geography Class 7 ICSE Solutions

ICSE Solutions for Class 7 Geography Voyage – Study of Weather

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 7 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 7 with Free PDF download option. Geography Voyage for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

ICSE Solutions Class 7 Geography History & CivicsMathsPhysicsChemistryBiology

VALUES AND LIFE SKILLS

Many people leave their pets in parked cars. They think they will be gone for a few minutes, or it will be alright to leave a window open. The temperature inside a parked car can rise up to more than 50°C in a matter of few minutes, irrespective of it being a hot or a cloudy day.
What would be the right thing to do if you see a pet locked inside a car on a hot day ?
Answer:
Leaving pets locked in cars is never safe. But when the weather gets warmer, it can be deadly. High temperatures can cause irreparable organ damage and even death. Protecting animals from an unnecessary death is a problem we can all agree to prevent.

EXERCISES

A. Write true or false. Correct the false statements.

1. A rise in temperature causes more condensation while a fall in temperature results in evaporation.
Answer. False.
Correct : Arise in temperature causes more evaporation while a fall in temperature results in condensation.

2. ‘4 o’clock showers’ are caused by cyclonic rainfall.
Answer. False.
Correct : ‘4 o’clock showers’ are caused by convection currents.

3. Heavy rainfall occurs on the leeward or rain shadow side of a highland.
Answer. False.
Correct : Little rainfall occurs on the leeward or rain shadow side of a highland.

4. The direction of wind blowing on the surface of the earth is affected by the Coriolis force.
Answer. True.

5. Cyclones and anticyclones are examples of variable winds.
Answer. True.

B. Fill in the blanks.

1. The temperature of a place depends upon its latitude, altitude, distance from the sea, ocean currents, winds, cloud cover and slope and aspect.
2. Pressure difference causes horizontal movement of air called wind and vertical movement of air called current.
3. Humidity refers to the amount of moisture or water vapour present in the air.
4. Planetary winds are also called permanent or prevailing winds.
5. The amount of cloud cover in the sky is expressed in discs (shaded in different proportions).

C. Answer the following questions in brief.

Question 1.
What are the elements that determine weather and climate?
Answer:
The elements that determine climate are the same as those weather, namely temperature, atmospheric pressure, humidity, precipitation, wind direction and speed, cloud cover, and sunshine.

Question 2.
Name the factors that determine the temperature at a place.
Answer:
The factors that affect the temperature of a place are latitude, altitude, distance from the sea, ocean currents, winds, cloud cover, and slope and aspect.

Question 3.
How do the following elements influence the weather of a place :

1. temperature
2. pressure?

Answer:

1. Temperature : When the temperature of a place increases, the air gets heated, expands and rises. This leads to a decrease in air pressure in the area. When the temperature falls, the air gets cold, contracts, and descends downwards. This leads to an increase in air pressure. Thus, air pressure decreases with an increase in temperature. This is the reason why areas close to the equator generally have low air pressure.
2. Pressure : Atmospheric pressure is the pressure that the atmopshere exerts on the surface of the earth because of its weight. There is a close relationship between pressure and temperature — high temperature means low pressure and vice versa. Pressure difference causes horizontal movement of air called wind and vertical movement of air called current, which together cause circulation of air in the atmosphere.

Question 4.
Name the various forms of precipitation.
Answer:
Rain, drizzle, snow, sleet, and hail are all different forms of precipitation.

Question 5.
How is cloud cover shown on a weather map? Give examples.
Answer:
The cloud cover in the sky is expressed in eighths of the total sky or oktas, which are shown in weather maps as discs shaded in different proportions.

D. Answer the following questions in one or two paragraph’s.

Question 1.
How is weather different from climate?
Answer:
Weather and climate are closely related terms but have different
meanings. Weather refers to the atmospheric conditions of a small area for a short period of time, usually 24 hours or one day, while climate is the average of the atmospheric conditions of a larger area, over a long period of time, usually 35 years.

Question 2.
What is condensation? Explain these different forms of condensation: fog, mist, and dew.
Answer:
Condensation is the process by which water vapour in the air gets converted into tiny droplets of water or ice. It is the opposite of evaporation. Evaporation takes place when air is dry, but condensation occurs only after air is saturated.
Fog and mist are formed at night, when air cools below its dew point near the earth’s surface. Fog is denser than mist and often dangerous because it reduces visibility. Dew forms in winter when the temperature is very low, but not below 0°C.

