resources which means that once mined, their deposits are depleted and lost forever without any chance of replenishment.

Question 18.
How do forests retain water ?
Answer:
Forests absorb rainwater and only gradually release it into rivers.

Question 19.
What is meant by deforestation ?
Answer:
Deforestation means cutting down and clearing of tree covers from forest areas to get land for agricultural use, cattle grazing . or exporting timber.

Question 20.
What happens when fossil fuels are burnt ?
Answer:
When fossil fuels are burnt they cause air pollution. Greenhouse gases are formed and acid rain may also fall.

Question 21.
List the inexhaustible sources of energy.
Answer:
Solar, hydel, tidal, wind and nuclear energy.

Question 22.
Which places in India can be used for tidal power generation ?
Answer:
Gulf of Cambay, Gulf of Kutch, Sunderbans and other coastal areas.

Question 23.
How many biogas plants have been set up in India under the National Biogas Development Programme ?
Answer:
15 lakh biogas plants.

Question 24.
What is geothermal energy ? Give examples of geothermal energy.
Answer:
It is the conversion of natural heat from the interior of the Earth to heat buildings and generate electricity. Volcanoes and natural springs.

Question 25.
How is ground water formed ?
Answer:
Water falls on earth in form of rain. The water from rainfall which reaches land percolates into the soil to reach deep down. Then it becomes a part of ground water.

Question 26.
List the advantages and disadvantages of solar energy.
Answer:
Solar energy can be gained by using a solar cell, a device that produces electricity directly from sunlight. By using special mirrors that focus the sunlight from a large area to a small area, solar-energy can be utilized for boiling water or for creating steam for producing electricity. The same collected solar energy can be localized into a solar furnace to heat oil. This process is used to boil water that drives turbines which produce electricity. Solar energy can be utilized to get drinking water from salty water sources. Salty water can be boiled and collected in form of steam. Salt, left behind is removed, and the steam gets cooler to turn back into water. Solar energy is used in desalination plant for this purpose. Photovoltaic cells have been used to electrify remote villages in rural Rajasthan, Uttar Pradesh, Gujarat and Haryana.
Solar energy has some disadvantages also, like the availability of sunlight only in daytime, lack of efficiency on a cloudy or rainy day, and feasibility only in countries located in regions which receive direct rays of the sun for a number of months in a year.

Question 27.
What is hydrological cycle ?
Answer:
Radiation from the sun causes water to evaporate from the water bodies in the form of water vapour. From plants, water continues to evaporate into air. This is done through the process of transpiration. Some water vapour is also retained by air. When the water vapour in the air rises up it combines to form clouds. In the clouds, there is moisture, i.e. water, which may fall on earth in form of rain, hail or snow. Some rain water that falls to the ground gets absorbed by the soil to form underground water.
The remaining water reaches the water bodies (river, ponds, lakes and oceans). This is the hydrological or water cycle that continues in nature all the time.

Question 28.
What is the aim of dividing the world into natural regions?
Answer:
The aim of dividing the world into natural regions is to study the variations in natural environment and its impact on human life in different parts of the world.

Question 29.
What forms the basis of a general scheme of natural regions of the world ?
Answer:
The latitudinal location and extent of an area forms the basis of a general scheme of natural regions.

Question 30.
Mention the regions that cover the following :

(a) Tropical Regions
(b) Warm Temperate Regions
(c) Cool Temperate Regions
(d) Polar Regions.

Answer:
(a) Tropical regions cover :

1. Equatorial region
2. Tropical grassland (savanna)
3. Tropical desert
4. Tropical east margin.

(b) Warm temperate regions cover :

1. Mediterranean region
2. China type
3. Continental interior

(c) Cool temperate regions cover :

1. Cool temperate west margin
2. Temperate grasslands
3. Cool temperate east margin
4. Cool temperate (Taiga)

(d) Polar regions :

1. Tundra (Cold desert)
2. Ice caps

Question 31.
Where does the tropical region lie ?
Answer:
Tropical region lies roughly between 30°N and 30°S latitudes.

Question 32.
Where does the warm temperate region lie ?
Answer:
The warm temperate region lies between 30°North and South and 45° North and South of the Equator.

Question 33.
Where does the cool temperate region lie ?
Answer:
The cool temperate region lies roughly between 45° North and 65° North as well as between 45° South and 65° South latitudes.

Question 34.
Where does the polar region lie ?
Answer:
Polar region lies beyond 65° latitude (i.e., beyond Arctic and the Antarctic circles) and the Pole in each hemisphere.

Question 35.
Name the continents where the equatorial regions are situated.
Answer:
The continents where the equatorial regions are situated are – South America, Africa and Asia.

Question 36.
Which parts of Asia and S. America included in equatorial forest region.
Answer:
Equatorial region in Asia includes :

• Indonesia
• Malaysia
• Irian Jaya
• Papua New Guinea and
• The southern islands of Philippines

Equatorial region in South America includes :

• The Amazon basin
• The coastal lowlands between the Guyana and Brazilian highlands.
• The coastal part of Columbia.

Question 37.
Name the areas constituting the equatorial region in Africa.
Answer:
The areas constituting the equatorial region in Africa are :

1. The Congo basin
2. The coast of Guinea
3. Southern parts of Nigeria and Ghana.

Question 38.
What are the chief features of the climate of equatorial regions ?
Answer:
Chief features of climate of equatorial region are :

1. It receives a large amount of insolation.
2. Relative humidity remains high throughout the year.
3. Almost equal days and nights throughout the year.
4. Little seasonal variation in the climatic conditions because of vertical sun rays all the year round.
5. Climate is not unbearable because of cloudiness and heavy rainfall.

Question 39.
Mention the major trees found in equatorial forests.
Answer:
Major trees of equatorial forests are :
Mahogany, Ebony, Ivory wood, Dye wood, Cinchona and Rose wood.

Question 40.
Name any four countries which have monsoon climate.
Answer:
India, Pakistan, Bangladesh, Myanmar, etc. have monsoon climate.

Question 41.
Mention the location of Tropical monsoon type regions.
Answer:
Monsoon type regions are located in the zone extending between 5° and 30° latitudes on either side of the Equator.

Question 42.
What is the range of temperature in monsoon region in the interior of the continent.
Answer:
Summer temperature varies from 35°C to 38°C in the interior. Winter temperature varies from 15°C to 18°C in the interior.

Question 43.
Why is there complete reversal of pressure gradients over Asiatic landmass ?
Answer:
There is complete reversal of pressure gradients over Asiatic landmass because of north wards and southwards migration of the Sun and consequent differential heating of the continent and adjoining areas.

Question 44.
Name any two states of India which receive winter rainfall.
Answer:
The eastern coast of Tamil Nadu and Andhra Pradesh receives much rainfall during winter season through north-east monsoons.

Question 45.
What is the location of tropical desert ?
Answer:
Tropical deserts are located on the western coasts of the continents between the latitudes of 15° and 30° north and south in the belt of the trade winds.
They are found in both the hemispheres pole ward of the tropical grasslands.

Question 46.
Name the parts that Sahara desert covers.
Answer:
Sahara desert covers :

(a) Parts of Algeria
(b) Libya
(c) UAR (Egypt)
(d) Sudan
(e) Mali
(f) Niger and Chad.

Question 47.
Where are the following deserts located ?

(a) Arabian desert
(b) Thar desert
(c) Kalahari desert
(d) Atacama desert

Answer:

(a) Arabian desert is to the east of Red sea.
(b) Thar desert is in the Indian subcontinent.
(c) Kalahari desert is in southern parts of Africa.
(d) Atacama desert is in South America extending along the Pacific coast to the west of the Andes mountains.

Question 48.
Mention the two features of the climate of tropical desert.
Answer:
The two features of the climate of tropical desert are :

1. Dry and hot
2. Aridity is the most outstanding feature of these deserts.

Question 49.
State the vegetation of deserts.
Answer:
Vegetation of deserts :

1. Cacti, thorny scrub and wiry grass, herbs, weed.
2. The vegetation may not appear green and fresh all the time.
3. Vegetation consist of entirely drought resisting plants – Xerophytes.
4. Dwarf trees like acacia are found.
5. Date palms are found near the oases.

Question 50.
Why are the deserts sparsely populated ?
Answer:
The deserts are sparsely populated because of the shortage of food and water.

Question 51.
Name the typical animal of desert region.
Answer:
Camel is the typical animal of desert region as it is especially well-adapted to the arid environment.

Question 52.
What is the location of Mediterranean region ?
Answer:
Mediterranean region is located on the western margins of the continents between 30 ° and 45 ° latitudes in both hemispheres.
It lies between the tropical deserts and cool temperate areas.

Question 53.
Mention the extent of Mediterranean type climate in the following :

(a) Asia
(b) Europe
(c) Africa
(d) America
(e) Australia

Answer:
Extent of Mediterranean type of climate is as follows :
(a) Asia includes :

1. Turkey
2. Syria
3. Lebanon and Israel

(b) Europe includes :

1. Spain
2. Portugal
3. Southern France
4. Italy and Greece

(c) Africa includes :

1. North-west Algeria
2. Tunisia
3. Morocco
4. Egypt and Southern Strip of South Africa.

(d) North America includes west coast of USA (a large part of California)
(e) Australia includes :

1. Southern and South-Western region
2. North Island of New Zealand.

Question 54.
What are the general characteristics of the climate of Mediterranean region ?
Answer:
General characteristics of the climate of Mediterranean region are :

1. A warm dry summer and a cool wet winter.
2. It receive moderate amount of precipitation.
3. Low humidity.
4. It experience many local winds-hot and cold.

Question 55.
Name the winds prevailing during summers and winter in Mediterranean region.
Answer:
During summer trade winds blow upto about 45° N latitude in the Northern Hemisphere. In winter the prevailing winds are westerlies and reach the western coasts of the continents as onshore winds. Being moist these winds cause rainfall in winter season.

Question 56.
What are the characteristics of the Mediterranean climate which makes it suitable for orchard farming ? Which state of USA is famous for orchard farming ?
Answer:
The Mediterranean lands are the well known orchard lands of the world. The mild rainy winters and abundant sunshine, even in winter, have made these regions very suitable for fruit growing. The state of California is famous for orchard farming.

Question 57.
Which country is the world’s leading producer of grapes?
Answer:
Italy is the world’s leading producer of grapes.

Question 58.
Why is the Mediterranean region popular for fruit processing industry ?
Answer:
The easy availability of fruit as a raw material leads the development of fruit processing industry. The popularity of viticulture witnessed a revolution in the manufacturing industry especially in the production of wines.

Question 59.
Why Mediterranean region cannot support large cattle populations ?
Answer:
Climate conditions in the Mediterranean region do not favour grasses because most of the rain occurs in cool season when the growth is slow. The only grasses that can grow in these regions are so wiry and bunchy that they cannot support large cattle populations.

Question 60.
During which season Mediterranean region receives most of its rainfall.
Answer:
Mediterranean region receives most of the rainfall in winter season.

Question 61.
Give the important evergreen coniferous trees of Mediterranean region.
Answer:
Evergreen coniferous trees of Mediterranean region are :

1. Pines
2. Firs
3. Cedars
4. Cypresses.

Question 62.
For what is California famous and why ?
Answer:
California is famous for orchard farming. It is because of its climate, long frost free growing season and fertile alluvial soils. Moreover there are many irrigation projects which provide plentiful supply of water to the farm lands.

Question 63.
Mention three special cultures of Mediterranean region.
Answer:
Three special cultures of Mediterranean region are :

1. Sericulture
2. Horticulture
3. Viticulture.

Question 64.
What is Viticulture ? Why is it so popular in Europe ?
Answer:
The cultivation of grapes is known as viticulture. This fruit is used for making wines of various brands and kinds. It is very popular in Europe because of its availability.

Question 65.
By what names are the grasslands known in following areas :

(a) In North America
(b) In South Africa
(c) In Hungary
(d) In Eurasia
(e) In Australia.

Answer:
The grasslands are known by different names in different areas :

(a) In North America as Prairies
(b) In South Africa as Veld
(c) In Hungary as Pastaz
(d) In Eurasia as Steppes
(e) In Australia as Downs.

Question 66.
Give the extent of steppes.
Answer:
Steppes extends from the east shore of the Black sea and Caspian sea to the Loess highland of north-west China, including the plain of Manchurian and Russian Turkestan.

Question 67.
What kind of climate does Steppe has ?
Answer:
It has continental climate. Extreme summer and winter temperatures.

• In Northern Hemisphere because of distance from sea summers are warm, winters are cold.
• In Southern Hemisphere climate is never severe. It is moderate because of nearness to sea.

Question 68.
What is the mean annual rainfall in Steppe region ?
Answer:
Mean annual rainfall in Steppe region is between 25 cm to 75 cm.

Question 69.
What is the extension of prairies ?
Answer:
Prairies extend from the Great Lakes to the Rocky mountains in Canada and the United States.

Question 70.
What is the average temperature and rainfall in prairies?
Answer:
The average temperature is 16°C and rainfall ranges between 50 and 75 cm.

Question 71.
Give the location of China type climate region.
Answer:
China type climatic region is located between 20° and 40° latitude in both the hemispheres along the eastern parts of the continents.

Question 72.
By which currents are the coastal parts of China type of climate affected ?
Answer:
The coastal parts of China type of climate are affected by the warm currents.

Question 73.
What are typhoons ?
Answer:
Typhoons are tropical cyclones which occur in China sea.

Question 74.
Give two characteristics of vegetation of China type climate.
Answer:
Dense forests of evergreen nature are found in more humid areas but areas of moderate rainfall are characterized by deciduous sparse forests and grasslands.

Question 75.
In which parts of Africa do tropical grasslands occur ?
Answer:
In the continent of Africa, the tropical grasslands are the most extensive, covering a belt around the Equatorial region in both the hemispheres.

Question 76.
What is known as ‘Parkland’ ?
Answer:
Some parts of tropical grasslands are known as ‘Parkland’ because there are clusters of trees, especially along river valleys and on the margins of the Equatorial region.

Question 77.
Why is the Taiga known as the Cold Pole of the Earth’?
Answer:
Taiga is known as the ‘Cold Pole of the Earth’ because Verkhoyansk (-68° C), the ‘Cold Pole’ of the world is located in this region in Eastern Siberia. It is a basin where the cold air stagnates for many weeks. It has the distinction of being the coldest place in the world.

Question 78.
Why is Polar Tundra region called the cold desert ?
Answer:
The Polar Tundra region is called the cold desert because the annual rainfall is less than 25 cm.

Give reasons for the following

Question 79.
There is little seasonal variation in the climatic condition of equatorial region.
Answer:
Due to almost vertical sun rays all the year round, there is little seasonal variation in the climatic conditions.

Question 80.
Equatorial regions support luxuriant vegetation.
Answer:
Equatorial regions support luxuriant vegetation because of high temperature and abundant rainfall.

Question 81.
Nights in the deserts are very cold.
Answer:
Temperature remains some what lower due to the influence of cold currents during night. Clear skies also cause a rapid cooling of the land at night.

Question 82.
Camel is called the ship of the desert.
Answer:
Camel is called the ship of desert because it has,adapted itself to the harsh environment of the desert in the following ways :

1. Its long legs with padded feet enable it to move fast over sand.
2. It can store water in its body for a number of days.
3. Its hump stores energy in the form of fat on which it can survive during times of starvation.
4. It is capable of picking very small leaves from even thorny bushes.
5. It has good capacity to carry loads.

Question 83.
Mediterranean regions receive most of their precipitation in winter season.
Answer:
In winter the prevailing winds are westerlies and they reach the western coasts of the continents as onshore winds. Being moist they cause precipitation on the western margin of the continents.

Question 84.
Climate conditions in the Mediterranean region do not favour grasses.
Answer:
Climatic conditions in the Mediterranean region do not favour grasses because most of the rain occurs in cool season when the growth is slow.

Question 85.
Agriculture is the main occupation of the people in most parts of the Mediterranean lands.
Answer:
Agriculture is the main occupation of the people in Mediterranean region. Long growing season, long hours of bright sunshine, the high temperature of summer, mid moist winters and fertile soils, in many areas, are favorable conditions for the growth of certain crops.

Question 86.
Grasslands are treeless.
Answer:
Grasslands are treeless because the porous soil and low rainfall mostly in summer. High evaporation and swift winds check the growth of trees in these regions.

Question 87.
The Steppe climate of the southern hemisphere is never severe rather it is moderate.
Answer:
The Steppe climate of the southern hemisphere is never severe rather it is moderate because of nearness to the sea.

Question 88.
The western margins of continents are extremely dry.
Answer:
The western margins of continents are extremely dry because the trade winds blow from the interior of continents as offshore winds.

Differentiate between the following 

Question 89.
Humid regions and Sub-humid regions.
Answer:
Humid regions :

1. Humid regions receive more precipitation than the evaporation all the year round.
2. These regions face no water deficiency in the dry season.

Sub-humid regions :

1. In a sub-humid regions the precipitation exceeds evaporation only during the short rainy season.
2. These regions face water deficiency in the dry season.

Question 90.
Humid regions and Arid regions.
Answer:
Humid regions :

1. Humid regions receive more precipitation than the evaporation all the year round.
2. No water scarcity.

Arid regions :

1. Arid regions precipitation is lower than the precipitation whole year.
2. Water scarcity throughout the year.

Question 91.
Warm temperate region and Cool temperate region.
Answer:
Warm temperate region :

1. It extends from 30° N to 45° N latitudes in each hemisphere.
2. It includes Mediterranean type, tropical desert type and monsoon type climatic region.

Cool temperate region :

1. It extends from 45° N latitudes in each hemisphere.
2. It includes west-European type, temperate grasslands, St. Lawrence type and Taiga type climatic region.

Question 92.
Sericulture and Viticulture.
Answer:
Sericulture :

1. Sericulture refers to the rearing of silk worms.
2. It is for. the production of raw silk. Leading producers are Northern Italy, Southern France and Parts of Spain.

Viticulture :

1. Viticulture refers to growing of grapes on a large scale.
2. It is for the production of wine. Leading producers are Italy, France, Spain and Portugal.

Question 93.
Truck farming and orchard farming.
Answer:
Truck farming :

1. The American farmers call ‘market gardening’as truck farming because they send fruits and vegetables daily to the markets by means of truck
2. Climatic condition is not an important factor in truck farming.

Orchard farming :

1. Mediterranean lands are the well-known orchard lands of the world. Orchard farming is concerned with growing of fruits on large scale.
2. Climatic condition is the main factor in orchard farming so lots of care is needed at every stage.

Question 94.
Evergreen and Xerophytic trees of Mediterranean region.
Answer:
Evergreen trees :

1. Evergreen trees of Mediterranean region have no regular season for shedding their leaves.
2. They have needle shaped leaves.
3. Pines, firs, cedars and cypresses are the main evergreen trees of this region.

Xerophytic trees :

1. Xerophytic trees of Mediterranean region they adapt themselves to the dry summer.
2. They have small, stiff, shiny leaves, thorns and long roots and waxy surface.
3. The vine (with long roots) laurel (with leathery leaves), cork oak with thick spongy bark are some examples of this region.

Question 95.
Role of trade winds and westerlies in Mediterranean region.
Answer:
Role of trade winds in Mediterranean region :

1. Trade winds prevail during summer.
2. These blow up to about 45° latitude.
3. These blow from an easterly quarter and become dry by the time they reach the western margins of the continents, cause no rainfall.

Role of westerlies in Mediterranean region :

1. Westerlies prevail during winter season.
2. These blow between 30° N latitudes.
3. These reach the western coasts as onshore winds. Being moist they cause precipitation on the western margin of the continents.

Question 96.
Steppes and Prairies.
Answer:
Steppes :

1. The grasslands in Eurasia are known as Steppes.
2. The Steppes of Eurasia occur on either side of the Ural mountains covering the parts of Eastern Europe and Western Siberia in Asia.

Prairies :

1. The grasslands in North America are known as Prairies.
2. Prairies of North America lie between the Rockies and the Great Lakes of North America.

Question 97.
Define Mangrove forest.
Answer:
Mangrove forest: These forests are found in the coastal areas and brackish swamps. The number of plant species found in any area in these forests are very large.

Question 98.
Define Shifting cultivation
Answer:
Shifting cultivation : It is a migratory system of agriculture. In this system, at first the small trees of an area are cut by a long thick bladed knife then, the slash is burnt, and crops are planted among the stumps by dropping the seeds into holes, made with a pointed stick.

Question 99.
Define Oases
Answer:
Oases : Oases are the areas in the deserts where some water is available. They are centers of greenery in the otherwise dreary expanse of the desert.

Question 100.
Define Sericulture
Answer:
Sericulture : It is an art of raising the silkworms and production of raw silk. Northern Italy, Southern France and parts of Spain are leading produces of silk in Europe.

Long Answer Questions

Question 101.

(a) Give a brief account of climate of the Equatorial region.
(b) Explain briefly the importance of Equatorial forests.
(c) Why are Equatorial forests not commercially important?

Answer:
(a) The Equatorial region is characterized by uniform high temperature and heavy rainfall throughout the year. This is why there is little seasonal variation in climatic conditions in this region.

1. This kind of climatic condition is due to the high angle of incidence of the Sun’s rays. The angle of incidence varies only between 66 V2° and 90° during the year.
2. Temperature ranges between 25° C and 30° C with an annual range of about 2° C.
3. Rainfall is well distributed during all the months of the year. The amount ranges from 150 cm to 350 cm or more. Rainfall is of Convectional origin. The intense heating of the atmosphere due to solar radiation causes convectional ascent of air leading to cooling of air condensation, formation of clouds and rainfall in the afternoon. But the mountain regions experience Orographic rainfall.
4. Thus the equatorial region has the combination of high temperature and high humidity but the climate is not unbearable because of cloudiness and heavy rainfall.

(b) Equatorial forests are important in many ways as :

1. They are very vital for our environment because they absorb a large amount of carbon dioxide from the atmosphere and exhale huge amount of oxygen. Hence they are known as the ‘Lungs of the world’.
2. They maintain the ecological balance so their destruction will adversely affect the ozone layer and cause a great harm to living beings.
3. They are the source of numerous medicinal plants and herbs, e.g., Quinine is obtained from cinchona tree growing in these forests.
4. They are a source of valuable hard wood timber like Mahogany, Ebony, Ironwood, Rosewood, etc.

(c) Equatorial forests are not commercially important because of the following reasons :

1. Equatorial forests are dense and have a large number of varieties of trees in mixed strands. Pure strands of trees are not found as in the coniferous forests.
2. Valuable species are found scattered over a large area.
3. The ground in damp and slushy and the construction of roads, railway line is difficult.
4. The climate is also oppressive due to high temperature, high humidity and heavy rainfall.

Question 102.
Explain the monsoon climate type region under the following heads :

(a) Temperature
(b) Air pressure and winds
(c) Vegetation
(d) Three seasons of Indian subcontinent.

Answer:
Monsoon climate type region under :
(a) Temperature : In summer, when the Sun is overhead on the Tropic of Cancer, the Northern Hemisphere is intensely heated. Summer temperature varies from 27°C to 30° C in the coastal areas and 35° C to 38° C in the interior.

1. In winter, the Sun is overhead on the Tropic of Capricorn. Temperature varies from 22° C to 25° C in the coastal areas and 15° C to 18° C in the interior.
2. In some northern parts of India the temperature during May and June becomes exceptionally high due to prevalence of hot winds locally known as loo.

(b) Air pressure and winds.

1. (i) The low pressure is strong enough to attract the moisture bearing winds from the Indian ocean.
2. (ii) The South East Trade winds from the Southern Hemisphere are drawn into India as the South-West monsoon winds after they cross the Equator.
3. (iii) Monsoon areas are affected by high and low pressure systems due to winter and summer seasons respectively.
4. (iv) There is complete reversal of pressure gradients over Asiatic landmass.

(c) Vegetation. Important trees :

1. Sal
2. Teak
3. Bamboo
4. Mahua
5. Jamun
6. Neem
7. Shisham, etc.

Trees are normally deciduous because of the marked dry season during which they shed their leaves to withstand the drought.
Forests are more open, less luxuriant. Tidal forests grow in Delta plains and along the coasts. The Sunderbans of Ganga – Brahamputra delta are famous mangrove forests.
(d) There are three main seasons in a year in Indian sub continent.

1. The hot, dry season is from March to mid June. During this period temperature is very high. Sun’s apparent movement is northwards to Tropic of Cancer. Relative humidity is low. Coastal region experiences some relief from the intense heat due to the moderating influence of the sea. Dust storms are very common in the northern region.
2. Humid warm summer season is also known as the rainy season which is from July to October. The maximum rainfall is concentrated in these months. Due to rains the temperature is considerably low.
3. Dry winter season from November to February. During this period North-East monsoon prevails. Winds are dry but over the Bay of Bengal they pick up moisture which is deposited in south-east Indian peninsula.

Question 103.

(a) Elaborate the special features of vegetation in hot desert region.
(b) What is the mode of rainfall in hot desert region.

Answer:
(a) The hot deserts are not good for vegetation due to climatic conditions. The rainfall is too scanty to support a vegetable cover. Therefore a lot of bare ground on desert land.

1. The type of vegetation growing here consists of thorny scrubs like cactus, prickly pear and other plants which are adapted to survive in a region of low rainfall. These are called Xerophytic plants.
2. Some species have thick leathery leaves, some are leafless while some plants have a repugnant smell so that they are not eaten by animals.
3. Cacti are the most typical plants of the deserts. The Saguaro Cactus in the Arizona Desert (USA) is the famous cactus.
4. The date palm grows best only in hot deserts as it requires plenty of sunshine and sandy soil. Date palms are grown near the oases where under ground water occurs near the surface.

(b) The hot deserts receive less than 25 cm of annual rainfall, on the average, but many places do not get even this because the hot deserts are located on western margins of continents and in the belt of Trade Winds. The trade winds become drier because the moisture gets precipitated on the eastern margins. The western margins are extremely dry because the Trade winds are blown from the interior of continents as offshore winds. The trade winds blow from cooler higher latitudes to warmer lower latitudes. Hence the winds gets warmed up and the possibility of rainfall is reduced. Rainfall occurs as torrential downpours associated with violent thunderstorms due to convectional ascent of air.

Question 104.
The Mediterranean land is known as the ‘Land of Orchards’. In this context answer the questions that follow :

(a) The characteristics of Mediterranean climate.
(b) How is it suitable for orchard farming ?

Answer:
(a) Characteristics of Mediterranean climate are as follows : These regions lie between the Tropical Deserts on the equatorward and cool temperate west margin region polewards. So the Mediterranean regions are characterised by warm, dry summer and cool wet winters.

1. It receives a moderate amount of precipitation as it is transitional between the arid and the humid regions.
2. The coastal regions are cooler than the interior ones due to the influence of cool ocean currents.
3. The humidity is low so the heat of the day is not felt oppressive.
4. The Mediterranean regions experience moderate rainfall only in winter and drought in summer. The annual rainfall varies from about 35 cm to 75 cm.
5. During the summer season, the North-East and South-East Trade winds prevail over this region. As these offshore winds are hot and dry, they blow dust from the adjoining desert regions.
6. During the winter season, this region is under the influence of the moist Westerlies blowing from the oceans. It gives much rainfall.
7. It experiences many local winds – hot and cold. The southern shores of Mediterranean sea are affected by hot and dry winds, called the Sirocco, which blow from the Sahara desert and carry a large amount of dust. The high temperature of the wind damages vine yards, olive trees and vegetable crops.
8. The hot and dry wind is known by many local names such as Khamsin in Egypt, Leveche in Spain and Santa Ana in California
9. Cold local winds called the Mistral descend from the Alpine range during the winter season and blow with great force which damage cultivated crops and trees.
10. A similar type of cold wind, called Bora, often causes devastation.
11. Clear sky and sunshine are common almost throughout the year.
12. Snowfall is very rare in this region except on mountains.

(b) Mediterranean land is suitable for orchard farming because of suitable climate. Orchard farming is important on the slopes which are not suitable for the cultivation of food crops. Fruit orchards cover large areas of hill slopes as citrus fruits trees have a deep root system to tap underground water. The climatic conditions of this region, the warm sunny summer, helps in ripening them. The mild rainy winters and abundant sunshine, even in winter have made these regions Very suitable for fruit growing. The dry season favour the harvest. Moisture deficiencies are avoided through good network of canals.
Some of the common citrus fruits are orange, lemon, lime and grape fruit. Other varieties are olives, grapes, peach, pear, plum, pomegranate, apricot and fig. Chestnut walnut, hazelnut and almond are also grown. Because of large scale fruit growing Mediterranean lands are the orchards of the world.

 

ICSE Solutions for Class 9 Geography – Preventive Measures

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
State two negative effects of vehicular emissions.
Answer:
Vehicular emissions have two negative effects on the environment : One is global climate change and the other is air pollution and its negative health repercussions.

Question 2.
Name any two gases emitted by vehicular emissions.
Answer:
Carbon monoxide (CO) and a large share of the hydrocarbonx (HC), nitrogen oxides (NO_x).

Question 3.
What is meant by carpooling ?
Answer:
Carpooling refers to the sharing of car journeys by persons travelling on the same route.

Question 4.
Name any three modes of public transport used in India.
Answer:
Buses, trams, passenger trains and metro rails.

Question 5.
What is a ‘No Smoking Zone’ ?
Answer:
Smoking does not just harm the smoker but also the people nearby, who breathe in the smoke exhaled by the smokers and are called ‘passive smokers’. Recent research has shown that concentration of second-hand tobacoo smoke (the smoke exhaled by smoekers) in many outdoor areas is often as high or higher than in some indoor areas and the risks posed by such outdoor exposure are well beyond generally ecceptd norms when large numbers of people are involuntarily exposed. Therefore, the passive smokers or those who unavoidably breathe in second-hand tabacoo at public places have such as lung cancer, asthma, bronchitis and sudden infant death syndrome in children.
To save such passive smokers and discourage smokers from the ill effect of the smoking in public places ‘No Smoking Zone’ has been created.

Question 6.
What are Fossil Fuels ?
Answer:
Fossil fuels refer to buried, combustible deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal and natural gas by exposure to heat and pressure in the earth’s crust over hundreds of millions of years.

Question 7.
State why should we use fossil fuels judiciously.
Answer:
Fossil fuels are non-renewable source of energy. As a result of growing demand fossil fuels are being depleted at a rate of 100,000 times faster than they are being formed. At the present rate of usage, the coal reserves are likely to last for about 200 years. Similarly, at the present rate of usage, the world’s crude oil reserves would be exhausted in just 50 years. These resources are non-renewable and take millions of years to form. It is essential, therefore, to reduce dependence on such energy resources and explore and exploit the enormous potential of alternative sources of energy like solar energy, tidal energy, wind energy, geothermal energy and biomass based energy. They are not only renewable sources of energy but are environmentally clean and safe to use.

Question 8.
State any three measures to save energy.
Answer:

1. Use extra blankets and sweaters instead of using room heaters. Likewise, in summer, dress in light, cotton clothes to save on air conditioning costs and energy.
2. Make sure that the houses are well insulated and, if heated or cooled, windows or doors are not left open. Raise shades on winter days, lower them in the summer. Seal all leaks. Block windows and doors with weather-strip tape and install blinds to reduce outside heat transfer.
3. Use a low-flow shower head, to reduce water consumption and energy usage to heat the water.

Question 9.
What is Organic Farming ?
Answer:
According to Food and Agricultural Organisation (FAO) “Organic agriculture is a unique production management system which promotes and enhances agro-ecosystem health, including biodiversity, biological cycles and soil biological activity, and this is accomplished by using on-farm agronomic, biological and mechanical methods in exclusion of all synthetic off-farm inputs”.

II. Long Answer Questions :

Question 1.
With reference to vehicular pollution in cities, state the significance of the following as a preventive measure.

1. Carpool
2. Public Transportation

Answer:

1. Carpool :
   (a) It reduces air pollution by reducing the number of vehicles on the road and thereby, cutting down the vehicular emissions.
   (b) It helps to save money in buying fuel and maintenance cost of cars.
   (c) It helps to save petrol and diesel and thereby, save foreign exchange that goes into buying these fuels.
   (d) It reduces traffic congestion on the roads and thereby prevents traffic jams, reduces fuel consumption and commuting time and the cost of road repairs.
   (e) It helps to use commuting time in useful pursuits.
2. Public Transportation :
   (a) It reduces damage to the environment by reducing emissions. For example, one bus emits far fewer fumes than 20 cars.
   (b) It requires 1/5 th energy per passenger per km compared to road based transport system. It therefore, reduces fuel consumption and thus helps to save foreign exchange used in buying petrol and diesel.
   (c) It causes less noise, no air pollution and is eco-friendly transport system.
   (d) It helps to save money spent on maintenance of personal vehicles. It avoids the need to find parking space for private vehicles. Thus, reduces congenstion on roads.

Question 2.
With reference to smoking, answer the following :

1. How does smoking harm passive smokers ?
2. Name any two legal provision meant to deter smoking.
3. State any three advantages of having a ‘No Smoking Zone’.

Answer:

1. Smoking does not just harm the smoker but also the people nearby, who breathe in the smoke exhaled by the smokers and are called passive smokers. Recent research has shown that concentration of second hand tobacco smoke in many outdoor areas is often as high or higher than in some indoor areas such outdoor exposure are well beyond generally are involuntarily exposed. Therefore, the passive smokers or those who unavoidably breathe in second-hand tobacco at public places have such as lung cancer, asthma, bronchitis and sudden infant death syndrome in children.
2. (a) As a preventive measure, a mandatory specific statutory health warning on cigarette packs was introduced in 1975. Realising the seriousness of the problem.
   (b) Smoking in public places was prohibited nationwide from October 2 under the Prohibition of smoking in Public Places Rules 2008. The smoking ban pertains to public places, which include auditoriums, cinemas, hospitals, public transport (aircraft, buses, trains, metros, taxis) and their related facilities (airports, bus stands, railway stations), restaurants, hotels, bars, pubs, amusement centers, offices, libraries, courts, post offices, markets, shopping malls, canteens, educational institutions and parks.
3. Advantages of No Smoking Zone are the following :
   (a) It reduces the possibility of second-hand tobacco smoke being inhaled by non-smokers.
   (b) It reduces air pollution. Areas which have prohibited smoking have been found to have better indoor air quality as opposed to areas where smoking is allowed.
   (c) It reduces healthcare costs by reducing the chances of diseases caused by smoking.
   (d) It reduces the chances of influencing others, especially the youth, to take on the habit of smoking.

Question 3.
With reference to Organic Farming state the following :

1. Four principles of Organic Farming.
2. Main characteristics of Organic Farming.
3. Importance of Organic Farming.

Answer:

1. The four Principles of Organic Farming are :
   (a) Organic should sustain and enhance the health of soil, plants, animals and humans as one and indivisible.
   (b) Organic farming should be based on living ecological systems and cycles, work with them, emulate them and help sustain them.
   (c) Organic agriculture should build on relationships that ensure fairness with regard to the common environment and life opportunities.
   (d) Organic farming should be managed in a precautionary and responsible manner to protect the health and well being of current and future generations and the environment.
2. The main characteristics of organic farming are the following :
   (a) Protecting the long term fertility of soils by maintaining organic matter levels, and creating optimized conditions for biological activity within the soil.
   (b) Providing crop nutrients indirectly using relatively insoluble nutrient sources which are made available to the plant by the action of soil micro-organisms.
   (c) Maintaining nitrogen self-sufficiency through the use of legumes and biological nitrogen fixation, as well as effective recycling of organic materials including crop residues and livestock manures.
   (d) Preventing weeds, disease and pests by relying primarily on crop rotations, natural predators, diversity, organic manuring, resistant varieties and limited (preferably minimal) thermal, biological and chemical intervention.
   (e) Providing attentive care and management of livestock, paying full regard to their evolutionary adaptations, behavioural needs and animal welfare issues, with respect to nutrition, housing, health, breeding and rearing.
   (f) Careful attention to the impact of the farming system on the wider environment and the conservation of wildlife and natural habitats.
3. Importance of Organic Farming are the following :
   (a) Organic faming promotes the use of crop rotations and cover crops, and encourages balanced host/predator relationships.
   (b) Organic residues and nutrients produced on the farm are recycled back to the soil. Cover crops and composted manure are used to maintain soil organic matter and fertility.
   (c) Preventative insect and disease control methods are practiced, including crop rotation, improved genetics and resistant varieties. Integrated pest and weed management, and soil conservation systems are valuable tools on an organic farm.

Practice Questions

Question 1.
What purpose does an electrostatic precipitator serve?
Answer:
It is a device which removes unwanted chemicals from smoke after combustion takes place. The negative charged dust particles are drawn towards positively charged particles collector surface and by knocking the plates particles fall into a hopper tray for disposal.

Question 2.
In the context of reducing air pollutions, give the advantages of changing the process ; maintaining and modifying existing equipment.
Answer:
Change of modify the process of production in order to lower the atmospheric pollutants for example :

1. The coal is washed before crushing it to reduce the fly ash emissions.
2. The process of absorption can be used to remove gaseous air pollutants. In this process, gaseous air pollutants are removed by dissolution into a liquid solvent like water or caustic or acid solution. Absorption is used to remove sulphur dioxide, chlorine, ammonia, nitrogen oxides and hydrocarbons.
3. The process of absorption can be used to remove pollutants from waste water. In this process the target pollutants are made to attach to the surface of activated carbon. This is done by producing carbon through combustion of coal, coconut shells, wood and other organic materials. This carbon is then reacted with steam or carbon dioxide to produce activated carbon. Adsorption helps to remove pollutants as well as bad tastes and odours from drinking water.

Question 3.
What is a scrubber ? With the help of a diagram show its working?
Answer:
It is a device that employs spray of water to catch pollutants

during emissions. In this process, water is introduced into a spray tower by means of a spray nozzle which allow downward flow of water. As the polluted gas flows upwards, the particulates present in the gas collide with the water droplets being sprayed from the spray nozzles. Under the influence of gravitational force, the liquid droplets containing the particulates settle at the bottom.

Question 4.
Describe with the help of a diagram, working of the settling chamber.
Answer:

This device consists of huge rectangular chamber with several . horizontal trays. The gas stream polluted with particulates is allowed to enter from one end. The horizontal velocity of the gas stream is kept low in order to give sufficient time for the particles to settle by gravity. The particulates having high density settle at the bottom of the chamber from where they are removed.

Question 5.
What care should be taken in order to reduce water pollution from non-point sources ?
Answer:
Non-point sources of pollution are the outside sources which affect a large area, e.g. run-off from agricultural fields and deforested areas. Run-off of manure should be diverted to the dry fields, there should be separate drainage for sewage to divert it with rainwater. Natural manure should be used and pest management system should be established for pest control to reduce the use of pesticides.

Question 6.
Briefly state the procedure of treating waste water by primary and secondary treatment. What happens in the tertiary treatment of waste water ?
Answer:
In primary treatment the run-off should be drained through screens, grit chambers and sedimentation tanks to remove toxic chemicals from the water.
In secondary treatment the waste water the primary treatment is brought into contact with sludge heavily laden with micro-organisms. Afterwards the air is passed to give oxygen to the micro-organisms which convert the organic matter into low – energy compounds. The sludge material settles down in the tank and the clean water can be used after treating with chlorine gas.
After primary and secondary treatments, pollutants such as phosphorus and nitrogen are removed, so that the water may be harmless to human health. It is called ‘Advanced Waste Treatment’.

Question 7.
Why is open dumping of solid waste not advisable ? What is done while segregating solid waste ?
Answer:
Open solid waste may pollute directly the air, besides this by washing with rainwater run-off it may pollute a large area and cause soil and water pollution. On the other hand the closed compost system of solid waste may provide good manure. Moisture control is done and micro-organisms help to stabilize the organic matter. First the fungi starts to work and at last actinomycetes break down the waste and convert it to humus known as compost making a good fertilizer.

Question 8.
“Better safe than sorry” is the guiding principle for control of Nuclear pollution. In this context answer the following :

• Explain-the three principles of radiation protection.

Answer:
These are :

1. keeping a distance from source of radiation
2. avoiding length of time of exposure
3. shielding the particular object and human body from the direct radiation.

• What should one do to protect oneself from radiation contamination ?

Answer:
Radioactive particles should not be inhaled by using air filters, using exhaust system is another method, wearing protective clothing prohibiting smoking are essential. Leakage of radioactive elements from nuclear reactors and plants should be checked regularly.

• How should the radioactive waste be stored and disposed of?

Answer:
Ans. Radioactive waste should be stored deep into the ground, where gradual decay may take place. High activity solid wastes could be packed in shielded containers, while low level liquid and gaseous wastes may be diluted before disposal for best possible safety.

ICSE Solutions for Class 9 Geography – Effects of Pollution

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
How does noise pollution affect animals ?
Answer:
Noise from industries, railways, crackers, explosions and commotion in the cities and aircraft, affect animals, birds, mice, fishes and domestic animals. Birds avoid migrating to places where noise level is above 100 dB. The noise emissions caused by supersonic aircraft and railways may cause miscarriage in mammals and fishes as well. Some of the birds have been found to have stopped laying eggs due to noise pollution

Question 2.
What major harm is done to the human beings by air pollution ?
Answer:
It causes irritation in eyes, nose, throat, asthma etc, headache, slurring of speech, lung cancer, damage to nerves, brain fiver and kidneys.

Question 3.
How are the animals affected by air pollution ?
Answer:
Polluted grass is eaten by the animals cause arsenic poisoning. Lead poisoning results in bronchitis and lack of appetite in pet animals.

Question 4.
What is the effect of oil spills on marine life ?
Answer:
Sea water polluted with oil leakage causes oil spills which contaminate sea water and lead to the death of marine organisms.