Question 3.
What do you understand by the term ‘4 o’clock showers’?
Answer:
In regions closer to the equator, the rate of evaporation is very high. Air gets heated because of the high temperature and starts rising in the form of convection currents. As it rises, it expands and cools. The cooling causes condensation, which results in heavy downpours. This rain is accompanied by thunder and lightning and since it mostly occurs around 4 p.m., it is often called the 4 o’ clock showers’.

Question 4.
What are planetary winds? Give a brief description of the Westerlies in the northern hemisphere.
Answer:
Planetary winds are also called permanent or prevailing winds as they blow the year round in the same areas. Westerlies blow in the middle latitudes between 30° and 60° latitude, and originate from the high pressure area in the horse latitudes towards the poles. Under the effect of the coriolis force, they become the South Westerlies in the north hemisphere and Northern Westerlies in the southern hemisphere.

Question 5.
What are local winds? Give a few examples.
Answer:
Local Winds blow for a short period of time over a very small area. Some local winds like Loo, Simoom, Chinook, and are warm winds. Others such as the Bora, Mistral, Buran, and Pampero are cold winds.

E. With the help of your atlas,encylopaedias, and the Internet, find out about the climate of these places.

1. Mumbai
2. Delhi
3. Kolkata
4. London
5. New York
6. Sydney

F. In your notebook, draw neat, labelled, coloured sketches of the three different types of rainfall. Alongside each diagram, briefly describe in your own words, how each type of rainfall occurs.
Answer:

(a) Convectional Rainfall : In regions closer to the equator, the rate of evaporation is very high. Air gets heated because of the high temperature and starts rising in the form of convection currents. As it rises, it expands and cools. The cooling causes condensation, which results in heavy downpours. This rain is accompanied by thunder and lightning and since it mostly occurs around 4 p.m., it is often called the 4 o’clock showers’.

(b) Relief or Orographic Rainfall : Sometimes moisture-bearing winds are forced to rise because of the presence of a physical

expands and cools, and the moisture in it condenses to form clouds. These clouds bring rainfall.

G. Picture study

Question 1.
The diagram alongside illustrates one of the factors that affect temperature. What is it ?

Answer:
Aspect refers to the direction of a slope with respect to the sun’s rays. In the northern hemisphere, all the south-facing slope receive the direct rays of the sun and are, therefore, warmer, while the north-facing slopes are cooler. In the southern hemisphere, all the north-facing slopes receive more sunlight than the south-facing slopes.

Question 2.
Which side of the mountain is likely to have houses and be covered with trees ?
Answer:
Side B.

ICSE Solutions for Class 7 Geography Voyage – Africa: Climate, Natural Vegetation, Wildlife; Minerals

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 7 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 7 with Free PDF download option. Geography Voyage for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

ICSE Solutions Class 7 Geography History & CivicsMathsPhysicsChemistryBiology

THINK AND ANSWER

The northern and southern parts of Africa have opposite seasons at any time of the year. Why ?
Answer:
A large part of Africa lies between the tropics, and, therefore, most of the continent has a warm or hot climate. However, the amount of rainfall and humidity varies from area to area.
Anoteworthy feature ofthe climate of Africa is that the northern and southern parts of the continent have opposite climates at any time ofthe year. In other words, when the northern part experiences summer, the southern part experiences winter.

Discuss

Discuss how the location of Africa has affected the climate ofthe country.
Answer:
Since most of Africa lies within the tropics, the temperatures are high throughout the year. The variations between summer and winter temperatures are only slight.

VALUES AND LIFE SKILLS

Africa rainforests are one of the densest forests on earth. A large number of trees grow in a relatively small area because the region receives a lot of rain and sunshine, both importance for the growth of plants. Human being also fourish when they get the right conditions.
Can you enlist a few factors that affect the growth of human beings ?
What factors adversely affect the growth of people in an area ?
Answer:
The factors that affect the growth of human beings are :

1. Proper balanced and nutrionational diet.
2. Proper health and sanitary facilities.
3. Proper temperature.

The factors that adversely affect the growth of people in an area are :

1. Poor or unhealthy diet.
2. Poor sanitation
3. Poor water facilities
4. Lack of awareness.

EXERCISES

A. Write True or False. Correct the false statements.

1. Nights are very hot in the Sahara Desert.
Answer. False.
Nights are very cold in the Sahara Desert.

2. The cold Canaries Current washes the north-west coast of Africa ?
Answer. True.

3. Savannah is another name for the Sudan type of climate.
Answer. True.

4. Temperate grasslands have dry, tall grasses.
Answer. False.
Temperate grasslands have green, short grasses.

5. The Kalahari Desert is located in north Africa.
Answer. False.
The Kalahari Desert is located in south-central Africa.