Question 5.
What causes waterborne diseases ? Name two waterborn diseases.
Answer:
Phosphates and Nitrates from fertilizers, industrial effluents e.g. Arsenic, Mercury, Cadmium, Lead etc. Gastrointestinal problems, typhoid etc.

Question 6.
In what way does soil pollution affect human beings?
Answer:
Human beings are affected through food chains e.g. Nitrogenous fertilizers produce toxic concentration of nitrate and nitrite in the leaves through soil, pollution of soil by underground water polluted by industrial wastes. Eutrophication causes pollution of water and soil making it infertile and unsuitable for plant growth.

Question 7.
Give the impact of radiations on the human body.
Answer:
Damage is caused to the offsprings and organs of the body. Several diseases are caused e.g., breast cancer, thyroid cancer, lung cancer, brain cancer and defective eye sight.

Question 8.
Why are nuclear radiations more dangerous than other forms of pollution ?
Answer:
Nuclear radiations survive for a long period upto hundred years resulting in widespread effects to pollute the natural environment.

Question 9.
What caused the Bhopal gas tragedy ?
Answer:
This was the worst industrial accident on December 3 1984, when about 40 tons of methyl isocyanate (MIC) leaked into the atmosphere from Union Carbides pesticide factory in Bhopal in Madhya Pradesh.

Question 10.
What caused the Chernobyl disaster ?
Answer:
This was a radioactive accident in 1986 in Chernobyl in Ukraine on April 26. When a reactor of nuclear power complex at Chernobyl exploded. A massive steam explosion, the core of the reactor combined with water to produce hydrogen exploded blowing toxic radioactive gases into the air.

Question 11.
What were the after-effects of the Bhopal gas tragedy?
Answer:
The tragic after effects were blinding people, choking their breathing and suffocating them, damaged the eyes, lungs and nervous system, upset the urine system and loss of unborn babies, different plant species were also damaged.

II. Long Answer Questions 

Question 1.
Noise pollution is detrimental to human health and environment. Discuss.
Answer:
Noise pollution has ill effects not only on the human beings but also on the environment. Human Health

1. Effect on hearing or Deafness : Continuous exposure to noise levels above 100 dB has an adverse effect on hearing ability within a fairly short time. Many workers who are exposed to the noise of jet aircraft or very noisy workshops for even moderate periods soon develop detectable hearing defects.
2. Effect on Communication : External sounds can interfere with conversation and use of the telephone, as well as the enjoyment of radio and television programmes.
3. Repeated interference with sleep : Different people have different depths of sleep and they can adjust to natural sounds. However, noisy conditions near residential areas at night causes difficulties in sleeping.
4. Mental or Physiological Effects : Many people complain that noise makes them mentally ill. Experiments have been performed to attempt to confirm or disprove these claims. Doctors and scientists have now medically confirmed that *noise disturbs the biological organisms and their respective functions.
5. Effects on Physical health and Psychological problems : Noise has little physical effect on the biological performance provided that the noise level is below about 90 dB. Damage to the inner ear may result if continuous noise levels exceed about 100 dB and can lead to physical illness. Psychiatrists and psychologists have in recent researches made observations that noise has certain relation with physical health causing tension resulting in problems such as speech interference, annoyance, fatigue, sleep interference and emotional distress.
   Effects on Environment : The noise booms cause cracks in national and archaeological monuments Very high levels of noise are the cause of cracks in hills. High intensity explosions can break glass panes and vibrations in the buildings.

Question 2.
How does air pollution affect human beings and environment
Answer:
Air pollution affects human health in various harmful diseases e.g. irritation in eyes, headache, vomiting, respiratory disease, cancer, damage to liver and kidneys. SO₂ causes harm to plants by yellowing the leaves, NO₂ causes suppressed growth of plants. Animals eating the polluted grass are affected with arsenic poisoning.
Soot, dust and fumes discolour the fabrics arid buildings. The Taj Mahal has suffered damage caused by SO₂ in the air by getting discoloured and corroded. SO₂ and H₂SO₄ causes corrosion of metals like steel, copper and zinc.

Question 3.
Explain how the accumulation of nutrients and chemicals in the water prove fatal for the marine organisms.
Answer:
Eutrophication causes in growth of phytoplankton and algae which reduce the penetration of oxygen, light and heat into the water bodies, so, the marine organisms suffer greatly and mostly die.

Question 4.
Explain with the help of a diagram how the accumulation of toxic substances increases as we move up the food chain.
Answer:
Nitrogenous fertilizers produce toxic concentration of nitrate and nitrite in the leaves, which are eaten by animals and as ; vegetables by men, which is very harmful for health. Eutrophication is dangerous to marine life and the secondary consumers eating fish etc. are also adversely affected through complicated diseases. Harmful pathogens are transferred to human through vegetables and fruits.

Question 5.
Explain the effects of soil pollution on human beings and environment.
Answer:
Soil pollution causes contamination of plants which may affect the human health and the scarcity of oxygen disturbs the natural composition of air and air pollution promotes unwanted diseases.

Question 6.
Explain with examples the effects of radiations on the environment and on humans.
Answer:
Radiations emitting from radioactive materials and the disposal of radioactive wastes cause pollution and damage the environment. The high level products of nuclear wastes remain in the environment for several hundred years. Radioactive threats to the environment are the accidents connected with the activities of nuclear reactors, nuclear-powered vessels and satellites, etc. On human being it causes genetic variations, and somatic variation i.e. damage to body organs, breast cancer, thyroid cancer, lung cancer, brain cancer and defective eyesight.

Question 7.
What was the immediate and long term effects of the leakage of MIC gas from the Union Carbide’s pesticide factory in Bhopal ?
Answer:
This accident killed 3500 people and 40,000 people were affected in an area of 100 sq. km. Gas leakage did the people blind, loss of body control, loss of unborn babies, damage to brain, kidney, lungs, intestinal diseases, damaging the reproductive ability and plant species.

Question 8.
What harm did radioactive pollution do in the Chernobyl disaster ?
Answer:
After the disaster, four square kilometres of pine forest near the reactor turned reddish-brown and died. Horses also died 6 km. away by thyroid damage whole of western USSR and other European countries are contaminated by gamma emitters deposited on the soil. Meat and dairy products were contaminated with Caesium-137. About 7,00,000 people became exposed to Chernobyl radiation, expecting bad health problems.

Question 9.
What Is the impact of toxic compounds on human beings ?
Answer:
Toxic Compounds :

• Mercury, Methyl mercury
• Heavy metals, Cadmium
• Arsenic
• Fluoride

Impact on Human beings :

• ‘Minamata’ disease in Japan.
• ‘ltai-itai’ disease in Japan.
• Cancer, ulcers, kidney failure.
• ‘Fluorosis’ discolouring of teeth.

ICSE Solutions for Class 9 Geography – Sources of Pollution

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Exercises

I. Short Answer Questions

Question 1.
Name any three air pollutants and the sources of each of them.
Answer:
Pollutant :

1. Carbon Monoxide (CO) :
2. Nitrogen Oxides (NO_x) :
3. Sulphur Oxides (SO_x) :

Sources :

1. Gasoline fuel, motor vehicles fuel, burning of wood and coal, solid waste disposal, Industrial processes.
2. Primary sources are motor vehicles and power generation stations, combustion of organic matters, furnace stacks, incinerators.
3. Mainly due to burning of coal, smelting operations, refineries, chemical plants, open burning of garbage and municipal incinerators.

Question 2.
What are natural sources of air pollution ?
Answer:
Natural sources are volcanic eruptions, sand, dust, forest fires etc.

Question 3.
Name one industry which pollutes the atmosphere with gaseous as well as with particulate matter.
Answer:
Automobile industry.

Question 4.
What is known as smog ? What harm is done by smog especially in winter ?
Answer:
Smog means smoke + fog. In winter season smog is responsible for many accidents due to the obstacle in visibility.

Question 5.
Name three gases emitted during burning of garbage.
Answer:
These are Carbon dioxide, Sulphur dioxide, Nitrogen oxides.

Question 6.
Mention any two sources of water pollution.
Answer:
Two sources of water pollution are :

• household detergents and sewage,
• oil spills

Question 7.
Name two heavy metals from industries that pollute water.
Answer:
Heavy metals are Lead and Mercury.

Question 8.
Mention any four sources of soil pollution.
Answer:
These are industrial wastes, domestic waste, chemical fertilizers and pesticides.

Question 9.
Why are radioactive pollutants very dangerous ?
Answer:
The emission of radioactive minerals Uranium 235 Plutonium 239, make the whole surroundings radioactive after fission and carried away by wind to long distances. These are dangerous to health, as these remain as it is for a long time.

Question 10.
What kind of solid and liquid pollutants does the offshore drilling produce ?
Answer:
Drilling produces dust, stones etc and crude oil spills pollute largely the oceanic water and disturb marine life.

Question 11.
What are primary pollutants ?
Answer:
The pollutants that are directly emitted from the sources and are found in the atmosphere in the form in which they are emitted are known as primary pollutants, e.g., ash, radioactive compounds, oxides of sulphur and nitrogen etc.

Question 12.
With an example, state what are secondary pollutants?
Answer:
The pollutants that are formed in the atmosphere by chemical interactions between primary pollutants and atmospheric constituents are known as secondary pollutants. Examples of secondary pollutants are Sulphur trioxide, Ozone, Peroxyacetyl Nitrate (PAN), Ketones etc.

Question 13.
What is the connection between urbanisation and air pollution ?
Answer:
The major connection between urbanisation and air pollution are automobiles, industries, burning of garbage and brick kilns. These sources release pollutants such as oxides of carbon, oxides of sulphur, oxides of nitrogen, and hydrocarbons, ozone, chlorofluoromethanes, etc.

Question 14.
How much are the automobiles responsible for air pollution ?
Answer:
Automobiles are mainly responsible for 80% air pollution, emitting Carbon monoxide, Hydrocarbons, Nitrogen monoxide etc.

Question 15.
How are brick kilns a source of gases and particulate matter that cause air pollution ?
Answer:
Brick kilns produce huge amount of Carbon oxides, smoke and dust etc.

II. Long Answer Questions :

Question 1.
With reference to noise pollution, answer the following:

1. How does traffic contribute to noise pollution ?
2. Why are the construction sites considered as worse than factories in their contribution to noise pollution ?
3. How do the airplanes cause noise pollution ?

Answer:

1. The increasing number of vehicles on the roads are a big source of noise pollution. Increasing traffic jams in congested areas lead to repeated hooting of horns by impatient drivers causing noise pollution.
2. Noise from construction sites is generally far worse than noise originating from factories. This is because whatever construction takes place noise emissions levels are higher as well as the equipment is inherently noisy.
3. Noise pollution caused by airplanes has been increasing steadily during recent years, especially in the areas close to international airports. This problem has mainly arisen because of the widespread use of heavy long-range jet aircraft. Noise made by jet planes is more disturbing than that of the old propeller driven aircraft because it is of far higher pitch. Jet noise is caused by the violent mixing of the jet of gases from the engine with the surrounding air. It is at maximum level during take-off when the engine delivers maximum thrust, and falls away rapidly as the aircraft climbs. During landing, the main source of high-frequency noise is the sound made by the air compressor and turbine blades. Aircraft pass close to the ground for quite a distance during the landing operation and this noise often constitutes a more sustained environmental nuisance than the intense noise of shorter duration produced during take-off.

Question 2.
Air pollution is the contamination of air by pollutants. In this context answer the following :
(i) How does the use of automobiles cause air pollution ?
Answer:
Automobiles produce large amount of CO, hydrocarbons, oxides and suspended particulate matter and cause air pollution.
(ii) Write short notes on industrial air pollution.
Answer:
Industrial pollution cannot be avoided, as without it development is not possible. So it is an unavoidable problem faced by urban industrial areas, because harmful gases, garbage etc. is emitted by industrial activities, e.g. Industries release CO, oxides of Sulphur and Nitrogen, smoke, dust etc. to the air.
(iii) What special kind of air pollution do the brick kilns produce?
Answer:
Dust and smoke are the main elements produced by the brick kilns to pollute the air.

Question 3.
With reference to the sources of water pollutants answer the following questions:
(i) Why is it harmful to dispose of household detergents in water bodies ?
Answer:
Detergents contain some phosphates which are helpful to 1 produce algae and aquatic weeds which pollute the water.
(ii) In what way does the industrial waste pollute water?
Answer:
Many harmful wastes are produced by the industries which ; pollute water, e.g. Kanpur leather works continuously are polluting water of Ganga river creating a big problem. Industrial wastes mixed with water make it poisonous and unhygenic and may result in various diseases.
(iii) How do the radioactive wastes get into the water bodies?
Answer:
Wastes produced by nuclear power stations nuclear weapons / testing, research laboratories, and hospitals, are the main radioactive wastes which pollute the water bodies.
(iv) How is the thermal pollution of water caused ? What are its effects ?
Answer:
The thermal power plants located near the rivers use water for cooling purposes. They release the recycled hot water into the rivers leading to thermal pollution. The hot water makes the temperature of aquatic environment rise which endangers the aquatic ecosystem.

Question 4.
Write short notes on soil pollution by

(a) Pesticides
(b) Biomedical waste.

Answer:

(a) Pesticide waste mixed with the soil make it harmful for natural composition of soil and natural plants which cannot be taken in food material due to toxic material and the soil is contaminated for a long time.
(b) Biomedical waste Hospital wastes contain organic materials, chemicals, metal, needles, plastics contaminate the soil and make it unfit for growth of plants etc. Third world countries are facing this problem deeply.

Question 5.
What are the sources of radioactive pollution ? Describe each of them.
Answer:
These are natural sources from cosmic rays, man-made sources by use of  X-rays, nuclear weapons, Atomic reactors and fuel, radioactive isotopes in research laboratories are the main reasons to pollute rivers, streams and lakes etc. through sewers.

Question 6.
What are the man-made sources of air pollution ?
Answer:
Man-made sources are human activities, e.g., industries, factories, urban settlement, aircraft, nuclear experiments, automobiles, agricultural and power plants etc. are the sources of air pollution.

ICSE Solutions for Class 9 Geography – Pollution

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Exercises

I. Short Answer Questions

Question 1.
What is environmental pollution ?
Answer:
Environmental pollution refers to any unfavourable alteration of our surroundings, wholly or largely as a by product of man’s actions. These changes may affect man and other organisms.

Question 2.
Give the definition of a pollutant.
Answer:
A pollutant is a product released into the biosphere disturbing the normal functioning of ecosystem due to its adverse effect on plants, animals and man.

Question 3.
Give the difference between natural and man-made pollutants.
Answer:
Natural pollution takes place by increasing the quantity of Carbon dioxide and Nitrogen oxide in the atmosphere but man made pollution is done by using pesticides, chemical fertilizers.

Question 4.
What is air pollution ? Give a source of air pollution.
Answer:
Air pollution is the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment. Air pollution is caused by addition of chemicals, carbon monoxide, sulphur dioxide, hydrogen sulphide by various factories, industrial plants.

Question 5.
Define water pollution.
Answer:
Water pollution is caused by contamination of water by alteration in physical, chemical, biological characteristics of water making it unsuitable for designated use in its natural state.

Question 6.
What is soil pollution ?
Answer:
Soil pollution is defined as the change in physical, chemical and biological conditions of the soil through man’s intervention resulting in degradation in quality and productivity of soil.

Question 7.
Why should we avoid soil pollution.
Answer:
Soil is the basic need of agriculture. If the soil is polluted, the crops will be harmful for health and quality.

Question 8.
What is radioactive pollution ?
Answer:
Radioactive pollution is done by cosmic radiation from space, terrestrial radiation from radio-isotopes from earth’s crust, nuclear fuels in atomic plants, atomic bombs etc.

Question 9.
What is noise pollution ? What harm does noise pollution do to human beings ?
Answer:
Noise pollution is done by extreme noise done by industrial sector, transport, loud speakers etc., which adversely affect human health causing severe headache, migraine, mental disbalance, nervous breakdown, heart diseases.

Question 10.
Give the difference between biodegradable and non- biodegradable pollutants.
Answer:
Biodegradable pollutants are degraded by microbial actions e.g. sewage, garbage etc, but non-biodegradable pollutants are not degraded e.g. glass, plastics etc.

Question 11.
Distinguish between each of the following :
(i) Biodegradable and Non-biodegradable Pollutants
Answer:
Biodegradable Pollutants :

1. These may be degraded ‘‘after sometime by biological or microbial actions.
2. These are sewage, domestic garbage of kitchen etc.

Non-biodegradable Pollutants :

1. These are not degraded by any biological or microbial actions.
2. These include plastics, pesticides and radioactive materials.

(ii) Quantitative Pollutants and Qualitative Pollutants.
Answer:
Quantitative Pollutants :

1. The excess of CO₂, Nitrogen oxide etc. pollute the atmosphere.
2. These create unhealthy atmosphere due to the scarcity of oxygen.

Qualitative Pollutants :

1. Use of pesticides, chemical fertilizers pollute the composition of atmosphere.
2. These result in various diseases, e.g. skin cancer asthma etc.

(iii) Natural Pollution and Anthropogenic Pollution.
Answer:
Natural Pollution :

(a) Cosmic radiation from space and terrestrial radiation pollute the atmosphere.
(b) It disturbs the natural atmosphere and harms human and animal life.

Anthropogenic Pollution :

(a) Man-made pollution is done by radioactive plants, atomic bombs, nuclear fuel etc.
(b) It creates various diseases cancer, heart problems, migraine etc, it also disturbs animal life.

II. Long Answer Questions

Question 1.
With reference to pollution, explain the following

(a) Air pollution
(b) Water pollution

Answer:

(a) Air pollution is the excessive concentration of foreign matter in the air which adversely affects the well-being of human beings, animals, plants and their environment. Air pollution is caused by addition of chemicals, carbon monoxide, sulphur dioxide, hydrogen sulphide by various factories, industrial plants.
(b) Water pollution is caused by contamination of water by alteration in physical, chemical, biological characteristics of water making it unsuitable for designated use in its natural state.

Question 2.
Explain clearly what is radioactive pollution. Why is radioactive pollution more harmful than other types of pollutions ?
Answer:
Radioactive pollution is caused by cosmic radiation from space, use of radioactive materials which are used in radioactive weapons, nuclear fuel and electric power.
Radioactive pollutants remain unperished for a long period, so these are more harmful to spoil natural environment. In t modem age, it has become very difficult to survive in natural state due to production of various radioactive materials for various purposes.

Question 3.
How is noise a source of pollution ? Why do we need to look at the problem of noise pollution seriously ?
Answer:
Noise is a source of pollution because noise pollution is done by extreme noise of industrial sector, transport, loud speakers etc., which adversely affect human health causing severe headache, migraine, mental disbalance, nervous breakdown, heart diseases.
Noise is a health hazard. Exposure to prolonged noise has many physical, physiological and psychological effects on human beings in the following ways:

1. repeated exposure to noise reduces the sleeping hours
2. productivity or efficiency of a human being
3. it affects the peace of mind and invades the privacy of a human being.

Question 4.
How are the pollutants categorised on the basis of their existence in nature. Give two examples of each category?
Answer:
Pollutants are categorises in mainly i.e. degradable and non- degradable pollutants, out of them non-degradable pollutants create problem of pollution, e.g. glass, plastics, pesticides etc.
On the basis of existence in nature, pollutants are divided into two categories:

• Quantitative pollutants : These substances exist in nature but they act as pollutants when their concentration or quantity increases up to a critical level in the atmosphere, e.g., Carbon- dioxide, Nitrogen oxide, etc.
• Qualitative pollutants : These pollutants do not exist in environment They are introduced into the environment through man’s activities, e.g., pesticides (DDT), chemical fertilizers, herbicides etc.

Question 5.
Explain with examples the difference between the primary and secondary pollutants.
Answer:
Primary pollutants are directly mixed with atmosphere e.g. smoke, ash, fumes, dust, CO₂ Sulphur dioxide Methane, Benzene etc. Secondary pollutants are created by automobiles e.g. Nitrogen oxides, hydrocarbons etc, which are more toxic than their original elements.

Question 6.
What is noise pollution ? How is it caused ?
Answer:
Noise pollution is defined as an unwanted sound that is an irritant and a source of stress.
Most of the noise originates from modem industrialised urban life. The main sources of noise pollution are :

1. Industrial Sector
2. Transport Sector
3. Household sector
4. Defence Sector
5. Loud Speakers
6. Miscellaneous Sources.

ICSE Solutions for Class 9 Geography – Humidity

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Exercises

I. Short Answer Questions.

Question 1.
Define the following terms :

(a) Precipitation
(b) Evaporation
(c) Condensation
(d) Humidity
(e) Latent heat.

Answer:

(a) Precipitation — It is process by which condensation in different forms falling on the ground e.g. rainfall, snowfall, drizzle, sleet and hail etc.
(b) Evaporation — It is the process of converting water into water droplets and vapour.
(c) Condensation — It is the process of converting the water- droplets into water.
(d) Humidity — It is the amount of moisture present in the atmospheric air.
(e) Latent heat — It is the unseen heat absorbed by the atmospheric air to form vapour after reaching boiling point of 100°C of water.

Question 2.
What determines the amount of water vapour in the air?
Answer:
The amount of water vapour or humidity is dependent on the temperature conditions, because the capacity of air to hold moisture changes according to the temperature, e.g., in higher temperature the water vapour amount may increase and in low temperature it may decrease.

Question 3.
How is relative humidity determined ?
Answer:
Relative humidity is the percentage of water vapour with respect to the amount of air at a particular temperature.

Question 4.
Name four chief forms of condensation.
Answer:
Four chief forms of condensation are clouds, fog, mist and dew droplets.

Question 5.
Mention the different forms of precipitation.
Answer:
Different forms of precipitation are rainfall, drizzling, hailstones, snowfall and sleet etc.

Question 6.
What do you understand by ‘condensation nuclei’ ?
Answer:
Condensation nuclei — Condensation nuclei is the base around which moisture is gathered and converts into a drop of water, e.g. the dust particles present in the atmosphere make the base of condensation form.

Question 7.
State the three types of rainfall.
Answer:

• Relief Rainfall – It occurs from the cooling of warm moist air which ascends above the mountain barrier lying in the direction of the prevailing winds.
• Cyclonic or Frontal Rainfall – It occurs when warm and cold air masses confront each other, the warmer air generally climbs above the colder air.
• Convectional Rainfall – Ascending currents of hot and humid air causes condensation of the clouds, resulting in heavy rainfall.

Question 8.
What is cyclonic rainfall ?
Answer:
Cyclonic rainfall is provided by the cyclones created in tropical and temperate regions along the air mass fronts, where warm and cold air meet together and the warm air is encircled by the cold air resulting in circular wind systems. The tropical cyclones provide heavy rainfall for a few days, but temperate cyclones provide light rainfall or drizzling for a long period.

Question 9.
How does latitude affect evaporation ?
Answer:
Evaporation is highest in the tropical belt due to continuous vertical rays of the sun, while in temperate belt less evaporation and in polar belt least evaporation takes place due to less insolation.

Question 10.
Why is evaporation maximum in tropical deserts surrounded by seas ?
Answer:
In tropical deserts, surrounded by seas, evaporation is maximum because of high temperatures and clear skies.

Question 11.
State the factors favouring evaporation.
Answer:
The conditions favourable for evaporation are high temperature and large amount of water of ocean, rainfall water etc.

Question 12.
What is the instrument used for measuring humidity?
Answer:
Hygrometer or Dry and Wet Bulb Thermometer is used to measure humidity.

Question 13.
State the process of clouds formation. Name the types of clouds.
Answer:
When the water vapour converts into the water droplets floating in the air, the clouds are formed. Main types of clouds are Cirrus, Cumulus, Altus and Stratus.

Question 14.
Name the regions which receive rainfall only in summer.
Answer:
The continental interiors in the sub-tropical regions get rainfall only in summer, e.g. Mangolia, Tibet etc.

Question 15.
Name two regions of heavy rainfall.
Answer:
Equatorial region and monsoon tropical region get highest rainfall. Highest rainfall is recorded in Cherrapunji and Mawsynram (1080 cm) in the world.

Question 16.
Describe the three chief ways in which condensation occurs.
Answer:
Three chief ways to assist condensation are :

1. High amount of moisture present in atmosphere.
2. The elements providing the nuclei for it should be present in atmosphere, e.g., dust particles, salt and smoke etc.
3. The air should be saturated i.e. the relative humidity must be 100% to create dew point or the temperature should be below dew point.

II. Give reasons for each of the following 

Question 1.
In Equatorial regions the sky often remains overcast with clouds.
Answer:
Due to excessive heat the evaporation takes place in fast speed, and in every afternoon rainfall occurs after heavy cloud formation by convection process. So the sky mostly remains overcast with clouds.

Question 2.
Human comfort depends on humidity.
Answer:
Human efficiency is best at 40% relative humidity. More or less humidity creates uneasiness of humidity and dryness.

Question 3.
Condensation is the reverse process of evaporation.
Answer:
Condensation takes place upto the dew-point comes, but after it precipitation starts due to water-droplets converted into water drops. So, condensation and precipitation are different processes occurring in different conditions and temperature episodes.

Question 4.
Coasts receive more rainfall than the interior of the continents.
Answer:
Moisture-laiden winds provide more rainfall to the coastal parts due to being situated by the coast and receiving the rain bearing winds, but the interior get negligible rainfall due to being the almost dry winds without moisture.

Question 5.
The windward sides of mountains receive more rainfall than the leeward sides.
Answer:
The windward sides of mountainous slopes get ample rainfall by striking with the rain bearing winds first, while the leeward sides cannot get sufficient rainfall due to being on other side where the winds become almost dry due to imparting rainfall in windward due to loss of major part of moisture and water drops.

III. Match the following

Answer:

IV. Long Answer Questions.

Question 1.
Distinguish between Absolute Humidity and Relative Humidity.
Answer:
Absolute Humidity :

1. It is the measure of the actual amount of water vapour in the air, regardless of temperature.
2. It is expressed as grams of moisture per cubic meter of air(g/m3).
3. The higher the amount of water vapour, the higher is the absolute humidity.
4. In weather calculations, absolute humidity is generally not taken into account.

Relative Humidity:

1. It measures water vapour in air but relative to the maximum vapour that the air can hold at that temperature.
2. It is expressed as the ratio (percentage value) between the absolute humidity of a given mass of air and the maximum amount of water vapour that it can hold at the same temperature.
3. Warm air possesses more water vapour than cold air, so with the same amount of absolute humidity, air will have a different relative humidity depending on temperature.
4. It is the essential characteristic of weather forecasts, which indicates the likelihood of precipitation, dew or fog.

Question 2.
With reference to condensation, define the following :

(a) Process of condensation.
(b) Atmospheric conditions that favour condensation.
(c) Forms of Condensation.

Answer:

(a) Condensation is the reverse process of evaporation. In condensation, water vapour in the atmosphere get converted into water droplets or ice. Condensation takes place when water vapour is added to saturated air or when the temperature falls below the temperature at which air become saturated.
(b) The atmospheric conditions that favour condensation are :

1. There should be a high amount of water vapour present in atmosphere.
2. Minuscule particles of dust, salt and even smoke act as condensation nuclei.
3. The temperature of air must be below dew point temperature so as to encourage condensation.

(c) Forms of condensation : Following are the forms of the

• condensation : Dew, frost, fog, mist, white frost and clouds. The clouds are formed when the temperature falls down below dew points, while dew, fog and clouds are formed when the temperature remains higher than the freezing point.
• Clouds : Clouds are formed when minute droplets of water vapour condense on a nuclei and remain suspended in air.
• Dew : When water vapour condenses on the surface, it forms tiny droplets of water called dew. Dew commonly occurs during winter on account of cooling of air below dew point.
• Frost : In very low temperature, when condensation occurs at zero metre or ground level, water vapour freezes into minute crystals of rice on objects near the ground such as blades of grass, leaves and tiny rock particles. Frost is harmful to plants.
• Fog and Mist : Fog and Mist are two related terms. Droplets of water suspended in the atmosphere close to the surface of the earth are termed as fog. On long winter nights, the ground cools more rapidly than the air above. Such cooling reduces temperature at the surface to below dew point. Water vapour at lower levels get condensed around minute solid particles to form fog.

PQ. Describe the process of evaporation together with factors that favour it.
Answer:
For evaporation excessive heat and presence of water bodies is essential. Nearly 600 calories of heat is required to change water into water vapour. Evaporation is maximum in tropical belt and mainly in hot desert region surrounded by water bodies. In the equatorial belt, due to overcast with clouds, evaporation is comparatively less due to obstacles of cloud in heating process.

Question 3.
Name the three types »of rainfall. With the help of a diagram describe each type of rainfall.
Answer:

1. Convectional rainfall : It occurs in the Equatorial regions. The high temperature leads to the rapid heating of air. Such heated air rises in convectional currents, leading to development of clouds at about 10 km height. Ascending currents of hot and humid air causes condensation of the clouds, resulting in heavy rainfall.
   
2. Relief Rainfall : Relief rainfall is also known as Orographic Rainfall. It occurs from the cooling of warm moist air which ascends above the mountain barrier lying in the direction of the prevailing winds. The presence of mountains causes humid jair to rise. The sudden ascent causes cooling of air, leading to condensation and precipitation.
   
3. Cyclonic Rainfall : This type of rainfall is due to cyclones and depressions. When warm and cold air masses confront each other, the warmer air generally climbs above the colder. The rising air is cooled while undergoing a frontal lift. This causes precipitation.
   

Question 4.
Define precipitation. Write short notes on three forms of precipitation.
Answer:
The process by which products of condensation, viz water droplets, ice crystals, sleet, etc., fall to ground is known as precipitation. Rainfall, snowfall, drizzle, sleet and hail are the chief forms of precipitation. Precipitation takes place only when they particles of water join together to form large sized particles which become too heavy to remain in suspension in the cloud.

1. Rain : It is the most common form of precipitation. Raindrops of smaller size and less intensity are known as drizzle.
2. Dew : When water vapour condenses on the surface, it forms tiny droplets of water called dew. Dew commonly occurs during winter on account of cooling of air below dew point.
3. Frost : In very low temperature, when condensation occurs at zero metre or ground level, water vapour freezes into minute crystals of ice on objects near the ground such as blades of grass, leaves and tiny rock particles. Frost is harmful to plants.

Question 6.
Make a brief survey of the world distribution of rainfall.
Answer:
Equatorials and coastal areas of monsoon countries get maximum rainfall, more than 200 cm, sub-tropical areas get moderate rainfall 100-200 cm, and the least rainfall areas are Hot and cold deserts getting nearly 25 cm.

ICSE Solutions for Class 9 Geography – Atmospheric Pressure and Winds

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Exercises

I. Short Answer Questions.

Question 1.
Define the following terms :

(a) Pressure Gradient
(b) Winds
(c) Coriolis force.
(d) Altitude
(e) Monsoons.

Answer:

(a) Pressure Gradient — It is the rate of change of atmospheric pressure between two points on the earth’s surface.
(b) Winds — Horizontal movements of the air from high pressure to low pressure areas are called winds.
(c) Coriolis force — This force is created by the rotation of the earth as the winds in different belts deflect towards right in Northern hemisphere and to the left in Southern hemisphere.
(d) Altitude — The pressure also decrease with increasing altitude at the rate of 100 millibars in every 1000 metres of height gained.
(e) Monsoons — are the periodic seasonal winds blowing in the regions of South East Asia and Northern Australia. The word monsoon is derived from the Arabic word ‘Mausim’ meaning ‘Season’, on account of deeply affecting the seasons of the particular region.

Question 2.
Name the four main pressure belts of the earth.
Answer:

• Equatorial low pressure belt
• Sub-tropical high pressure belt
• Circum-polar low pressure belt
• Polar high pressure areas.

Question 3.
What is Circum-polar Low Pressure Belt ?
Answer:
It is the belt of low pressure belt between 60°N – 70°N and 60° S – 70° S.

Question 4.
How does Coriolis Force vary latitudinally ?
Answer:
In the northern hemisphere the winds deflect towards right and in Southern hemisphere deflect towards left due to the effect of the rotation of the earth, e.g. the trade winds take the Southwest direction in place of southern direction in northern tropical belt and in southern tropical belt these winds take northwest direction in place of northern direction.

Question 5.
Name the three chief types of wind.
Answer:
Three chief types of winds are Trade winds, Westerlies, and Polar winds.

Question 6.
What are periodic winds ?
Answer:
Periodic winds blow at regular intervals or in regular cycles. They are winds that result from localised differences in pressure and temperature. For example, land and sea breezes and the seasonal winds.

Question 7.
What are local winds ? Name any two local winds.
Answer:
The local winds blow in certain places and these are warm and cold according to the area from which they blow, e.g. Foehn winds blow descending on the slopes of the Alps and makes the temperature ideal for grapes due to its warm effect. In the same way Chinook winds blowing and coming down from the Rockies mountains in North America helps to increase the temperature and are beneficial to keep grasslands ice free and warms the ranches, so good for animal rearing.

Question 8.
Name two types of variable winds ? Why are they so called ?
Answer:
Variable winds change their direction and force from place to place due to changing the pressure system. These blow for a short time or for a few days. These are cyclones and anticyclones. These are the circular winds with low pressure and high pressure in the centre respectively.

Question 9.
Why are cyclones frequent in summer in the tropical region ?
Answer:
In summer in the tropical region due to die shifting of Doldrums, the low pressure region is strongly originate between 8° and 20° N and S. They mainly originate in China sea and surrounding area. In Bangla Desh, these are known as ‘KalBaisakhi’ rneaning ‘Time of Death’ and cause heavy calamities and destruction. These are known as ‘hurricanes’ in North America, ‘Typhoons’ in China,‘willywillies’ in Australia.

Question 10.
Mention any two differences between Tropical Cyclones and Temperature Cyclones.
Answer:
Tropical Cyclones :

1. Tropical cyclones are produced mainly over the sea.
2. They generally originate in the tropical region between 8° and 20°N and S.

Temperature Cyclones :

1. Temperate cyclones are produced both on land and on sea.
2. They originate in the mid latitudinal region between 35° latitude and 65° latitude.

Question 11.
How are cyclones named differently in different parts of the world ?
Answer:
The name of the cyclones is different in different parts of the world on the basis of the local languages e.g. hurricanes in America, typhoons in China and Japan, meaning the destructive horrible cyclonic winds.

Question 12.
What are two chief characteristics of anticyclones ?
Answer:
Two chief characteristics are that these provide clear weather and the winds blowing from the centre towards outside in clockwise direction.

Question 13.
Why are the summer monsoons known as South-West Monsoons in the Indian subcontinent ?
Answer:
Due to the low pressure created in the Northern Indian subcontinent and high pressure centre located in the Indian ocean, the Monsoons start to blow from the ocean to the Indian landmass taking a direction from southwest to northeast in summer seasons.

Question 14.
Name the two types of instruments used for measuring pressure. State one point of difference between them.
Answer:
Two types of barometers are used for measuring pressure, e.g. Fortin’s Barometer and Aneroid Barometer. The main difference is that Fortin’s Barometer is filled with mercury, while Aneroid Barometer is without any liquid. Fortin’s Barometer consists of a long narrow tube filled with mercury, while Aneroid is in the round shape like a watch.

Question 15.
Briefly state the variations in the vertical distribution of pressure.
Answer:
Many factors like slope of land, presence of winds and the temperature affect the pressure of air vertically. The rate of decrease is 100 millibars per 1000 metres of height gained. There is a thin air cover at high altitudes, so the percentage and amount of oxygen is also less.

Question 16.
Why are the months of January and July used to describe the world distribution of pressure ?
Answer:
Due to the lowest and highest temperatures recorded in January and July respectively the pressure areas are also affected, so it is preferred to display the distribution of pressure distinctly in January and July.

II. Give reasons for each of the following

Question 1.
The Westerlies in the Southern Hemisphere blow with greater force than those in the Northern Hemisphere.
Answer:
In the Southern Hemisphere there is open ocean for free movement along the belt of Westerlies. These blow with roaring sound and great speed along 40°S. and are known as ‘Roaring Forties’.

Question 2.
There is a seasonal shifting in pressure belts.
Answer:
Due to the earth’s changing aspect with respect to the sun, the pressure belts shift northwards by 5° in summer and southwards in winter resulting in particular seasonal changes, e,g. The cold waves blow in India in winter due to the sub¬tropical belt shifting along 30°N touching the Himalayas. On the other hand in summer the trade winds become powerful in India and push the monsoon winds from east to west in Northern Plain of India.

Question 3.
As we go higher, the atmospheric pressure decreases.
Answer:
As the air become thinner with increasing height, so, the air pressure also decreased. The rate of decrease is 100 millibars per 1000 metres of height gained. So mountain hikers take oxygen cylinder with them to compensate the air inhaled.

Question 4.
The winds are directed to the right of their flow in the Northern Hemisphere.
Answer:
Due to the rotation of the earth from west to east, the winds are deflected to the right e.g. the trade winds blowing from north, to south take north easterly direction.

PQ. Mediterranean lands receive most of the rainfall in winter season.
Answer:
Mediterranean lands come along the belt of Westerlies along 30°S in place of 40°N in winter. So, the Mediterranean countries along 30°N get ample rainfall. Similarly in the Southern Hemisphere the Westerlies blow along 30°S, in winter, so, the southern Mediterranean countries get winter rainfall.

Question 5.
Temperature and pressure are inversely related to one another.
Answer:
When the temperature increases and the air start to rise upwards. creating a low pressure area, but when the temperature decreases, the air start to sink downwards creating a high pressure area on land surface. So, the temperature and pressure are inversely related to one another.

Question 6.
Humid air is lighter than dry air.
Answer:
In tropical region the air is greatly humid due to excess of evaporation creating a low pressure conditions, while the cold regions with less humidity are high pressure areas. So, the humid air is lighter than dry air.

Question 7.
Doldrums is a low pressure belt.
Answer:
Doldrums is a low pressure belt along the equator from 5°N to 5°S. In this belt due to high amount of evaporation, the atmosphere is very calm and quiet due to no circulation of winds and continuous rising air mass creating a hollow like condition in this belt. Inspite of air pushed towards the equator, it is immediately deflected to right and left, creating a vacuum like condition resulting in a belt of calm named as ‘Doldrums’

III. Distinguish between the following

PQ. Isobars and Isotherms
Answer:
Isobars :

1. These are the lines joining the places of same air pressure.
2. The closeness of these lines indicate the intensity of pressure.

Isotherms :

1. These are the lines joining the place of same air temperature.
2. The closeness of these lines indicate the intensity of temperature.

Question 1.
Cyclones and Anticyclones.
Answer:
Cyclones :

1. These are the circular winds with low pressure in the centre.
2. The winds blow anticlockwise from outside to the centre in Northern Hemisphere.
3. These bring rainfall, clouds thunder lightening.

Anticyclones :

1. These are circular winds with high pressure in the centre.
2. The winds blow clockwise from the centre towards all sides in Northern Hemisphere.
3. These bring clear weather and cold winds.

PQ. Vertical and Horizontal Temperature variation.
Answer:
Vertical Variation :

1. The Temperature decreases as the height increases
2. The rate is 1°C for every 166 metres of height.

Horizontal Variation :

1. The temperature decreases as the latitude increases.
2. Highest temperatures are found along Equatorial and tropical regions, while least temperature is recorded in polar areas.

Question 2.
Permanent and Periodic Winds.
Answer:
Permanent winds :

1. These blow throughout the year.
2. These are named Trade winds, Westerlies and Polar winds.

Periodic winds :

1. These blow in particular area and seasons.
2. These are named monsoon winds, Chinook, Foehn, Mistrel winds etc.

Question 3.
Summer and Winter Monsoons.
Answer:
Summer Monsoon :

1. These blow in summer season from July to September.
2. These bring heavy rainfall with thunder lightening

Winter Monsoon :

1. These blow in winter mainly in December and January.
2. These bring dry cold weather and cold waves.

IV. Long Answer Questions.

Question 1.
What is meant by the term ‘Atmospheric Pressure’ ? Explain briefly the factors that affect Atmospheric Pressure.
Answer:
Atmospheric Pressure refers to the force per unit area exerted against a surface by the weight of the air above that surface. Pressure is expressed in millibars (mb) and measured with a mercury barometer. The average atmospheric pressure at sea level is 1013.25 mb or 760 mm (the) height of the column of mercury in a barometer at sea level). Atmospheric Pressure decreases with height.
Factors affecting Atmospheric Pressure are as below :

• Altitude : The atmospheric pressure decreases with height or altitude. The decrease in pressure is about 1 cm of mercury for every 110 m of ascent. The atmospheric pressure is highest at sea level. This is because at higher altitudes the air is thinner or less dense than the air at the sea level. The maximum air density is at the earth’s surface ; air density decreases with height because the pull of the earth’s gravity is less. The fewer number of gas molecules at higher altitudes means fewer molecular collisions and a decrease in air pressure.
• Temperature : Atmospheric pressure decreases with increase in temperature. This is because when the temperature rises, air expands. The molecules of air move far apart (become less dense) and hence exert less pressure. On the contrary, with decrease in temperature the air gets compressed and the space between molecules decreases (becomes more dense) and exerts more pressure on the region.
• Water Vapour : Water vapour concentration affects atmospheric pressure because the molecular weight of water (18 g/mol) is less than the average molecular weight of air (about 29 g/mol). When water evaporates and enters the atmosphere as a gas, the water vapour molecules take the place of other gas molecules in the air. So, a volume of wet (or humid) air weighs less than an equal volume of dry air. Therefore, humid air is less dense and exerts less pressure than dry air.
• Rotation of the Earth : Due to the rotation of the earth, bulk of the air at the Poles is thrown away towards the Equator. Since the Equatorial region receives great amount of heat throughout the year, the air becomes warm and light and therefore, it rises and creates low pressure. At the Poles, the cold heavy air sinks down and creates high pressure. In fact, temperature and rotation of the earth together contribute to the formation of world pressure belts.