B. Give geographical reasons.

Question 1.
The equatorial region has dense forests.
Answer:
The equatorial region has dense forests as trees grow in this region to different heights, giving an impression of a three-tier formation. The topmost layer is the emergent layer. The giant trees thrust above the dense layer of trees and have huge mushroom shaped crowns. The trees in this layer receive a lot of sunlight and rain. The second layer is the canopy layer. The broad irregular crown of these trees form a tight, continuous canopy 20-30 m above the ground. The branches are often densely covered with other plants and tied together with vines.
The third layer is the understorey, which receives very little sunlight and is very dark. It has young trees, shrubs, ferns, creepers, and orchids. The forest floor usually has a layer of decomposed leaves, branches, and fruits that have fallen from the trees above. As there is very little sunlight here, the growth of plants is poor. Thus, these forests are very dense and gloomy.

Question 2.
The grasses of the savannah and the veldt are different.
Answer:
Veldts or temperate grasslands are found in South Africa. The vegetation consists of short grasses, less coarse and green than those in the savannahs. On the hill slopes, poplars and willows are common.

Question 3.
Plants in the Sahara are thorny and dry.
Answer:
Plants in the Sahara are thorny and dry as these plants have thorny leaves, thick waxy stems, and long thin roots which penetrate deep for underground water.

Question 4.
Not much wildlife is found in the Mediterranean region ofAfrica.
Answer:
Not much wildlife is found in the Mediterranean as the forests in the Mediterranean region are not extensive and most of the natural vegetation has been cut down, not much wildlife is found in the this region.

C. Answer the following questions in brief.

Question 1.
Most ofAfrica is hot. Why ?
Answer:
A large part of Africa lies between the tropics, and, therefore, most of the continent has a warm or hot climate. However, the amount of rainfall and humidity varies from area to area.

Question 2.
What factors influence the climate of Africa ?
Answer:
The factors that affects the climate of Africa are latitudinal extent, land and sea contrast, ocean currents, and altitude.

Question 3.
Name a cold and a warm current that affect the climate of Africa.
Answer:
The cold Canaries Current washes the north-west coast of Africa, while the cold Benguela Current washes the shores of south-west Africa and has a cooling influence on the adjacent land. Winds blowing over these cold currents become cold and do not pick up moisture.

Question 4.
What are 4 o’clock showers ? In which climatic region of Africa do they occur ?
Answer:
This type of climate is found in the lowlands on either side of the equator in the Congo Basin, the coastal region around the Gulf of Guinea and coastal Kenya. The climate is characterized by a high temperature of 27°C throughout the year and heavy annual rainfall of200-250 cm. Thus, there is high humidity all through the year and there are no clearly marked seasons. There is a daily occurrence of convectional rainfall. This type of rainfall is the result of intense heating of the land surface. During the day, there is a lot of evaporation. By afternoon, when it starts cooling, the water vapour condenses and falls as rain. Since it pours around 4 o’clock every day, it is known as ‘4 o’clock showers’.

Question 5.
Which region is called an open air zoo ? Why ?
Answer:
Savannah or Tropical sub-humid type of region is often referred to as an open air zoo.
The savannah has vast grassy plains with tall, coarse grasses. Many herbivorous animals such as giraffes, elephants, and zebras and carnivorous animals such as lions, cheetahs, and leopards are found here in large numbers and, therefore, this region is referred to as an open air zoo.