Question 2.
Explain the swinging of the pressure belts.
Answer:
In summer the pressure belts are pushed northwards and in winter southwards.

This shifting takes place upto 5° distance. In summer, it results in remarkable change in weather and climate, e.g. summer monsoon with thunderstorms, lightening and rainfall etc. while, in winter, the Mediterranean climatic regions get rainfall due to Westerlies coming from sea towards land.

Question 3.
Briefly explain the three chief types of winds.
Answer:
The three chief types of winds are Trade winds, Westerlies and polar winds.
Trade winds : blow along the tropical belt from sub-tropical High to equatorial low pressure belts. The name trade is given due to the past time, when trade ships were sailed according to the direction of these winds.
Westerlies : are the winds blowing from western direction. These are south-westerly in northern and north-westerly in the southern hemispheres.
The Polar : winds are icy cool winds blowing from poles towards Circum polar low pressure belts, which are also known as Blizzards.

Question 4.
Describe some of the important types of local winds.
Answer:
Chinook in North America blowing eastwards from the Rockies slopes make the climate of Central Plains ideal for animal rearing and agriculture.
Foehn : winds descending down from the Alps makes the agriculture successful in PO basin and
Mistral : from the Alps along France towards the Mediterranean sea brings the temperature suddenly down instead of bright sunshine.

Question 5.
Explain the weather conditions associated with tropical and temperate cyclones.
Answer:
Tropical cyclones : These are associated with turbulent weather conditions and cause heavy damage to property and human life, e.g. Tornado in North America, Hurricanes in Carribean region, typhons in China and Japan. These blow from south to north.
Temperate cyclones : These are active along mid-latitude region from west to east direction and cover a long region. These are pushed with Westerlies and also called the western Disturbances. These affect from Mediterranean to Pacific ocean covering South European countries, Middle East, Iran, Iraq etc., Pakistan, India, China from west to east. These are associated with rainfall, snowfall, hailstones etc, followed by a clear weather due to coming back anticyclones.

Question 6.
What are the Jet Streams ? What is the significance of Jet Streams ?
Answer:
Jet streams are the concentrated bands of rapid air movement found in troposphere and stratosphere. The meeting front of warm and cold winds along sub-tropical zone near 30° latitude and polar front along 60° latitude. Jet streams transport moisture and help in formation of cyclonic winds. Jet streams are used to forecast the weather specially for air travel, so that the flying should be done according to the jet-streams. Mostly, these jet-streams blow from west to east with the Westerlies.

Question 7.
Describe the world distribution of pressure.
Answer:
The distribution of atmospheric pressure across the latitudes is termed as global horizontal distribution of pressure and represented as pressure belts, e.g. Equatorial low, Sub-Tropical High, Circum-polar low and Polar High pressure belts. It is correlated with the rising up and descending down of the air along low and high pressure belts respectively. Due to the spherical shape of the earth the higher latitudes receive less insolation than the lower latitudes and this difference in temperature different pressure belts are created. Due to extreme low pressure equatorial ‘Doldrums’ (still air) are created.

ICSE Solutions for Class 9 Geography – Insolation

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
What is solar radiation ? What is its significance for the earth ?
Answer:
The sun continuously radiates heat and light energy in all the directions. It is known as solar radiation. Solar radiation is the only primary source of light and heat on the earth. The earth receives its heat from solar radiation which is a tiny fraction of the radiated energy of the sun.

Question 2.
What is meant by insolation ? State two of its main characteristics.
Answer:
The amount of solar energy received by the earth is called insolation, but only one part out of two billion parts reaches the earth. So, out of total 100% solar energy only 51% reaches the earth, 35% reflected back to into space and only 14% is absorbed by the ozone layer.

Question 3.
State two advantages of convectional heating of the atmosphere.
Answer:
Convectional heating of the atmosphere is done by heating up the layer of air touching land surface and rising up to warm up the upper layer, while the cold wind sinks down and again heated up by the terrestrial radiation. This circulation causes formation of clouds, rainfall and mild changes in climatic behaviour.

Question 4.
Name four factors that affect the temperature of a place.
Answer:
The four factors that affect the temperature of a place are :

1. Latitude
2. Distance from the sea.
3. Altitude
4. Wind direction
5. Natural vegetation

Question 5.
How does the distance from the sea affect the distribution of temperature ?
Answer:
Due to the physical property of water, which is heated up and cooled down slowly with respect to the land. So, the coastal areas experience mild climate with least range of temperature, while the regions far from the sea are affected by extreme climate with maximum range of temperature.

Question 6.
State the pattern of temperature in mid latitudes.
Answer:
Due to spherical shape of the earth, temperature zone gets less insolation resulting in moderate climate with normal temperature ranging from 15°C to 30°C. The duration of sunshine is greater in summer than winter. So the summer is warm and winter is cold.

Question 7.
How would the breezes that blow during the day and those that blow during the night affect the temperature of a place situated in the coastal region ?
Answer:
During the day the sea breeze blowing from sea towards land keeps the coastal region cool and during the night land breeze blowing from land towards sea makes the sea cooler. This interchange of breeze maintains the heat balance resulting in the mild climate of the coastal regions with lower daily and annual ranges of temperature.

Question 8.
What difference is there in the temperatures on a mountain and on a sea shore ?
Answer:
The rate of decrease of temperature is 1°C for every 166 metres, the temperatures on a mountain are for lesser than the temperatures on a sea shore which is nearly at zero height.

Question 9.
Why is India cooler in December than in July ?
Answer:
Tropic of Cancer passes midway across India, so, there is summer season in July, while in December the sun is vertical on the Tropic of Capricorn in southern hemisphere, so India experiences winter season. So naturally December is cooler than July.

Question 10.
State two chief characteristics of the Temperate zone.
Answer:
Medium temperature and medium rainfall due to slanting rays of the sun and less evaporation.

Question 11.
Explain the following:

(a) Diurnal range of temperature.
(b) Mean Monthly Range of Temperature.
(c) Mean Annual Range of Temperature.

Answer:

(a) Diurnal range is the difference between the maximum and minimum temperature within 24 hours, of the day.
(b) It is the difference between the mean maximum and mean minimum temperatures within the month.
(c) It is the difference between mean maximum and mean minimum temperatures within a year, mainly between June and January.

Question 12.
Define briefly ‘Heat Balance”.
Answer:
Heat balance is defined as the state of equilibrium that exists on earth between incoming insolation from the sun and the out going terrestrial radiation from the earth.

Question 13.
Name the heat zones of the earth.
Answer:
Torrid zone, Temperate zone and Frigid zone.

II. Distinguish between each of the following
Answer:
Insolation and Terrestrial Radiation.
Insolation :

1. It is the incoming solar radiation intercepted by the earth.
2. It travels in short waves.
3. Insolation involves only 51 units out of 100 units of solar radiation.

Terrestrial Radiation :

1. It is the earth’s radiation given back to atmosphere and space.
2. It travels in long waves.
3. Out of 51 units of insolation 34 units are transferred to the atmosphere and 17 units go back to space.

Question 2.
Land Breeze and Sea Breeze.
Answer:
Land Breeze :

1. It blows from Land to sea.
2. It blows at night.
3. It makes the sea water cooler.
4. It moderates the temperature of sea.

Sea Breeze :

1. It blows from sea to land.
2. It blows in the day time.
3. It makes coastal parts warmer
4. It moderates the climate of the coastal parts.

Question 3.
Torrid and Temperate Zones.
Answer:
Torrid Zone :

1. It lies between 23 1/2° N and 23 1/2° S
2. It receives highest temperature and rainfall.
3. It receives the vertical sun’s rays.
4. Equatorial region and the tropical belt receive maximum insolatioa

Temperate Zone :

1. It lies between 23 1/2° N and 66 1/2° N & 23 1/2° S and 66 1/2° S
2. It receives medium, temperature and rainfall.
3. It received slanting rays of sun.
4. Due to spherical shape of the earth, this zone received quite less amount of insolation.

Question 4.
Annual Range and Monthly Range of Temperature.
Answer:
Annual Range of Temperature :

1. It is the difference between the highest and lowest temperatures within one year.
2. It is the difference between the highest temperature of May-June and lowest temperature in December January, i.e. the temperature difference between summer and winter.

Monthly range of Temperature :

1. It is the difference between the maximum and minimum temperatures within a month.
2. Mostly the middle of month is noted for maximum and end of the month records minimum temperatures.

III. Give reasons for each of the following

Question 1.
North India has a greater range of temperature than South India.
Answer:
North India comes in temperate zone, while South India comes in Torrid Zone situated in the North and South of Tropic of Cancer. So North Indian places have greater range, which is greatest in the Desert of Rajasthan.

Question 2.
The temperature of Delhi is less than that of Chennai in December.
Answer:
Delhi is far from sea, while Chennai is situated along the coast of Bay of Bengal. So Delhi is colder than Chennai in December.

Question 3.
Distance from the sea affects the temperature of a place.
Answer:
Warm effect of sea keeps the temperature less in summer and higher in winter, e.g. Bombay (Mumbai) is wanner than Delhi in winter.

Question 4.
Land is heated and cooled faster than the sea.
Answer:
In the desert of Rajasthan range of temperature is highest due to the physical property of land to be heated and cooled down quickly with respect to the sea. So, the temperature difference is least at Mangalore and Chennai.

Question 5.
The temperature of a place depends largely upon its latitude.
Answer:
As the rays of the sun become more and more slanting with increasing latitudes. So the tropical region never gets snowfall, while the polar region is always frozen.

Question 6.
Desert areas experience a high day temperature and a much lower night temperature.
Answer:
Desert areas are covered with large sand plains. The physical property of the sand is to heated up quickly and cooled down abruptly ; so the day temperature is very high and the night temperature is very less.

Question 7.
The ports of the western coast of Europe remain ice- free during winter.
Answer:
Due to the warm effect of the Gulf Stream and North Atlantic Drift the ports of Western Europe remain ice free in winter to motivate successful international oceanic trade, e.g., London, Calais, Lisbon, Amsterdam, Brest, Le Havre etc.

PQ. The earth’s surface receives only about 51% of the Solar energy.
Answer:
Out of 100 units, only 51 units are received by the earth as isolation, while 35 units are reflected back by atmospheric layers, clouds, snowfields and 14 units are absorbed by ozone layer.

Question 8.
The vertical rays of the sun give more insolation than the slanting rays.
Answer:
Tropical region gets vertical rays of the sun and receive much heat providing high temperature while the temperate and polar regions have less temperature due to slanting rays of the sun.

Question 9.
A desert region has a high range of temperature than a forest region.
Answer:
A desert region gets highly heated and quickly cooled down due to the sand cover; while the forested region most of the solar energy is used in transpiration in vegetation realm and do not become very hot. On the other hand due to the emission of carbon dioxide by plants the temperature is maintained due to the heat absorbing property of CO₂.

IV. Long Answer Questions

Question 1.
Describe the four factors that affect the distribution of temperature.
Answer:
The factors are different physical properties of land and water keeping continental climate cold and oceanic climate mild
Latitude The temperature decreases from the equator towards poles.
Distance from the sea keeping coastal ports mild and areas for from sea cold.
Altitude mountains are cooler than plains due to the lapse rate of decrease of temperature of 1°C for every 166 m. of height; Slope of the land South facing slopes of mountains are warmer than northern facing. Inversion of temperature takes place in hilly valley regions due to higher sunny slopes and the valley downward covered with fog and snow are cooler than higher slopes.
Wind direction Windword slopes get much rainfall, while the Leeward slopes are drier.
Natural vegetation cover absorbs 90% of solar energy, which is again consumed in transpiration and keeping the forested are mild, while snowy lands are cold.
Cloud Cover and Humidity: Clouds reflect the sunlight leaving the land below cool. Still, the humidity absorbs heat keeping these areas with average temperatures not more than 30°C.

Question 2.
Explain the effect of latitude and ocean currents on the temperature of a place.
Answer:
The Tropical areas are far warmer than the polar areas due to difference in the angle of incidence of the rays of the sun. Ocean currents greatly affect tire climate of a place or region e.g. the European western coast enjoy ice-free coasts and developed navigation due to the warm, effect of Gulf Stream – North Atlantic Drift, while the cold current of Benguala keeps the warm South African coast cool and mild.

Question 3.
Describe the heat budget of the earth.
Answer:
Heat budget is actually the Heat Balance of incoming and outgoing radiation.
The incoming solar radiation comes towards earth in short waves and provides heat to the earth as insolation in the day and again this insolation is given back by terrestrial radiation at night. This balance is called heat budget.

Question 4.
State how the Global Heat Balance is achieved ?
Answer:
Out of 100 units of solar radiation 35 units are reflected back by atmospheric layers and clouds and snowfields etc, 14 units are absorbed by the ultra-violet rays in ozone layer and only 51 units are received by the earth as insolation and again these 51 units are reflected back by terrestrial radiation out of which 34 units are absorbed by the earth and sent back to atmospheric layers and 17 units radiated back into the space. This process is called the Heat budget or Global Heat Balance.

Question 5.
With the help of a diagram, show the heat zones of the earth and write briefly about each of them.
Answer:

1. Torrid Zone : It lies between 23 1/2° N and 23 1/2° S latitudes. This zone receives maximum temperature due to vertical rays of the sun and maximum rainfall.
2. Temperate Zone : It lies between 23 1/2° N – 66 1/2° N and 23 1/2° S – 66 1/2° S. It is known for medium temperature and rainfall due to slanting rays of the sun.
3. Frigid Zone : It lies between 66 1/2° N – 90° N and to 66 1/2° S – 90° S. The sun’s rays are slanting and have to cover a very large distance. Besides this, inspite of long summer covering 6 months, the sun’s heat is immediately reflected back by the snow cover. So, the temperature is extremely low and cold Blizzards (icy winds) blow from Poles towards Arctic and Antarctic circles. The coldest place on the face of the earth is Varkhoyansk (-58°C) in N.E. Siberia. Although the temperature in Antarctic may be -94°C, but there is no habituated place, (as the definition of a place is the area inhabited by people).
   

Question 6.
Study the table and answer the following questions :

1. Calculate the mean annual temperature
2. Calculate annual range of temperature
3. Name the hemisphere in which it is located. Give reasons to support your answer.
   

Answer:

1. Sum of the temperature of hottest month of the year 4.4 + 10.0 + 13.3 + 16.0 + 15.0 + 10.0 + 5.0 = 73.7 Sum of the temperature of coldest month of the year
   
2. Annual range of temperature = Highest temperature in a month of year – Lowest temperature in a month of year = 16°C – 2°C = 14°C
3. It is located in Northern hemisphere :
   The Reason is due to the Earth’s Axial tilt, in the Northern hemisphere winter lasts from the winter solstice (typically December) to the March Equinox (typically March). While the summer lasts from the summer solstice (typically June) through the autumnal Equinox (typically September).

Question 7.
Name four factors that affect the temperature of a place.
Answer:
Four factors are :

1. Distance from equator
2. Distance from sea
3. Altitude from the sea-level
4. Slope of the land.

Question 8.
Describe world temperature patterns and its three chief characteristics.
Answer:
The world distribution of temperature generally shows a decreases in insolation from the Equator towards the poles. But this pattern is not everywhere the same. Three chief characteristics are the distance from the sea, physical properties of land and ocean (water), Height from the sea level.

Question 9.
Explain the ranges of temperature and show their calculation.
Answer:
The Diurnal range is calculated by subtracting minimum temperature from the maximum temperature within 24 hours or of one day. The Mean monthly range is calculated by subtracting the mean minimum temperature from mean maximum temperature within 30 days or a month. Annual range of temperature is calculated by subtracting the mean minimum temperature from the mean maximum temperature within one year i.e. mostly between June and January.

V. Practical Exercises

Question 1.
Draw a labelled diagram showing the heat budget of the earth.
Answer:

Question 2.
Calculate the mean annual temperature and annual range of temperature of the following station and name the hemisphere in which it is located.
Answer:
Mean annual temperature is 3.5°C.
The range of temperature is 20°C.
It is located in Northern hemisphere.

Practice Questions (Solved)

Question 1.
State the importance of insolation.
Answer:
Importance of insolation The radiant energy received by the earth from the sun is called the incoming solar radiation or insolation. The insolation received by the earth is responsible for all forms of activity on the Earth. The circulation in the atmosphere is due to the differential heating of the atmosphere by insolation. The radiant energy from the sun enables plants to manufacture their own food. This forms the basis for food needed by all other organisms on the Earth. The circulation of ocean water is also due to the unequal heating of the ocean water by insolation.

Question 2.
Why does only 51% of the insolation reach the Earth’s surface ?
Answer:
Only 51% of the insolation reaches the earth’s surface because 35% is reflected back into space by the atmospheric layers and 14% is absorbed by the atmosphere.

Question 3.
What do you understand by daily range of temperature and annual range of temperature ?
Answer:
The difference between the maximum and minimum temperature recorded in a particular day at a place is called daily range of temperature. It is low in coastal areas while it is high in deserts and in interiors of continents.
The difference between the mean temperature of the hottest month (July) and mean temperature of the coldest month is called the annual range of temperature. It is low equatorial region, while it is high in polar areas.

Question 4.
Define the following :

(a) Daily Mean Temperature.
(b) Monthly Mean Temperature.
(c) Annual Mean Temperature.
(d) Mean Temperature of a place.

Answer:

(a) Daily Mean Temperature — The average of the maximum temperature and minimum temperature recorded during a day (24 hours) is known as daily mean temperature.
Daily Mean Temperature

For example, if a place has the maximum temperature of 39°C and minimum temperature of 27°C for a particular day, the daily mean temperature.

(b) Monthly Mean Temperature — The average of the daily mean temperature of all days of a month is known as monthly mean temperature.
Monthly mean temperature of July

(c) Annual Mean Temperature — The average of daily mean temperature of all days of a year is known as Annual mean temperature.
Annual mean temperature of year 2010

(d) Mean Temperature of a place — Mean temperature of a place is obtained by collecting the data for a period of 30 – 40 years. The average of mean annual temperature of a place is calculated. This is also known as normal temperature of a place.
Mean temperature

Question 5.
Distinguish between maritime climate and continental climate.
Answer:
The nearness to sea has a moderating influence on the temperature of coastal areas. Maritime or equable temperatures are found in coastal areas. But extremes of temperatures, with a continental climate, are found in inland areas remote from the sea. Due to the presence of land breezes and sea breezes in coastal areas : the summers are warm and winters are cool. This is due to the differential heating and cooling of land and water. Land surfaces are heated more quickly than water. But a greater annual range of temperature is found as we go away from the equator. The climate of Mumbai is more equable than that of Delhi.

Question 6.
Explain the importance of insolation.
Answer:
Sun is the most important source of atmospheric heat. Sun’s diameter is more than 100 times the Earth’s diameter and has a surface temperature of more than 10,000 °F. The heat waves radiate from the sun in all directions at a speed 186,000 miles per second of 3 lakh km per second. The solar radiation received by the earth is 1/2000 millionth part of solar output. Yet, this small amount is vital for our existence on the earth. It is estimated that, on the average the earth receives about 1.9 g calories per minute per sq. cm. This is known as ‘solar constant’. All the physical phenomena depend upon insolation. Winds and ocean currents originate due to insolation. The earth is habitable only due to insolation.

Question 7.
Explain the Greenhouse effect of atmosphere.
Answer:
Atmosphere is heated by the radiation from the earth’s surface below. This action is compared to that of a glasshouse of greenhouse in which vegetable and flowers are grown in polar areas. Glasshouse permits radiation to get in but does not allow radiation to escape out. Therefore, glasshouse is warmer from inside than outside. Atmosphere also acts like a blanket keeping the earth warm. It is known as greenhouse effect of atmosphere. This is due to presence of carbon dioxide in atmosphere. Carbon dioxide has the ability to absorb earth radiation. The carbon dioxide layer acts as a glass roof of the greenhouse. With the increase in carbon dioxide, the temperature of the earth is increasing. Due to this, the year 1955 was the hottest year in India during this century.

Question 8.
What is global warming ? What are its causes ? State its effects.
Answer:
Global warming : The burning of fossil fuels, (coal, gas, petroleum), the cultivation of soil, large scale industrialisation, rapid means of transport and deforestation has caused an imbalance in the atmosphere. These activities are increasing the amount of carbon dioxide. Thus, greenhouse effect has raised the average, temperature of the earth by 0.5°C. By the year 2000, the earth’s, average temperature will go up by 2°C. This is called global warming. Global warming is causing a rise in sea-levels due to melting of glaciers. It is threatening to submerge many coastal areas.