D. Answer the following questions in one or two paragraphs.

Question 1.
Describe the three-tier forest of the equatorial region.
Answer:
The equatorial region has dense forests. Trees grow in this region to different heights, giving an impression of a three-tier formation. The topmost layer is the emergent layer. The giant trees thrust above the dense layer of trees and have huge mushroom shaped crowns. The trees in this layer receive a lot of sunlight and rain. The second layer is the canopy layer. The broad irregular crown of these trees form a tight, continuous canppy 20-30 m above the ground. The branches are often densely covered with other plants and tied together with vines.
The third layer is the understorey, which receives very little sunlight and is very dark. It has young trees, shrubs, ferns, creepers, and orchids. The forest floor usually has a layer of decomposed leaves, branches, and fruits that have fallen from the trees above. As there is very little sunlight here, the growth of plants is poor. Thus, these forests are very dense and gloomy. The hardwood trees are valuable for making good quality furniture as the wood is heavy, but the trees are difficult to exploit as they do not grow in pure stand.

Question 2.
Give examples of herbivorous and carnivorous animals found in the savannah grasslands.
Answer:
Herbivorous animals such as the elephant, deer, giraffe, and zebra and carnivorous animals such as the lion, cheetah, and leopard are found in large numbers.

Question 3.
Identify the hot deserts of Africa and briefly describe the climatic conditions in terms of temperature and rainfall.
Answer:
Summers are hot and winters are cool in the hot desert regions. The daily as well as annual range of temperature is large-due
to the absence of cloud cover and the sandy nature of the soil. There is hardly any rainfall. These climatic conditions are found both in the northern and the southern hemispheres. In north Africa it is mainly experienced in the Sahara Desert and in south-central Africa in the Kalahari Desert.

Question 4.
Why is the camel called ‘the ship of the desert’ ?
Answer:
The camel is called ‘the ship of the desert’ for the following reasons:

1. It carries goods and people across the vast sandy deserts.
2. It stores fat in its hump.
3. Its padded feet prevent it from sinking in the sea of sand.
4. It has double eyelids and long eyelashes to protect its eyes from sand during storms.
5. It can close its nostrils during sandstorms.

Question 5.
Describe the Mediterranean climate.
Answer:
The coastal areas of north-west Africa and a small area in the south-west of South Africa experience the Mediterranean climate. Summers are hot with plentiful sunshine but no rainfall. Winters are mild and wet. Shifting Westerlies bring rain to these regions in their respective winter seasons.

E. In the outline map of Africa give here, mark the features and answer the questions.

Question 1.
Colour dark green the area where equatorial forests are found. What difficulties were faced by the explorers because of rivers and natural vegetation of the region ?
Answer:
The equator passes through the middle of the continent and most of Africa lies within the tropics. It is, therefore, the hottest continent.
People faced many difficulties while exploring Africa. In the north, the Sahara, the world’s largest desert, was impenetrable due to severe heat and dry conditions. Most of Africa consists of undulating plateaus, so it was difficult to reach the interior from the coastal areas. The rivers of Africa have many rapids and waterfalls, and are not fit for navigation. The extensive equatorial forests and swampy lands teeming with dangerous tsetse flies and poisonous insects discouraged explorers from entering the heart of the continent.

Question 2.
Mark the area that is called an ‘open air zoo’. Name thevegetation of this region.
Answer:
These vast grassy plains with tall, coarse grasses are called the savannahs or tropical grasslands. Several varieties of grass, including elephant grass, grow here. Some acacia and baobab trees are found interspersed between the grasses. Please check Map given on Textbook page 126 (Africa : Climatic and vegetation regions)

Question 3.
Mark the Sahara Desert. Name a plant that best survives in the climate of this region. What are the characteristic features of this plant that help it survive ?
Answer:
The trees have long roots, small waxy leaves, and thick spongy bark, which help them survive in the dry summers. Examples include cork, oak, laurel, olive, and fig. Forests are not extensive as most of them have been cut down and replaced by orchards of citrus fruit trees such as oranges, lemons, and grapes.

Question 4.
Mark the area north of the Atlas Mountains where the Mediterranean climate is found. Which crops does this climate support ?
Answer:
The trees have long roots, small waxy leaves, and thick spongy bark, which help them survive in the dry summers. Examples include cork, oak, laurel, olive, and fig. Forests are not extensive as most of them have been cut down and replaced by orchards of citrus fruit trees such as oranges, lemons, and grapes.

F. Picture study

Question 1.
What kind of climate is experienced in the region shown in the picture ?
Answer:
Summers are hot and winters are cool in the hot desert regions. The daily as well as annual range of temperature is large due to the absence of cloud cover and the sandy nature of the soil. There is hardly any rainfall. These climatic conditions are found both in the northern and the southern hemispheres. In north Africa it is mainly experienced in the Sahara Desert and in south-central Africa in the Kalahari Desert.