Question 9.
Mountains are cooler than plains. Discuss.
Answer:
The temperature decreases with height at the rate of 1°C per 165 metres or about 0°C per kilometre. The atmosphere is heated by radiation from the earth below. Therefore, lower layers are warmer than higher layers. There is absence of water vapour and dust particles on high mountains. So there is unchecked radiation. That is why mountains are cooler than plains. Shimla is cooler than Delhi. Similarly, Nainital is cooler than Allahabad.

Question 10.
“Winter nights at Delhi are cooler than in Mumbai”. Why?
Answer:
Mumbai has an equable climate due to coastal location, while Delhi is an inland town. The presence of land and sea breezes keep the nights warm at Mumbai.

Question 11.
Vertical rays are Hotter than slanting rays. Why ?
Answer:
Vertical rays are hotter than slanting rays due to the following reasons:

• Vertical rays heat up a smaller surface. Hence, the heat received per unit of area is large. On the other hand, slanting rays heat up a large area.
• Vertical rays travel through a shorter distance in the atmosphere and the loss of heat is less. Slanting rays travel a longer distance through the atmosphere where much of its heat is absorbed by clouds, water vapour and dust particles.

Question 12.
Why is noon hotter than morning and evening ?
Or
Maximum temperatures are found in the afternoon. Why?
Answer:
The sun is overhead at noon. The Sun rays are almost vertical. But in the morning and evening, the angle of Sun rays is oblique. Slanting rays fall in the morning and evening. Vertical rays are hotter than slanting rays. As the vertical rays give more heat per unit area, the noon is hotter than morning and evening.

Question 13.
‘Despite its location in higher latitudes, the coast of Norway is never frozen.’ Why ?
Answer:
The areas situated in higher latitudes have a cold climate. In winter, these areas have temperatures below freezing point (0°C). But coast of Norway is never frozen. Its ports are ice free. North Atlantic Drift (Gulf Stream currents) flows along its coast. It is a warm current which raises the winter temperatures of this area.

Question 14.
Why are the northern slopes of Himalayas cooler than its southern slopes ?
Answer:
The Northern Slopes of Himalayas are away from the Sun. These slopes get oblique rays. These slopes are exposed to cold winds. These are shady slopes and are cooler. But the Southern Slopes are Sun facing slopes. These get Sun’s rays more directly and also for longer periods. These are Sunny slopes and shelters from cold winds. So the Southern Slopes of Himalayas are warmer than northern slopes.

ICSE Solutions for Class 9 Geography – Composition and Structure of the Atmosphere

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
What is known as atmosphere ?
Answer:
The blanket of air upto 1500 km surrounding the earth is known as atmosphere.

Question 2.
State the gaseous composition of the atmosphere.
Answer:
The atmosphere consists of 78% Nitrogen 21% oxygen and 1% other gases.

Question 3.
Mention any three functions of the atmosphere.
Answer:

1. Air has weight and exerts pressure. Being pressed down it always remains in contact with land and water.
2. Due to their physical contact, exchange of gases between air, land and water takes place on a continuous basis.
3. Soil absorbs oxygen and nitrogen due to this contact. Water vapours in air rise from oceans on account of evaporation.

Question 4.
Name the four layers of the atmosphere.
Answer:
Four layers of the atmosphere are :

1. Troposphere
2. Stratosphere,
3. Mesosphere
4. Thermosphere.

Question 5.
What is known as troposphere ?
Answer:
Troposphere is the lowest and densest layer of atmosphere touching the land surface. It extends from 8km to 18 km. in height

Question 6.
Mention the chief characteristics of stratosphere.
Answer:
There is total absence of water vapour in this layer. It extends upto a height of 50 km. The temperature remains constant up to – 55°C.

Question 7.
In which layer of atmosphere do all weather conditions occur ?
Answer:
Troposphere is the layer where all weather conditions occur in different forms.

Question 8.
Name the constituent gases of atmosphere which scientists consider responsible for climate change.
Answer:
Carbon dioxide and ozone are responsible for climate change, as carbon dioxide absorbs heat from sun and by radiation from the earth; ozone absorbs extremely hot ultra-violet rays controlling the ideal temperature conditions on the earth.

Question 9.
What is known as ozone layer ?
Answer:
Stratosphere contains sufficient amount of ozone which absorbs the extremely hot ultra-violet rays of the sun. It is known as ozone layer.

Question 10.
What is leading to depletion of ozone layer in the atmosphere ?
Answer:
Excessive emission of carbon monoxide and CFCs from industries and vehicles take out the oxygen from ozone layer to form different compounds (oxides). In this way the depletion of ozone layer takes place.

Question 11.
What is known as Global Warming?
Answer:
Global Warming is the increase in temperature of earth due to enhanced concentration of Greenhouse gases (CFCs) in the atmosphere.

Question 12.
Name important Greenhouse gases.
Answer:
The main Greenhouse gases are CFCs (Chlorofluorocarbons) and nitrogen oxides which are emitted by fertilizers industries and transport engines along with carbon dioxide and methane.

Question 13.
Name two chief characteristics of atmosphere.
Answer:
Atmosphere protects earth from harmful ultra-violet and infra-red rays of the sun. It controls the hydrological cycle and provide life giving gases.

Question 14.
What keeps the atmosphere in a dynamic state ?
Answer:
The atmosphere protects the earth from harmful ultraviolet and infrared rays of the sun. It has oxygen and nitrogen, the life sustaining gases. It helps in retaining the necessary warmth on the earth and helps in the circulation of water vapour as the source of rainfall. These functions of atmosphere keep it in a dynamic state.

Question 15.
What is called weather ?
Answer:
Weather is the physical condition or state of atmosphere (temperature, pressure, state of sky etc.) at a given locality or an area.

II. Explain the following terms/processes in detail

1. Global Warming
2. Greenhouse Effect
3. Normal Lapse Rate of Temperature
4. CFCs

Answer:

• Global Warming : The temperature on the earth is rising. This phenomenon known as Global Warming is the result of enhanced concentration of Greenhouse gases in the atmosphere caused mainly by human activities. Consequences of Global Warming:

1. Global temperature is likely rise by 2 to 5°C during the next century. Due to rise in temperature by 2 to 5°C, there is a chance of melting of ice caps on Earth’s poles. This melting of ice will result in the rise of the sea level. Large stretches of low lying areas will submerge and many island countries will face deep encroachment by sea water. Some may disappear altogether.
2. As the increase in temperature will be uniform all over the surface of the world, there will be serious climatic changes. This will bring various changes in wind and rain patterns.
3. Higher temperature will cause rise in transpiration, which in turn, will affect the groundwater table.
4. As the climatic belts shift from equator towards pole, the vegetation would also shift away from the equator.
5. Insects and pests will increase in the warmer climatic conditions. Thus, pathogenic diseases will multiply.

• Greenhouse Effect: Greenhouse are built in cold areas to grow the plants within it in warm temperature. But, due to Global Warming the whole earth is becoming a Greenhouse due to increase in temperature, which indirectly disturb the normal life on earth by challenging nature and nature will originate many unwanted problems of change in climate, radiation imbalance, diseases etc.
  The rate of absorption of solar radiation by earth and its emission back into space as infra-red waves balances the heat on earth. This phenomenon plays a very important role in maintaining surface temperature of earth. The carbon dioxide and other gases form a blanket around the globe which prevent the passage of infra-red waves from earth back into space. Concentration of solar radiation produces much heat, making earth a very warm place. This phenomenon is similar to that of greenhouse in which the glass enclosed area gets heated up due to its insulation from the rest of the environment. Hence, warming of the atmosphere is due to the greenhouse effect. Hence, Global Warming is also known as Greenhouse Effect.
• Normal Lapse Rate of Temperature : The decrease in Temperature is known as normal lapse rate, which is calculated as average decrease of 1°C for every 166 metres altitude gained. The lapse rate works mainly in troposphere which results in various types of weather and climatic changes affecting the life on earth.
• CFCs : (Chlorofluorocarbons) are organic compounds that contain carbon, chlorine, fluorine produced as volatile deriatives of methane and ethane which catalyze the conversion of ozone (O₃) into O₂, while O₃ is more powerful to absorb ultra-violet rays than that of O₂. So CFCs disturb the ozone layer which is so essential for earth.

III. Long Answer Questions

Question 1.
Describe the structure of the atmosphere.
Answer:
In the atmosphere, there are concentric layers of air. Each layer has different density. The upper layers press down the lower one. So, the air of the lower layer is always heavier or denser, while the upper layers are thinner or less dense. In this way about 90 per cent of the mass of air lies within a height of about 20 km from the surface of the earth.
On the basis of the characteristics of temperature and air pressure there exist four thermal layers of the atmosphere. They are — Troposphere, Stratosphere, Mesosphere and Thermosphere. The Thermosphere is divided into Ionosphere and Exosphere.

Question 2.
How does atmosphere govern life on earth ?
Answer:
Stratosphere absorbs the harmful ultra-violet rays of the sun and the troposphere regulates all weather conditions e.g. ideal temperature, rainfall and their impact on human life.

Question 3.
Explain the factors responsible for depletion of ozone in atmosphere.
Answer:
Various occupations related to industries, transport and fertilizer cause large amount of CFCs emission along with nitrogen oxide and methane have disturbed the ozone layer depleting the oxygen particles. Volcanic eruptions emit sulphur dioxide creating harmful chemical reactions which dismantle the ozone layer.

Question 4.
Give a description of the recent studies about Global Warming.
Answer:
The Global mean temperature has increased by 0.6°C in the 20th century. It is estimated to increase by 1.4° to 5.8°C by the year 2100 from 1990. This has affected abnormal weather conditions in various parts e.g. less rainfall in Africa and Gulf Coast of U.S.A., more rainfall in Asian tropical region and some areas may get no rainfall. Increasing melting of ice and glaciers resulted in rise of oceanic water level by 10 to 25 cm. Warming of atmosphere will considerably increase its moisture carrying capacity. While the troposphere warms up, the stratosphe will cool down.
It is the balance between radiation coming into the atmosphere and radiation going out. Any change in this balance can have rapid impact on life forms on earth because it will have an impact on the sensitivity, adaptability and vulnerability of the whole biospheric system.
Climate change will bring about substantial changes in cereal production specially in the Tropics. Global freshwater conditions may worsen by 2025.

Question 5.
Why should we protect the atmosphere ?
Answer:
Atmosphere is necessary to sustain life on earth, because without atmosphere there would be no oxygen, no weather changes, rainfall etc, which are essential for activities of human life and ideal temperature on the earth.
The atmosphere protects the earth from harmful ultraviolet and infrared rays of the sun. It has oxygen and nitrogen, the life sustaining gases. It helps in retaining the necessaiy warmth on the earth and helps in the circulation of water vapour as the source of rainfall. These functions of atmosphere keep it in a dynamic state.

Question 6.
What is known as the Antarctic ozone hole ?
Answer:
Ozone hole above the Antarctic region was detected by NASA in the USA. This is due to the emission of CFCs etc. and absence of vegetation cover along Antarctic. CFCs deplete the ozone amount and there is no oxygen addition due to absence of vegetation realm.

Practice Questions (Solved)

Question 1.

(a) What is ‘Atmosphere’ ?
(b) Explain the composition of the Atmosphere ?
(c) Name different layers of atmosphere. Describe the important characteristics of each layer.

Answer:

(a) The earth is surrounded by a coverage of air which extends to height of several hundred kilometres. This is called the atmosphere. Near the surface of the earth, the air is dense, as we go up higher, the atmosphere gets more and more rare field. About half the air composing the atmosphere is found within 5 kilometres of the earth surface.
(b) The most important gases composing the atmosphere are nitrogen 78% and oxygen (21%). Therefore, 99% of the atmosphere consists of nitrogen and oxygen. Of the remaining gases, argon accounts for 0.9%. The other gases are carbon dioxide, helium, hydrogen, methane, etc. These gases are called the fixed components of the atmosphere, because their relative proportion is constant in the lower layers of the atmosphere. In addition to fixed components, there are a number of variable components of the atmosphere. The quantity of these components varies from place to place.
(c) The atmosphere is composed of the following belts (layer):

1. Troposphere : This atmospheric layer lies closed to the earth’s surface. It extends to a height from 8 km (Near the Poles) to 18 km (Near the Equator). Most of the weather phenomena occur in this layer of atmosphere. It is a dusty zone containing much water vapour and clouds.
2. Stratosphere : The next layer lying above the troposphere is the stratosphere. The thickness of this layer varies about 62 km (at the Equator) and about 72 km (at the Poles.) Temperature is almost constant. There is no clouds, water vapour of dust in this layer due to constant temperature in the vertical direction. Ozone gas is found in abundance which absorbed harmful ultra-violet radiation from the sun.
   
3. Mesosphere : This third layer is above the stratosphere. ‘Meso’ meaning the intermediate, this region is marked by decrease in temperature with height. Temperature decrease from about 0°C at Stratopause to 100°C at Mesopause. This inversion of temperature is probably due to absence of ozone molecules beyond the stratosphere. This layer extends to 80 km. above the’earth.
4. Thermosphere : It lies above the Mesosphere and is divided into two parts-the Ionosphere and Exosphere.

• Ionosphere : The air layer lying behind the stratosphere is known as the Ionosphere. This extends to a height of 80 km to 480 km. Radio waves used in long distance radio communication are reflected back to earth by Ionosphere. In this way, radio massages can be transmitted round the curve of the Earth. This is about 970 km thick.
• Exosphere : The upper-most layer of the atmosphere is called Exosphere. It lies somewhere between 480 km. and above the Earth. It is known only to aerospaceships.

Question 2.
What is the significance of solid particles in the atmosphere ?
Answer:
The solid particles present in the atmosphere are of dust, smoke, pollen grains and emissions released from chimneys of factories.
Significance : The solid particles present in the atmosphere act as nuclei or the condensation of water vapour around them.

Question 3.
What is the significance of Ozone and what are the effects of its depletion ?
Answer:
Ozone in the atmosphere acts as a protective umbrella for us by absorbing harmful ultraviolet radiation coming from the sun.
Effects of Ozone depletion :

1. The ozone layer screens out more than 99 percent of the incoming solar energy. Ultraviolet radiation of these wavelengths are harmful to most forms of terrestrial life, causing eye irritation, skin cancer and many other diseases, depending on the amount of radiation.
2. It impairs the growth of certain crop plants and adversely affects a wide variety of organisms from bacteria to vertebrates.
3. Micro organisms may undergo a high rate of mutation because of high sensitivity of the DNA to ultraviolet light.
4. The increased ultraviolet radiation may lead to faster deterioration of plants, fabrics, plastics and other materials.

Effects of Global Warming : Global warming can cause changes in rainfall patterns leading to flooding in some areas and drought in others. Monsoon flooding is expected to cause great loss of life in India, Bangladesh and South-East Asian countries. Over the last 100 years, because of Global Warming, the ice reserves have melted and the sea level has risen by about 10 to 25 cm. If this trend continues, areas will be submerged under sea water.

Question 4.
Define the following

(a) Ozone hole
(b) Tropopause
(c) Global warming
(d) Greenhouse effect
(e) Stratosphere
(f) Troposphere
(g) CFC’s
(h) Mesosphere
(i) Exosphere
(j) Thermosphere

Answer:

(a) Ozone hole : The large depletion of ozone layer in certain parts of the atmosphere is called Ozone hole.
(b) Tropopause : The upper limit of the troposphere is called Tropopause.
(c) Global warming : Gradual rise in Earth’s average temperature is called Global Warming.
(d) Greenhouse effect : The warming up of the atmosphere due to trapping of the solar radiation reflected by the earth by gases like carbon dioxide is called Greenhouse effect.
(e) Stratosphere : The layer of the atmosphere above the troposphere is called Stratosphere.
(f) Troposphere : The atmospheric layer closest to the earth is called Troposphere.
(g) CFC’s : These are chloro-fluoro carbons and are used as propellants in aerosol cans, refrigerants in refrigerators, air conditioning and as solvent cleaners in the microelectronic industry.
(h) Mesosphere : The layer of th® atmosphere which extends to a height of 80 km above the stratosphere is called Mesosphere.
(i) Exosphere : The topmost layer of the atmosphere is called the Exosphere.
(j) Thermosphere : Ionosphere, which extends from 80 km to 480 km is known as the Thermosphere.

Question 5.
What is Atmospheric pressure ?
OR
Is Atmospheric pressure the same on every place on the surface of the Earth ?
Answer:
Air has weight and, therefore, the atmosphere exerts pressure on the surface of the earth. It has been calculated that at sea level the pressure of air is about 1kg per square centimetre or enough to support a column of mercury 76 cm. in a tube. But with increase of height above sea level the pressure decreases because the overlying column of air goes on getting shorter.

Question 6.
Why does the atmosphere thin out at higher levels ?
Answer:
The atmosphere is held by the gravitational force of the Earth and is densest near the Earth’s surface where gravity is maximum. There are concentric layers of air in the atmosphere. Each layer has a different density. The upper layers are continually pressing down on the lower ones. Therefore, the air of the lower layer is always much heavier or denser, while the upper layers are thinner or less dense. Thus atmosphere thins out at higher levels and about 90 per cent of the mass of air lies within a height of about 20 km. from the surface of the earth.

Question 7.
What are the properties of Troposphere and Ionosphere?
Answer:
Properties of Troposphere :

1. It extends to a height of 18 km at the equator and declines gradually to a height of 8 km at the poles.
2. Most of the weather phenomena take place in this layer.
3. It contains almost all the water vapour and most of the dust particles. It is a turbulent zone.
4. The upper limit of troposphere is called tropopause.
5. In the troposphere, the temperature of air decreases at an average rate of 1°C for every 166 metres.

Properties of Ionosphere :

1. It extends from 80 km to 480 km.
2. It contains electrically charged gas molecules which reflect the radio waves used in long distance communication back to the earth.
3. The northern lights or aurora borealis are in this zone,
4. The temperature in this layer rises to a very high degree because the molecules in this layer absorb X-rays and ultra violet radiation coming from the sun.

Question 8.
Give reasons for the following :

1. The Earth does not experience extremes of temperature as in other planets.
2. The amount of water vapour in the atmosphere varies from place to place.
3. Solid particles play an important role in the atmosphere.
4. In the troposphere, the temperature decreases with height.
5. The stratosphere is crucial to life on Earth.
6. The ionosphere (thermosphere) is suited to long distance communication.
7. As a jet plane flies high in the sky, it leaves a white trail behind.
8. The exosphere allows the gas molecules to easily escape into space.
9. Dust particles plays a significant role in the atmosphere.

Answer:

1. The earth does not experience extremes of temperature as on other planets due to the presence of the atmosphere.
2. The amount of water vapour in the atmosphere varies from place to place due to difference in temperature.
3. The solid particles play an important role in the atmosphere because they act as nuclei for the condensation of water vapour around them.
4. The troposphere lies closest to the Earth’s surface and contains all the water vapour, mostly dust particles and clouds. This layer is subjected to intense mixing due to both horizontal and vertical circulation. Thus, the temperature decreases with height in this layer.
5. The stratosphere is crucial to life on the earth because the ozone layer present in it absorbs the harmful ultraviolet radiation of the sun.
6. The ionosphere is suited to long distance communication because radio waves used for this purpose are reflected back to the earth by the electrically charged gas molecules in it.
7. As a jet plane flies high in the sky, it leaves a white trail behind because moisture from the engine forms condensation tracks which are not disturbed due to lack of air movement at that height.
8. The exosphere allows the gas molecules to easily escape into space due to lack of gravity.
9. Solid dust particles present in the atmosphere act as a nuclei for change of water vapour into raindrops around them.They also scatter Sun’s radiation during Sunrise or Sunset, However, dust particles present in the lower layer of atmosphere may be harmful to us. They are the greatest health hazards.

Question 9.
‘Atmosphere is the most dynamic element in Environment’. Discuss.
Answer:
Atmosphere keeps on changing day and night. So the weather changes day-to-day. Great contrasts are found in day and night temperatures. Clouds change wind velocity.

Question 10.
‘The atmosphere acts as a blanket or a glasshouse’. Discuss.
Answer:
Atmosphere acts like a blanket keeping the earth warm. It absorbs incoming solar radiation and does not allow radiation to escape. So equable temperatures are found.

ICSE Solutions for Class 9 Geography – Hydrosphere

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions

Question 1.
Name the three ways in which movement of ocean water takes place.
Answer:
Oceanic water movement is affected by the rotation of the earth e.g. earth’s movement from west to east compels water to move from east to west as North and South equatorial current along with a contour equatorial current. Secondly, the direction of planetary winds motivates currents as the trade winds push forcefully towards polewards and afterwards by the Westerlies towards North East as warm currents touching North American eastern and European Western coast. Thirdly, the level of salinity makes the water to move less saline water to move saline water.

Question 2.
What are tides ? Name one factor that causes tides.
Answer:
Tides are the rise and fall of sea water due to gravitational forces of the sun and the moon. Tides are mainly caused by the centrifugal and centripetal forces of the earth and the moon.