Question 2.
What kind of vegetation grows in such a climate ?
Answer:
The trees have long roots, small waxy leaves, and thick spongy bark, which help them survive in the dry summers. Examples include cork, oak, laurel, olive, and fig. Forests are not extensive as most of them have been cut down and replaced by orchards of citrus fruit trees such as oranges, lemons, and grapes.

Question 3.
Fill in the blanks : The animal seen in the picture is often referred to as the _____ of the _____
Answer:
Fill in the blanks: The animal seen in the picture is often referred to as the ship of the desert.

ICSE Solutions for Class 7 Geography Voyage – Recording of Weather

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 7 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 7 with Free PDF download option. Geography Voyage for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

ICSE Solutions Class 7 Geography History & CivicsMathsPhysicsChemistryBiology

Discuss

How are dew drops beneficial for plants ?
Answer:
In the early morning dew surrounds the leaves of plant with moisture and plant does not close its stomata.

EXERCISES

A. Answer the following questions in brief

Question 1.
What is relative humidity? How does it differ from absolute humidity ?
Answer:
Relative humidity is the ratio of the actual amount of water vapour present in the air and the total amount the air can hold at a given temperature. It is expressed in percentage.
While absolute humidity is measured in grams per cubic metre.

Question 2.
What does a large difference between the temperatures of a dry bulb thermometer and a wet bulb thermometer of a hygrometer indicate?
Answer:
A large difference between the readings of the two thermometers means low relative humidity and a small difference between them means high relative humidity.

Question 3.
Differentiate between precipitation and condensation. Give one example of each.
Answer:
Condensation – Dew is a form of condensation. Condensation is the process by which water vapour in the air gets converted into tiny droplets of water or ice. Dew formsin winters when the temperature is very low but not below 0°C. Moist air comes in contact with the cold surfaces near the ground. The water vapour in the air changes to water and we see it as dew drops on grass or on plants. Dew drops are beneficial for plants. Precipitation – Precipitation is the falling of atmospheric moisture as a result of condensation. It has many forms such as rainfall, snowfall, and hail.

Question 4.
What are nimbus clouds?
Answer:
Nimbus are real rain clouds-thick, dark and black and spread out in layers. They cause continuous rain or snow.

Question 5.
What is the Beaufort scale?
Answer:
Beaufort scale is the scale that is used to estimate wind speed. The scale is based on the effect of the wind at different speeds.

B. Answer the following questions in one or two paragraphs

Question 1.
What is a hygrometer ?
Answer:
The instrument used for measuring relative humidity is called hygrometer. The hygrometer consists of wet and dry bulb thermometer. The dry bulb thermometer is an ordinary thermometer while the wet bulb thermometer is kept wet by a wick that dips into a container of distilled water. The wet bulb thermometer shows the lower temperature than the actual temperature as evaporation from the moist wick has a cooling effect. A larger difference between readings of two thermometers means low relative humidity and small difference means high relative humidity.

Question 2.
Describe the various types of clouds.
Answer:
The four types of clouds are :

(a) Cirrus clouds — These are feathery, fibrous clouds which form at very high levels of 5 to 10 km. They consist of tiny crystals of ice and look like wisps of cotton floating in the sky.
(b) Cumulus clouds — These are cauliflower-shaped clouds that have great vertical height and a flat base; they cause rainfall with lightning and thunder, and are usually white or grey in colour.
(c) Stratus clouds — These are sheet-like clouds that spread out 42 Arundeep’s Self-Help to Voyage-7 over the whole sky. They usually form at low levels, less than 2 km. They are uniformly grey and dull.
(d) Nimbus clouds — These are the real rain clouds – thick, dark and black, and spread out in layers. They cause continuous rain or snow.

Question 3.
What is wind? What precautions must be taken while placing a wind vane?
Answer:
Wind is air in motion. A wind vane indicates the direction of the wind and consists of a rotating arm pivoted on a vertical rod. The arrow of the wind vane always points in the direction from which the wind blows and the wind is named accordingly. For example, if the pointer is pointing to the East, the wind is blowing from East to West and, therefore, this wind is called an easterly wind. Wind vanes are usually placed away from obstacles such as high buildings, trees, etc.

Question 4.
What are isohyets and isotherms ?
Answer:
Isohytes : A weather map, which shows, by the help of lines, the amount of rainfall a place receives. Each of these lines is made by joining points that show the same amount of rainfall received in a given period. These lines are known as isohyets.
Isotherm : On the map, places experiencing the same temperature at a given time are connected with a line. This line is known as an isotherm. Each of these points on the line reflects one temperature reading, or an average of several readings, over a period of time.

Question 5.
What is a weather report ? How is weather forecast made? Why is weather forecast necessary ?
Answer:
When the weather conditions of the previous day are published, it is called a weather report. Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Nowadays it is made with the help of data gathered from weather satellites and radar systems. Forecasts help to plan what to wear, when to travel or which products to stock in super markets. It’s specially important for farmers, builders, sailors or anyone else who works out doors.

C. For a week, gather information on the weather conditions of your city using simple instruments or from weather reports published in newspapers. Present this information in a table. One has been done for you here. My observation of the weather at for a week.

D. This could be a classroom activity. If your school laboratory has an anemometer, use it to record your city’s wind speed for a week. Use the Beaufort Scale to find out the character of wind during these days. Record your observations carefully in your notebook. You could even draw small neat sketches to show the effect of the wind.
Answer:
Do it Yourself

E. From the weather report published in your local newspaper, record the time of sunrise and sunset for a month in your notebook, as shown on the next page : My observation of the time of sunrise and sunset for the month of ______ 20, ______

F. Picture Study

1. Identify the four types of clouds shown in the photographs.
2. Which of these causes heavy rainfall?

Answer:

1.(a) Cirrus clouds
(b) Cumulus clouds
(c) Stratus clouds
(d) Nimbus clouds

2. Nimbus clouds causes heavy rainfalls.

ICSE Solutions for Class 7 Geography Voyage – Types of Rocks

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APlusTopper.com provides step by step solutions for ICSE Solutions for Class 7 Geography Voyage. You can download the Voyage Geography ICSE Solutions for Class 7 with Free PDF download option. Geography Voyage for Class 7 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines.

ICSE Solutions Class 7 Geography History & CivicsMathsPhysicsChemistryBiology

THINK AND ANSWER

Why is diamond clear and hard while graphite is soft ? Why is coal hard and chunky ?
Answer:
Carbon atoms in diamond are bonded in a strong tetrahedron pattern making it hard and clear whereas carbon atoms in graphite are bonded in weak covalent bonds making it soft and black. Coal is a combustible sedimentary rock occurring in rock strata in layers or veins called coal beds. Because of pressure and elevated temperature the carbon becomes hard and chunky.

Discuss

Discuss the importance of rocks for the contruction business.
Answer:
Rocks such as marble and granite are used in construction industries. They are cut into stones and are used for building houses, dams, roads, etc. Rocks also provide raw materials such as limestone and gypsum used in the manufacturing of cement.

VALUES & LIFE SKILLS

Rocks and minerals play a very important role in our lives.
Can you imagine modern life without minerals ?
What problems would you face in their absence ?
Answer:
Life without rocks and minerals would be disastrous –
Rocks are of great value to us. Some of the main benefits of- rocks are listed below :

• Soil is formed when rocks gradually break up and disintegrated by mechanical and chemical processes.
• Rocks contain a great variety of minerals that yield metals such as iron, manganese, and copper, which are important raw materials for
  mineral-based manufacturing industries.
  We shall face many problems if rocks and minerals get diminished.

The following problems may exist:

1. Human life will come to an end, as soil is essential for food production and if rocks diminished, it would lead to non¬availability of soil.
2. Mineral-based manufacturing industries will also come to an end.

EXERCISES

1. Granite is an example of intrusive igneous rocks.
2. A category of rock which is formed by the alteration of the parent rock due to heat and pressure is called: metamorphic rocks.
3. Conglomerate is an example of sedimentary rocks. .
4. Sedimentary rocks are formed from sediments accumulated over long periods.
5. Sedimentary rock such as limestone change into marble.

B. Write True or False. Rewrite the false statements correctly :

1. Minerals are organic substances.
Answer. False.
Correct : Minerals are inorganic substances.

2. Basalt is an example of an intrusive igneous rock.
Answer. False.
Correct : Basalt is an example of an extrusive igneous rock.