Question 3.
What is the time interval between tides ? Name the factors responsible for this time interval ?
Answer:
On account of the continuous rotation of the earth and revolution of the moon around the earth, whenever the moon comes in the front of the earth, tide takes place at an interval of 24 hours and 52 minutes and at the same time on the opposite side of the earth the interval is of 12 hours and 26 minutes.

Question 4.
What are Spring and Neap tides ?
Answer:
When the gravitational forces of the sun and the moon work together to attract the earth due to being in a straight line, high tides or Spring tides are caused. When the sun and the moon are in right angle with respect to the earth, Neap tides or low tides are caused.

Question 5.
Name two types of ocean currents based on their temperature.
Answer:
There are two types of ocean currents e.g., warm and cold currents. The current which flows from warm tropical region to cooler temperate and polar region is called warm current and the current flowing from polar areas towards temperate and equational regions is called cold current, e.g. Gulf stream is a warm current and Labrador current is called cold current.

Question 6.
For what is the Gulf Stream famous?
Answer:
The Gulf Stream is a powerful warm ocean current affecting the climate of eastern coast of North America and western coast of Europe and it is an important source of tidal energy.

Question 7.
What happens when warm and cold currents meet ?
Answer:
By meeting the warm and cold currents, large amount of fog is created, which controls the temperature conditions in the fishing regions of the meeting grounds.

Question 8.
What is meant by ‘salinity’ of ocean water ?
Answer:
Salinity is the amount of sodium in the oceanic water. It is 35%.

Question 9.
Name the factors responsible for subsurface movement of ocean waters.
Answer:
The factors responsible for ocean currents are the rotation of the earth, difference in salinity, temperature and the prevailing winds.

Question 10.
State the relationship between temperature and density of ocean water.
Answer:
High temperature near the equatorial belt and landlocked seas leads to higher salinity or higher density of ocean water.

Question 11.
State one difference between waves and tides.
Answer:
Waves are the oscillatory (to and fro) movements in the oceanic water, but tides are particular turbulent motion of the oceanic water due to gravitational forces (centrifugal and centripital) working together with the earth and the moon which makes the waves of the ocean jumping upto several metres resulting in a typical phenomenon of violent waves i.e. tides.

Question 12.
How do evaporation and precipitation cause movement of ocean water.
Answer:
High amount of evaporation increases salinity of oceapic water and excess of precipitation makes water less saline. So the heavy saline water sinks down and the lighter water flows towards it to take its place as ocean current.

Question 13.
How is the rotation of the earth responsible for influencing the direction of currents ?
Answer:
The earth rotates from west to east. So, according to the first Law of Motion, the ocean currents start to flow from east to west as opposite direction, e.g. the North and South Equatorial currents flow from east to west.

Question 14.
Name the factors originating within the sea which cause ocean currents.
Answer:
The amount of salinity in the oceans in different parts is quite different. So the more saline water start to sink downwards and the less saline water runs to take its place on the surface, e.g., the ocean current flows from Atlantic ocean towards the Mediterranean sea.

II. Give reasons for the following

Question 1.
There are two high and two low tides in a day.
Answer:
The rotation of the Earth results in every meridian coming into the position of two high tides and two low tides very nearly every 24 hours.

Question 2.
Each day a tide is delayed by 26 minutes.
Answer:
Each day a tide is delayed by 26 minutes because the moon also rotates on its axis (west to east) while revolving round the earth. Since the earth rotates from west to east, the tide centre shifts westward. When the tide centre completes one round, the moon’s position is ahead of the tide centre by that time. The moon also revolves round the earth, with the result, the tide centre takes another 52 minutes to come under the moon. Thus, a particular tide centre takes 24 hours 52 minutes to come under the moon but by that time there is another tide at the opposite side of the referred tide centre and this happens after 12 hours 26 minutes.

Question 3.
Warm currents produce a milder climate.
Answer:
Warm currents of Gulf Stream has made the climate of eastern North America and Western Europe mild and pleasant for ideal industrial life and developed oceanic routes for trade. In the same way warm Kurosio current has made Japan a progressive country by leading in fishing occupation supporting the economy of Japan, Apart from this violent storms also follow the meeting places of warm and cold currents, e.g., Hurricanes in America and typhoons in China and Japan.

Question 4.
The eastern coasts of USA are comparatively cold.
Answer:
Due to the cooling effect of Labrador current keeps these coasts comparatively cold.

Question 5.
The waters of the Oyashio Current form the richest fishing grounds in the world.
Answer:
Due to meeting with warm Kurosio current creates large amount of fog regulating the ideal temperature for fish and the remarkable efforts of Japanese for fishing occupation makes this region the leading fishing grounds of the world.

Question 6.
There is heavy rainfall in Queensland but the Atacama desert is arid.
Answer:
Queensland’s coast is touched by the warm east Australian current and gets heavy rainfall by trade winds from sea towards land, but Atacama desert is touched by cold Peruvian current and the westerlies blowing from land towards sea make Atacama the cold driest desert in the world.

Question 7.
The coasts of Norway are not frozen in winter whereas its adjoining coasts are frozen for most parts of the year.
Answer:
The Western coast of Norway are not frozen in winter due to the warm effect of Gulf Stream or the North Atlantic Drift touching the coast.

Question 8.
Rich fishing grounds are located on the Pacific coast of North America.
Answer:
The Pacific coast of North America affected by the warm Kurosio current are the famous fishing grounds of salmon fish mainly shared by Canada.

III. Long Answer Questions

PQ. Differentiate between the three movements of ocean water-waves, tides and currents.
Answer:
Waves are oscillatory movement in water, manifested by an alternate rise and fall of the sea surface. Every wave has a wavelength, velocity, height and wave period. The rise and fall of sea water due to gravitational forces of the sun and the moon are called tides. The sea waves produced by tides are called tidal waves. Ocean currents are large masses of surface water that circulate in regular patterns around the ocean. It is of two types warm and the cold.

Question 1.
Discuss the origin of tides. Illustrate the formation of Spring Tides.
Answer:
The tides have their origin in the gravitational forces of the sun and the moon. The earth rotates from west to east and revolves round the sun following an elliptical orbit. Similarly, the moon, rotates from west to east and revolves round the earth along an elliptical orbit.
Spring Tides : Very high tides are caused when the sun and the moon and the earth are almost in the same line. Such high tides are called Spring Tides. The gravitational forces of the sun and the moon work together with combined force and thus a high tide is caused. The height of such Spring Tides is 20 per cent more than that of the normal tides. Such tides take place twice every month (during the full moon and the new moon) and their timing is fixed.

Question 2.
Differentiate between High Tides and Low Tides.
Answer:
High Tides :

1. When the sun and the earth and the moon are in the same line.
2. Caused when all the gravitational forces work together.
3. Occurs at the time of Full moon and new moon.

Low Tides :

1. When the sun and the earth and the moon are at the position of right angles.
2. Caused when the gravitational forces of the sun work against each other.
3. Occurs during the 8th day of each fortnight of a month.

Question 3.
Describing the types of ocean currents, state and factors responsible for causing the currents.
Answer:
Ocean currents are warm and cold according to the temperature. Ocean currents are caused by the rotation of the earth, force of prevailing winds, amount of salinity and the presence of the continental ejections etc.

Question 4.
Describe the circulation pattern of the following three ocean currents.

(a) Labrador Current of the Atlantic Ocean.
(b) The Kuroshio current
(c) Oyashio Current of the Pacific Ocean.
(d) The North Atlantic Drift.

Answer:

(a) Labrador Current originates from the Arctic ocean along the coast of Labrador and passes touching Newfoundland continuing southwards along the coast of Nova Scotia. It is joined by West Greenland and Baffin Island Current. It meets the warm Gulf Stream Current at the Grand Banks, making this region the famous fishing bank.
(b) The Kuroshio current – is a strong western boundary current in the western north Pacific Ocean. It begins off the east coast of Taiwan and flows north-eastward past Japan, where it merges with the easterly drift of the North Pacific Current. It is analogous to the Gulf Stream in the Atlantic Ocean, transporting warm, tropical water northward towards the polar region. It is also sometimes known as the Black Stream — the English translation of Kuroshio, and an allusion to the deep blue of its water — and also as the Japan Current.
(c) Oyashio Current is a cold current colliding with warm Kuroshio current along the eastern coast of Japan. It originates in the Arctic ocean and passes through the Bering strait proceeding towards south.
(d) The North Atlantic Drift : It is the eastern extension of Gulf Stream to Europe as a warm current.

Question 5.
Trace the origin and flow of the Gulf Stream. What is the effect of this current on the coasts of North America and Western Europe ?
Answer:
Gulf Stream – The Gulf Stream is one of the largest warm currents. It originates from the Gulf of Mexico (about 20°N) and moves in a north-easterly direction along the eastern coast of North America. The average speed is about 33 km per day and its average width is -about 70 km. Under the impact of the Westerlies, this warm current reaches the western coast of Europe (about 70°N latitude). The general direction of flow of the Gulf Stream, north of 30° N latitude, is northward. Near Newfoundland, its water mixes with the cold water of the Labrador Current, which forms very dense fog. The foggy conditions around Newfoundland hamper the navigation of ships. From here, the Gulf Stream moves north eastwards. This current gradually widens and its speed decreases. It becomes a prominent, slow-moving current known as the North Atlantic Driff. Near western Europe, it splits into two parts. One part moves northwards, past UK and Norway, while the other part is deflected southwards as the cold Canary Current. The warm water of the Gulf Stream modifies the weather conditions off the eastern coast of North America and the western coast of Europe.

Question 6.
Describe four major effects of currents.
Answer:
Major effects of currents are visualised by the distinct effect of the Worm Gulf Stream on the climate of eastern. North . American region and the western region of Europe and the oceanic trade routes joining the most industrialised regions of the world. On the other hand cold current of Benguela keeps the South African Western Coast mild and cool. Kurosio warm current keeps the eastern coast of Japan ideal for fishing.

ICSE Solutions for Class 9 Geography – Denudation

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions

Question 1.
What do you mean by denudation ?
Answer:
Denudation is the wearing away of landmass by various processes like weathering, erosion mass movement and transportation. It results in lowering the level of land, rounding exposed rock surfaces and levelling the peaks.

Question 2.
Name important factors which affect work of a river.
Answer:
Refer Long Answers Question 1

Question 3.
What is the main function of a river in its upper course in land formation ?
Answer:
In the upper course the dominant activity of a river is erosion. Many land forms are shaped by this activity of the river. Along its course, it erodes bed and banks, and carries large boulders of rock with it. Under the impact of rush of water.

Question 4.
Name two important land forms of river erosion.
Answer:

The two landforms resulting from erosion in the upper course of a river are the following :

1. V-shaped Valleys : It is formed from a stream eroding downward, through a process, called down cutting. These valleys are formed in the initial stages of rivers and have steep slopes.
2. I-shaped Valley : In regions of hard rocks it develops almost vertically in an I-shape. River valleys are normally formed in areas of sufficient rainfall and where rocks are not very hard or resistant.

Question 5.
How is a waterfall formed ?
Answer:
Waterfall : A waterfall is generally formed due to large differences in the rate of erosion. The smaller differences lead to formation of step-like features known as rapids. The water that falls down the edge of a hard resistant rock may have at the bottom a soft rock. It is this soft rock that gets eroded fast and creates a hollow basin called plunge pool. Some of the world’s highest and best known falls are Angel Falls (986 m) in Venezuela and Yosemite fall (778 m), California, USA.

Question 6.
State the main function of a river in its middle course.
Answer:
At this stage, the gradient is reduced, and the river flows more slowly. The middle course of the river begins when it leaves the mountains area and enters the plains. In the middle course the energy required to transport the materials is just enough to drag large particles. Fine particles remain suspended in water, large particles are just dragged along the bed of the river and smaller ones are rolled down in the centre. The river also gets windened as a result of great volume of water and the impact of the load.

Question 7.
How are meanders formed ?
Answer:
River meanders are bends of longitudinal courses. S-shaped meanders which are common to most rivers result when a ^ channel-forms a curved path. These are the result of both erosion and deposition work of rivers.
Meanders generally form under conditions of a gentle slope and sufficient water in rivers. The river flow is diverted by an obstruction allowing the river to do lateral erosion work.

Question 8.
Name two landforms in the lower course of a river.
Answer:

1. Delta : The river divides itself into many distributaries.
   These distributaries are also subdivided into mini-distributaries. This is due to depsoition of sediments over a large’area near the mouth of rivers. Such sedimentation occurs on the sides of the stream, at the mouth, in the front part as well as in the bed of the river. The deposition over a large area results in a triangular-shaped formation called delta. It resembles the Greek letter A The Ganga-Brahmaputra delta is growing towards the sea. It is also one of the largest in the world.
2. Oxbow lakes are also formed in the lower course of a river.

Question 9.
Where is wind erosion most predominant ?
Answer:
The wind erosion is most predominant in arid regions. Since there is little vegetation or moisture to bind the loose surface materials, the effects of wind erosion are more pronounced in the desert region.

Question 10.
What are known as Deflation Hollows ?
Answer:
Deflation Hollows : Deflation involves the lifting as well as the blowing away of loose materials from the ground. The sands and pebbles are carried in the air or driven along the ground. The finer dust and sands may be deposited even outside the desert margins. Deflation results in the lowering of the land surface to create depressions called deflation hollows.

Question 11.
Name one chief landform of wind deposition ?
Answer:
Hamada is the hard bedrock exposed after sweeping away of the dust and sand by the wind.

Question 12.
Name two chief types of sand dunes.
Answer:
The following two types of sand dunes are seen

1. Barchan : These are moon-shaped dunes. They are live dunes which advance steadily before winds that blow from a particular direction. They are found in the deserts of the Sahara. These are initially formed by an accumulation of sand at an obstacle, such as a heap of rocks. These occurs transversely to the wind, so that their horns thin out and become lower in the direction of the wind.
2. Longitudinal Dunes or Seifs : These are long and narrow sand-ridges which grow parallel to the direction of the prevailing wind. They are found in the interior parts of deserts. In the Libyan desert, they are known as Seifs (means ‘sword’ in Arabic). In the Thar Desert they are confined to the western margin, where the force of south-west monsoon influences their formation. An important feature of such a dune is that in its crest line there are rise and fall patterns. Seifs are found in the Sahara, Iran, Thar Desert (India) and West Australia. These sand dunes are stationary and they remain in a fixed position.

Question 13.
State three chief characteristics of barchans.
Answer:

1. Barchans are moon-shaped dunes. They are live dunes which advance steadily before winds that blow from a particular direction.
2. They occurs transversely to the wind, so that their horns thin out and become lower in the direction of the wind.
3. The windward side is convex and gently-sloping while the leeward side (being sheltered) is concave and steep.

II. Long Answer Questions

Question 1.
Briefly describe the factors which affect the work of a river.
Answer:
Various factors affect erosion, transportation and deposition work of a river. Important factors include the following :

1. Velocity of water : Erosion and transportation are both maximum when velocity is high. Deposition, on the other hand takes place when velocity of water is low.
2. Volume of water : The larger the volume of water, the greater is the power of erosion and transportation. Deposition, on the other hand, takes place better when there is reduced volume of water as well as when the load is greater.
3. Load : Load is the material transported by a river. The load of a river, does all the work of erosion and deposition. Mass wasting, deepening of river valleys and formation of landforms depend on the load a river carries.

Question 2.
Describe chief landforms of river deposition.
Answer:

The cheif landforms resulting from the deposition of a river are the following :

1. V-shaped Valleys : It is formed from a stream eroding downward, through a process, called down cutting. These valleys are formed in the initial stages of rivers and have steep slopes.
2. I-shaped Valley : In regions of hard rocks it develops almost vertically in an I-shape. River valleys are normally formed in areas of sufficient rainfall and where rocks are not very hard or resistant.

Question 3.
Write a short note on the three stages of a river.
Answer:
From the source to its mouth, a river is divided into three main sections – Upper Course, Middle Course and Lower Course. These three sections are also called the Profile of a River.

• Upper Course – In the upper course the dominant activity of a river is erosion. Many land forms are shaped by this activity of the river. Along its course, it erodes bed and banks, and carries large boulders of rock with it. Under the impact of rush of water.
• Middle Course – At this stage, the gradient is reduced, and the river flows more slowly. The middle course of the river begins when it leaves the mountains area and enters the plains. In the middle course the energy required to transport the materials is just enough to drag large particles. Fine particles remain suspended in water, large particles are just dragged along the bed of the river and smaller ones are rolled down in the centre. The river also gets windened as a result of great volume of water and the impact of the load.
• Lower Course – The river divides itself into many distributaries. These distributaries are also subdivided into mini-distributaries. This is due to depsoition of sediments over a large area near the mouth of rivers. Such sedimentation occurs on the sides of the stream, at the mouth, in the front part as well as in the bed of the river. The deposition over a large area results in a triangular-shaped formation called delta. It resembles the Greek letter A The Ganga -Brahmaputra delta is growing towards the sea. It is also one of the largest in the world. Oxbow lakes are also formed in the lower course of a river.

Question 4.
Describe the work of wind erosion and state two important landforms of wind erosion.
Answer:
Winds move along the desert floors with great speed and the obstructions in their path create turbulence. Storm winds are formed which are very destructive. Winds cause deflation, abrasion and impact. Deflation includes lifting and removal of dust and smaller particles from the surface of the rocks. The impact is the simply the shear force of momentum which occurs when sand is blown into or against a rock surface. These are the ways in which wind action creates a number of interesting erosional and depositional features in the deserts.
Winds are not the only agent responsible for the erosional features of the deserts. Along with winds the running water is also important for this.

ICSE Solutions for Class 9 Geography – Weathering

ICSE SolutionsSelina ICSE SolutionsML Aggarwal Solutions

Exercises

I. Short Answer Questions.

Question 1.
What is weathering ?
Answer:
Weathering involves disintegration or decay of solid rock due to change in temperature and weather and their impact on the composition of rock.

Question 2.
Give one point of difference between physical and chemical weathering.
Answer:
Physical weathering does disintegration of rock without chemical reaction and the chemical weathering does change in chemical compounds within rock.

Question 3.
What is known as exfoliation ? Name the processes involved in it ?
Answer:
Sudden change in temperature causes fissures in the rocks through which water penetrates to motivate chemical weathering along with sudden contraction and expansion due to change in temperature peels out the upper layer of rock known as exfoliation.

Question 4.
Name the four processes involved in chemical weathering.
Answer:
These are solution, carbonation, oxidation and hydration.

Question 5.
What is known as oxidation ?
Answer:
It is the process of reaction of minerals present in rocks to atmospheric oxygen.

Question 6.
Briefly describe biological weathering.
Answer:
Biological weathering is done by animals, insects plants and man, because these break up the rocks through making holes, root channels and construction of building, canals etc.

Question 7.
What are exogenic forces ?
Answer:
These are the external forces that sculpture the surface features of the land.

Question 8.
What is called denudation ? Name the processes involved in it.
Answer:
Denudation is the wearing away of landmass by various agents as water, wind and ice through various processes like weathering, mass movement, erosion and transportation.

Question 9.
Name the two processes of gradation.
Answer:
Two processes are denudation and aggradation.

Question 10.
What is the chief characteristic of weathering in tropical climates ?
Answer:
Tropical climates are noted for distinct dry and wet season and high rate of evaporation. During rainy season the oxides of iron and aluminium are dissolved in water and mix up with the soil to form laterite soils.

Question 11.
What is known as mass wasting ?
Answer:
The movement of loose material derived from the bed rock through weathering is called mass wasting.

Question 12.
Name any two slow movements of mass wasting.
Answer:
Slow movements of mass wasting an be divided into two
main types — Creep and Solifluction.
Creep : The slow downhill movement of debris is called soil creep.
Solifluction : The water mixed with soil forms clay which moves as a thick viscous fluid.

Question 13.
Give one example of rapid mass movement.
Answer:
Rapid mass movement includes large amount of debris, soil, boulders and rock pieces etc, e.g. landslides and sheet erosion or displacement of the upper rock strata in large amount to uncover the rocks lying below.

Question 14.
What is known as Sheet Wash ?
Answer:
It is the rapid movement of rock debris etc in heavy amount taking the form of a thick sheet of thick fluid of soil and clay removing settlement and vegetation cover, too.

II. Give a technical term for each of the following :

Question 1.
Disintegration or decomposition of rock.
Answer:
Weathering.

Question 2.
Peeling off of the outer layer of rock through contraction and expansion.
Answer:
Exfoliation

Question 3.
Expansion of minerals in rocks on coming into contact with rainwater.
Answer:
Hydration.

Question 4.
The leveling of land surface by erosion and deposition.
Answer:
Gradation.

Question 5.
The process in which a landform of lower level is upgraded to a higher level.
Answer:
Aggradation.

III. Say whether the following are ‘True’ or ‘False’.

1. Temperature is not a factor in physical weathering.
Answer. False

2. In dry climates mechanical weathering is dominant.
Answer. True

3. In Polar regions there is no chemical weathering.
Answer. True

4. External forces are engaged only in erosion.
Answer. False

5. Shear plane is the surface on which movement of a landslide takes place as a result of its breaking off.
Answer.True

IV. Long Answer Questions.

PQ. Describe the process of denudation and gradation.
Answer:
Denudation is the process of wearing away of rock-strata by water, wind and ice along with change in weather and temperature.
Gradation is the process of leveling down the whole landform gradually to ground level by various agents of change mainly water, (rivers), wind and ice (glaciers), etc.

Question 1.
Define weathering and describe the chief characteristics of weathering.
Answer:
Weathering is the process of breaking down of rocks but not its removal. It is described as disintegration or decomposition of a rock in size by natural agents at or near the surface of the earth.
Chief characteristics of weathering are disintegration of rocks, chemical change in rocks, change in the surface of land, formation of soil, several processes involved in weathering like temperature and weather change and reactions, transportation of rock material from one place to another resulting in formation of large plains like Northern plain of India.

Question 2.
Distinguish between physical and chemical weathering.
Answer:
Physical Weathering :

1. Rock disintegration without any change in chemical constituents of rocks takes place.
2. Factors such as temperature, moisture, pressure cause physical break-up of rocks.
3. It takes place in hot dry and cold areas due to rapid temperature changes.
4. Rocks are affected to great depths.
5. Its agents are temp erature and moisture.

Chemical Weathering :

1. Mineral in rocks are dissolved or altered.
2. Temperature, moisture, etc., cause minerals in rocks to dissolve in water or convert them into other minerals.
3. It takes place in hot and humid areas due to chemical action of minerals in rocks.
4. It mostly takes place near the surface of the earth.
5. Its agents are solution, oxidation, carbonation and hydration.

Question 3.
Describe chemical weathering mentioning the processes involved in it.
Answer:
Chemical weathering takes place with the help of agents as water, wind and various organic acids, reacting in the chemical composition of rocks which are then disintegrated. Four main processes are solution by dissolving salts in the rocks with water, carbonation works with the reaction of carbon dioxide with rocks, oxidation takes place through atmospheric oxygen reacting with minerals present in rocks, hydration is evident by mixing of rainwater with minerals in rocks, which expand by this and become heavy.

Question 4.
What is biological weathering ? State the main agents of biological weathering.
Answer:
Biological weathering is weathering caused by plants and animals. Plants and animals release acid forming chemicals that cause weathering and also contribute to the breaking down of rocks and landforms. It is also known as Organic weathering. Its main agents are animals, insects, plants and man. In all the cases, however, both physical disintegration and / or chemical decomposition are involved. Their role can be explained as follows :

1. Animals and Insects : Animals like rabbits, worms, moles and insects bring large quantities of fine material to the surface. Burrowing animals help to loosen the surface materials around the rocks facilitating their physical disintegration. Upon death, the decaying physical also provide many chemicals and acids for rock disintegration.
2. Vegetation : Roots of large trees reach deep into rocks and cause physical disintegration due to pressure. Most of : vegetation, however, prevents disintegration of rocks because it binds the surface layer and does not allow exposure of rocks beneath to the elements of weathering.

Question 5.
Describe the chief characteristics of weathering in different climates.
Answer:
Equatorial region is noted for more active chemical weathering due to excess of temperature and water ; tropical region is remarkable for formation of laterite soil by mixing of oxides of iron and aluminium in the soil due to change in heating and much evaporation.

Question 6.
State and explain the classification of mass movements.
Answer:
Mass movements are divided into slow and rapid movements. Slow movement includes Creep, movement of soil and debris and Solifluction or clay formation Rapid movement includes landslide, Earth Flow or heavy thick paste of soil down the slope, Mud Flow in the areas without vegetation cover and Sheet Wash in the form of large sheet flow snatching a thick rock strata uncovering the rocks below. It may also take place by human activities of settlement.
Mass movement has built many remarkable landforms as Himalayan lakes, Terraces, escarpment etc.

Practice Questions (Solved)

Question 1.
Name two processes involved in denudation.
Answer:
Weathering and Erosion.

Question 2.
What does the term denude mean ?
Answer:
To lay the rocks bare.

Question 3.
What is weathering ?
Answer:
Breaking up of rocks by agents related to atmosphere.

Question 4.
Name the gases involved in the process of chemical weathering.
Answer:
Weak acids, oxygen, carbon dioxide, hydrogen.

Question 5.
In which region underground water is an effective agent of denudation.
Answer:
Underground water is an effective agent of denudation in limestone regions.

Question 6.
Name few well known physical features caused by chemical weathering.
Answer:

1. Limestone and chalk landforms of Karst region of Yugoslavia.
2. Weathering of granite rocks in Malaysia.

Question 7.
Why is mechanical weathering also known as physical weathering ?
Answer:
Because it involves physical disintegration of rocks. Physical disintegration is quickest when rock is already weakened by chemical weathering. So it is primarily known as mechanical weathering.

Question 8.
What is weathering ? Illustrate the process graphically.
Answer:
The break-down but not removal of rocks is called weathering. It is a process of wearing away of land through forces of nature like weather, running water, ocean currents etc. Weathering is a single process and takes place in air.

Question 9.
Distinguish between :

1. Weathering and Denudation
2. Loess and Alluvium.

Answer:

1. Weathering and Denudation : Weathering is a process 4 of gradual disintegration of rocks by atmospheric or weather forces. Denudation is a process of wearing away of land and it includes weathering also.
2. Loess and Alluvium : Alluvial soils are formed by depositional activity of running water and loess by wind. Alluvium contains high mineral and humus content, and loess is highly permeable.

Question 10.
On what factors does the weathering depend ?
Answer:
Weathering depends upon :

• structure of rocks
• climate
• vegetation
• topography and slope of land.

Question 11.
What do you understand by Denudation ?
Answer:
Denudation is a general term which covers all the agents causing destruction or the wearing away of the rock surface of the earth together with their transportation and final deposition.

Question 12.
Name any two agents of denudation.
Answer:

1. The weather in which the chief agents are heat and cold which did water and frost
2. The running water

Question 13.
Name the gases which help in chemical weathering.
Answer:
The following atmospheric gases help in the process of chemical weathering:

1. Oxygen
2. Hydrogen
3. Carbon dioxide

Question 14.
What is humus ? How is it formed ? What is its significance in soil formation ?
Answer:
Humus : Humus is a dark substance formed in soils. It is a dead organic matter formed by decay of animals and plants. Trees, shrubs, grass and bacteria help in the formation of humus. In warmer climates, humus is destroyed by countless bacteria. In colder areas soils are rich in humus and it is collected in the soil. Tropical humid soils are poor in humus because it is consumed by bacteria.
Humus is vital to the fertility of soils. It provides nitrogen, phosphorus and calcium to the soils. It sustains other forms of life. It helps the weathering of minerals to add to fertility of soils. It increases water holding capacity of soils.

Question 15.
What is a badland topography ?
Answer:
A highly dissected land surface is known as badland. In sloping areas, gully erosion results in soil erosion. These gullies develop a ravine land a badland topography. This topography consists of ridges, earth pillars, ravines, escarpments, etc. This topography is found in Chambal Valley of Madhya Pradesh in India.

Question 16.
Explain the processes of physical weathering giving examples.
Answer:
The disintegration of the bedrock due to changes in temperature and freezing action of water by mechanical process is called physical weathering e.g. frost or snow lying between the cracks forces to expand the rocks cracks which helps in disintegration. Besides this, the change in temperature does the expansion and contraction of rocks resulting in breaking the rocks into smaller pieces.

Question 17.
Distinguish between the following

(a) ‘Weathering’ and denudation.
(b) ‘Mechanical Weathering’ and ‘Chemical Weathering’.
(c) Sheet erosion and gully erosion.

Answer:
(a) Weathering :

• Weathering is the physical and chemical weathering of rocks due to mechanical and chemical action of water, wind and ice.

Denudation :

• Denudation includes both weathering and erosional proceses by which the natural agents of change (water, wind and ice), continously try to change the face of the earth.

(b) Mechanical Weathering :

• It is done by the change in temperature and action of ice which breaks the rocks into small pieces.

Chemical Weathering :

• It is done by oxidation hydration, carbonation and solution etc chemical processes which causes the breaking of rocks.

(c) Sheet Erosion :

• Sheet Erosion causes washing out the upper layer of soil and vegetation cover due to heavy rainfall or floods.

Gully Erosion :

• Through gully erosion deep cuts, cracks and trenches are carved in the soil-bed, These tend to be deeper channels known as ‘gullies’.

Question 18.
What do you understand by the following terms :

(a) Exfoliation
(b) Regolith
(c) Oxidation
(d) Carbonation
(e) Desilication
(f) Humus

Answer:

(a) Exfoliation — It is the process of scaling off the curved outer shells of the rock. Exfoliated dome-shaped rocks are largely found in great deserts.
(b) Regolith — It is the loose material created by the weathering of rocks i.e. small pieces of rocks.
(c) Oxidation — Formation of oxygen compounds with the contact of air with rocks e.g. iron-oxide etc. is known as oxidation.
(d) Carbonation — Formation of carbon compounds with the contact of air with rocks e.g. Calcium Carbonate, which is easily carried on by ground water.
(e) Desilication — The solution of silica of the rocks with water is called desilication.
(f) Humus — It is the decayed vegetation material found in the soil.

Question 19.

(a) What are different types of soil according to their texture ?
(b) How are the different kinds of soils in Temperate zones formed ?

Answer:
(a) According to the texture (sizes of the soil particles), the soil is divided into three main types i.e. Clay, loam (silt) and sandy loam (sand gravel), the diameter of soil particles ranges from .0002 mm to more than 2 mm. Soil structure refers to the physical arrangement of the soil.
(b) The kinds of temperate zone soils may be classified as follows.
Name :

1. Podzol
2. Cheronozems region
3. Brown and Grey soils
4. Chestnut soils

Region :

1. Cool and cold coniferous forest
2. Grassy steppes and semi arid lands
3. Deciduous forest region of high and middle latitudes
4. Arid margins of steppes.

Question 20.
Rewrite the following sentences, choosing the right word from those given in brackets :
Answer:

• (Humus / Regolith) is produced by the decayed organic material, including dead leaves, stems roots, living bacteria, fungi, worms and other organisms.
• (Weathering / Denudation) refers to the gradual disintegration and decomposition of rocks which lie exposed to the elements of weather.
• (Young / Mature) soils are those which are undisturbed by erosion or deposition.
• (Hydration / Carbonation) occurs when the water itself combines chemically with some element or mineral.
• (Oxidation / Solution) is the chemical process in which some of the minerals are dissolved by the water.

Question 21.
Define the following terms briefly :

(a) Soil texture
(b) Soil structure
(c) Soil profile
(d) Soils
(e) Chernozems

Answer:

(a) Soil texture — It is the make up of the soil referring to the sizes of the soil particles.
(b) Soil structure — The structure of the soil may be blocky, granular, prismatic or columnar and platy which decides the movement of the soil water.
(c) Soil profile — The vertical structure of the soil from the bedrock below upto the surface soil is called the soil profile.
(d) Soils — The soils are the aggregate of loose, unconsolidated material along with micro-organism mineral compounds, humus etc.
(e) Chernozems — are the richest soils found in the grassy steppes and are best for wheat cultivation.

Question 22.
What are the various factors governing the formation of soil ? Which one is the most important and why ?
Answer:
The factors influencing the formation of soils are the parent rock, topography, vegetation, climate and time span. Out of these climate is the most important because it controls the type of weathering the first step of the soil formation process.

Question 23.
Match the following pairs correctly


Answer:

Question 24.
Explain the processes of physical weathering giving examples.
Answer:
Physical weathering : It is also called Mechanical weathering. It includes the breaking up of rocks without changing their composition. It means disintegration of rocks by mechanical means. This type of weathering results from the action of temperature changes, frost, wind and rainfall. It is important in dry areas.
The change in temperature causes the bare rocks to expand when warmed by the sun, and contract when night falls and their heat is lost by radiation. The mineral grains of a bed rock expand or contract at different rates as a result of heating or cooling. This causes the breaking of rock into fragment of grains.

Question 25.
Distinguish between the following :

(a) Weathering and Denudation
(b) Physical Weathering and Chemical Weathering.
(c) Sheet erosion and Gully erosion.
(d) Granular Disintegration and Block Disintegration.
(e) Solution and Hydration
(f) Erosion and Weathering.

Answer:

(a) Weathering : ‘Weathering’ means the disintegration and decay of the rocks cover of the earth’s surface. It is an action which affects rocks in the place where they are. The rate of weathering will depend on the climate of the region, on the kind of rock, on its chemical composition, on its hardness and structure which may allow water to penetrate easily into it.
Denudation : Denudation is a general term which covers all the agents causing destruction or the wearing away of the rock surface of the earth together with their transportation and final deposition.
(b) Physical weathering : It is also called Mechanical weathering. It includes the breaking up of rocks without changing their composition. It means disintegration of rocks by mechanical means. This type of weathering results from the action of temperature changes, frost, wind and rainfall. It is important in dry areas.
Chemical weathering : The decomposition of rocks by chemical processes is called chemical weathering. This type of weathering produces a chemical change in minerals of rocks. It results from the action of weak acids and atmospheric gases like oxygen, carbon dioxide, hydrogen. It involves the process of oxidation, carbonation, solution and hydration. It is important in hot humid areas.
(c) Sheet Erosion : When the vegetation cover of an area is removed, the rain, instead of sinking into ground, washes the soil down slope. Each succeeding rain-storm washes away a thin layer of absorbed top soil. This is known as Sheet Erosion.
Gully Erosion : When rain falls more heavily, the flow off storm water finds its way down hill in a series of channels.
Every fresh down pour widen and deepens the channels which develop into gullies. Gullies cut up agricultural land into small fragments and make them finally unfit for cultivation. This type of erosion is known as Gully Erosion.
(d) Granular Disintegration ; The temperature changes during summer and winter lead to expansion, due to heating and contraction, due to cooling. Different minerals present in the rocks may have different rates of expansion and contraction. For example dark coloured minerals will absorb more heat and expand to a greater extent than light coloured minerals. Such alternating expansion and contraction between day and night leads to a break up of the rock into different minerals. This type of weathering is called granular disintegration.
Block disintegration : A rock may split along joints or fissures by the repeated freezing of water in cracks or other openings, because water expands nearly one-tenth of its volume when it freezes. It is followed by melting during daytime repeatedly. This type of weathering is called block disintegration because the rock is split into rectangular block along the joints.
(e) Solution : It is the chemical process in which the soluble minerals are dissolved by water entering into rocks through crevices. The dissolved minerals are removed with the flow of water resulting in the break up of the rock. Rock-salt and gypsum weather away chemically because of this process. Since silica is highly soluble in water, and silica is found in so many rocks, this process is also known as Desilication.
Hydration : It is the process by which some minerals in crystalline form absorb water and become a powdery mass. Feldspar, a common rock forming crystalline mineral absorbs water and becomes a mass of clay by the process of hydration. The other minerals present along with feldspar get separated into loose particles and the rock breaks up.

(f) Erosion and Weathering :
Erosion :

1. Erosion includes the work of weathering away of rocks of the earth.
2. It involves motion.
3. River, glacier, wind are its main agents.

Weathering :

1. Weathering is the breaking of rocks by elements of atmosphere.
2. It involves no motion.
3. Temperature, frost, wind, plants and animals are its main agents.

Question 26.
What do you understand by the following terms :

(a) Exfoliation
(b) Regolith
(c) Oxidation
(d) Carbonation
(e) Weathering
(f) Humus
(g) Soil profile
(h) Landslide
(i) Soil texture
(j) Gradation
(k) Frost action

Answer:

(a) Exfoliation : When the rock consists of homogeneous minerals the thin surface layer of rock absorbs heat during the day and expands, while during the night, this surface layer contracts. In a few days the rock breaks up or peels off into layers. This type of weathering is called exfoliation.
(b) Regolith : The loose material which has resulted from the breaking down of bed rocks is called Regolith.
(c) Oxidation : The Atmospheric oxygen combines with minerals of rocks especially iron compounds to fonn oxides. The rocks begin to decay and crumble to a powdered mass of brown dust. This process is known as oxidation.
(d) Carbonation : The process of absorption of carbon dioxide from the atmosphere by minerals present in the rocks is called carbonation.
(e) Weathering : The disintegration or decay of rocks on the surface of the Earth due to atmospheric conditions is called weathering.
(f) Humus : The organic matter present in the soil is called humus.
(g) Soil profile : The vertical cross section of soil is called soil profile.
(h) Landslide : Sudden movement of weathered particles down the slope is known as landslide.
(i) Soil texture : Soil textures refers to size of the particles comprising the soil.
(j) Gradation : The process of erosion, transportation and deposition of rock material is called deposition.
(k) Frost action : The freezing of water in the cracks and openings of rocks during the night leading to the splitting up of the rocks is called frost action.

Question 27.
Account for the two types of weathering.
Answer:
Weathering may be :

1. Mechanical : weathering is the disintegration of rocks by mechanical forces, without chemical changes.
2. Chemical : weathering is the gradual decomposition of the rock owing to the reaction and combination of the constituent minerals of the rock with oxygen or carbon dioxide present in the atmosphere. In Chemical weathering the presence of water is essential.

Question 28.
Describe how changes of temperature lead to weathering.
OR
How do changing temperature lead to weathering ?
Answer:
The alternate action of heat and cold helps in weathering of rocks. For example, during the day, the rocks expand by heat and they contract due to cold during night. It tends to loosen the particles of rock and it begins to disintegrate because every rock is composed of different minerals, which are affected differently due to changes in temperature and therefore the component parts of the rock begin to lose cohesion.

Question 29.
How does frost action cause weathering ?
Answer:
In the middle latitudes, temperature may be above freezing point of water during day time and below freezing point during the night. Water present in the joints and fissures in the rocks, gets frozen into ice during the night. Freezing of water results in expansion in volume and the fissures widened.
It is followed by melting during day time repeatedly. It is called block disintegration because the rock is split into rectangular blocks along the joints. Frost action is most common in the tropical regions and in high mountains all the year round.

Question 30.
Name the different processes of chemical weathering.
Answer:
Different processes of chemical weathering are as follows :

1. Solution
2. Hydration
3. Oxidation
4. Carbonation

Question 31.
Describe the work of plants as agents of weathering.
Answer:
Plants protrude their roots through joints in the rocks and as the plant grows, the joints in the rocks get widened. The widening of joints allows water to seep through. Seepage of water may cause chemical weathering or frost action. Decay of plant remains like flowers, leaves, etc., result in the formation of organic acids which may react with minerals present in the rocks. The leads to chemical weathering.

Question 32.
Which human activities lead to weathering of rocks ?
Answer:
Following human activities lead to weathering of rocks :

1. Mining
2. Quarrying
3. Deforestation

When trees are cut the binding action of the roots of the trees is no longer present. Rocks get exposed to sun and rain and weathering takes place rapidly. Mining and quarrying exposes bare rocks on the surface and these get weathered quickly.

Question 33.
State the effects of weathering.
Answer:
Effects of weathering :

1. It causes landslides.
2. It causes mud flow, that is, the flow of weathered material, soggy with water, deacon a hillside or a slope.
3. Weathering breaks down the particles of rocks gradually and makes it easy for rivers and other agents of denudation to transport them down the slope. It exposes the rock to further weathering. Thus weather assists the agents of denudation.
4. Weathering assists the formation of soils.

Question 34.
Give reasons for the following :

1. Change of temperature leads to physical weathering.
2. Presence of water aids chemical weathering.
3. Human activities encourage weathering.
4. Climate is the most important factor of soil formation.
5. Farmers are encouraged to adopt soil conservation methods.
6. A soil dominated by clay makes tilling difficult.
7. Grassland soils are less acidic than forest soils.

Answer:

1. Change of temperature leads to physical weathering because it leads to expansion due to heating and contraction due to cooling.
2. Presence of water aids chemical weathering because it dissolves soluble minerals present in the rocks.
3. Human activities encourage weathering because these activities expose rocks to sun and rain due to which weathering takes place rapidly.
4. Climate is the most important factor of soil formation because it controls the type of weathering of the parent rock arid availability of soil moisture for plants and micro-organisms.
5. Farmers are encouraged to adopt soil conservation methods because it protects the top layer of the soil.
6. A soil dominated by clay makes tilling difficult because it is sticky and tough.
7. Grassland soils are less acidic than forest soils because grasses are heavy feeders on the bases.

Question 35.
Explain the following terms.

1. Colloids
2. Bases

Answer:

1. Colloids : Colloids are extremely tiny particles which are so small that they can not be seen by optical microscope ‘ and remain suspended indefinitely in water. They have the property of being electrically charged and can attract and hold ions of calcium, magnesium and potassium, known as bases. These bases are required by plants for their growth. – Soil colloids are also useful in holding water in the soil. When present in large quantities, they make the soil sticky and tough so that it is difficult to cultivate.
2. Bases : Ions of calcium, magnesium and potassium are known as bases. They are required by the plants for their growth.