3. Sedimentary rocks are formed by the cooling and solidification of molten rock called magma.
Answer. False.
Correct : Igneous rocks are formed by the cooling and solidification of molten rock called magma.

4. Igneous and sedimentary rocks can change into metamorphic rocks.
Answer. True.

5. Rocks are used in construction industries.
Answer. True.

C. Answer the following questions in brief:

Question 1.
What is crust ?
Answer:
The outermost layer of the Earth is the crust. Crust is the thinnest layer of the earth.

Question 2.
Differentiate between SIAL and SIMA.
Answer:
SIAL

1. It is the upper layer of the earth.
2. it is made up of silica and aluminium.

SIMA

1. It is the lower layer of the earth.
2. It is made up of magnesium and silica.

Question 3.
State two characteristics of the mantle.
Answer:

1. The mantle is semi-solid.
2. It is rich in iron and magnesium.
3. This layer is about 2,850 km wide. Its average density is between 3.5 and 5.5.

Question 4.
What is the difference between the inner and the outer core ?
Answer:
Inner core

1. Inner most layer of the Earth.
2. Solid ball of iron and nickel.
3. Has a radius of 1220 km.

Outer core

1. Surrounds the inner core.
2. Made of liquid iron and nickel.
3. Has a radius of Approx. 2300 km.

Question 5.
What are minerals?
Answer:
Minerals are natural inorganic substances having a crystalline form with definite physical and chemical properties. The most common minerals in the earth’s crust are silica, quartz, feldspar, mica, calcite, dolomite, gypsum, etc. There are about 2,000 minerals in the earth’s crust and these combine differently to form various kinds of rocks.

Question 6.
Give an example of an intrusive igneous rock.
Answer:
Instrusive rocks, which form large crystals at some depth in the earth’s crust example : granite, basalt.

Question 7.
Classify the following rocks as igneous, sedimentary, and metamorphic: gneiss, coal, shale, granite, gypsum, marble, sandstone, basalt, limestone, schist
Answer:
Minerals — Rocks
Gneiss — Metamorphic
Coal — Sedimentary
Shale — Sedimentary
Granite — Igneous
Gypsum — Sedimentary
Marble — Metamorphic
Sandstone — Sedimentary
Basalt — Igneous
Limestone — Sedimentary
Schist — Metamorphic

D. Answer the following questions in one or two paragraphs :

Question 1.
Explain the structure of the earth’s interior ?
Answer:
The earth’s interior is divided into three main layers — the crust is the outermost layer, the mantle is the intermediate layer, and the core is the innermost layer of the earth.

Question 2.
How are rocks different from minerals?
Answer:
Minerals are natural inorganic substances having a crystalline form with definite physical and chemical properties whereas rocks are made up of a combination of different minerals compacted together. There are about 2,000 minerals in the earth’s crust and these combine differently to form various kinds of rocks.

Question 3.
How are igneous rocks formed?
Answer:
Igneous rocks are formed by the cooling and solidification of molten rock called magma, which lies beneath the earth’s crust. These rocks are crystalline and compact. They do not occur in layers or strata nor do they contain fossils.
The cooling and solidification may take place at some depth within the earth or at the surface. The molten magma that reaches the surface of the earth is called lava. Thus, there are two types of igneous rocks classified on the basis of their place of origin – intrusive rocks, which form at some depth in the earth’s crust and extrusive rocks which form at or near the surface of the earth.

Question 4.
How do acidic igneous rocks differ from basic igneous rocks ?
Answer:
Igneous rocks may also be classified as acidic or basic depending on their composition. The acidic rocks contain more than 65% silica and very low percentage of oxides. These are Arundeep’s Self-Help to Voyage-7 less dense and light coloured. For example, granite. The basic rocks contain low percentage of silica and high percentage of oxides. These are dense and dark coloured. For example, basalt.

Question 5.
How are sedimentary rocks formed ?
Answer:
Sedimentary rocks are formed from sediments accumulated over long periods, usually under water on the floors of shallow seas, rivers and lakes. These rocks are non-crystalline and are found in layers or strata and contain fossils. Conglomerate, sandstone, limestone, chalk, calcite, and dolomite are example of sedimentary rocks. Sedimentary rocks are divided into various types depending on how they are formed.

1. Mechanically formed sedimentary rocks :
   These rocks have been formed by the accumulation of materials derived from other rocks which have been cemented together.
   Examples – conglomerate (rounded fragments), breccia (angular fragments).
2. Organically formed sedimentary rocks :
   These rocks have been formed by the accumulation of the remains of living organisms.
   Examples – calcareous rocks such as limestone and chalk.
3. Chemically formed sedimentary rocks:
   These rocks have been commonly formed by the process of evaporation of water containing salts in solution.
   Examples – rock salt, gypsum, potash, nitrates, calcite, and dolomite.

Question 6.
What are metamorphic rocks ?
Answer:
Metamorphic rocks are those rocks which are formed by the metamorphism of pre-existing rocks due to high temperature or pressure or both. Igneous and sedimentary rocks completely changes over long periods of time because of movements in the earth’s crust and volcanic or mountain building activity.
Transformation of rocks due to high temperature is called thermal metamorphism. Alteration of parent rock due to pressure exerted on rocks from the earth’s movements is called dynamic metamorphism.

E. Picture study

The photograph shows you a type of rock that is widely used in the construction industry.

Question 1.
Name the type of rock.
Answer:
The type of rock is chemically formed sedimentary rock as limestone becomes marble. It is marble.

Question 2.
How is it formed ?
Answer:
Sedimentary rocks are formed from sediment accumulated over long periods, usually under water on the floors of shallow seas, rivers, and lakes. These rocks are fromed by the process of evaporation of water containing in limestone which becomes marble.

LET’S DO SOMETHING

With the help of your teacher, collect different types of rocks such as granite, sandstone, limestone, marble, slate, graphite, etc. and prepare a chart containing information about their colour, hardness, texture, and permeability.
Answer:
Do it Yourself.

ICSE Solutions for Class 7 Geography Voyage – Australia:Location,Area, Political & Physical Features

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DISCUSS

Why are the Eastern Highlands called the Great Dividing Range ?
Answer:
The Eastern Highlands are also called the Great Dividing Range because the mountains form the main watershed of Australia. A number of Australia’s principal rivers originate here. The Snowy River flows down the steep eastern slope while the Darling, Lachlan, and Murrumbidgee Rivers flow down the western slope and join the Murray River.

THINK AND ANSWER

Why can’t Australia’s exotic flora and fauna be found anyw here else in the world ?
Answer:
Australia is a natural wonderland of beautiful beaches, crystal blue waters, amazing ancient rock formations and pristine rain forests. Australia is the sixth largest country in the world and has the lowest population density per square kilometer. Australia has 16 world heritage listed properties with its historic townships, bustling cities, vivid landscapes and exotic flora and fauna all adding to its unique appeal. Most of Australia’s exotic flora and fauna cannot be found anywhere else in the world and the lifestyle is one second to none.

EXERCISES

A. Fill in the blanks

Australia is located between latitudes 10°S and 40°S and , between longitudes 114°E and 154°E. So, this Island continent lies wholly in the Southern hemisphere. Australia is the sixth largest country in the world but is the smallest continent. The name Australia comes from the Latin word ‘Australis’ meaning Southern. The official name is the Commonwealth of Australia. Some other popular names are the ‘Land of Migrants’ and the ‘Island Continent’.

B. Choose the correct answer

1. The Great Dividing Range is so called because:

1. it divides Australia into two halves
2. it is very high
3. it acts as a watershed between the rivers flowing to the east and those flowing westwards

2. The Lake Eyre Basin is called an area of inland drainage because :

1. the area keeps changing
2. the rivers flowing in this area have no outlet to the sea
3. it is a low-lying lake

C. Answer the following questions in brief

Question 1.
Name the water bodies that surround Australia.
Answer:
Australia lies between the Indian Ocean in the west and the_ South Pacific Ocean in the east.

Question 2.
Identify and name the important line of latitude that passes through the middle of Australia.
Answer:
The tropic ofCapricom or 231/2 °S latitude passes through the middle of Australia.

Question 3.
Why are the Eastern Highlands also called the Great Dividing Range?
Answer:
The Eastern Highlands are called the Great dividing range because the mountains here form the main watershed of Australia. A number of Australia’s principal rivers originate here.

Question 4.
What is an ‘aquifer’?
Answer:
A porous layer of rock capable of storing water and allowing its passage is called aquifer.

Question 5.
What is meant by ‘inland drainage’? Give an example.
Answer:
Inland drainage is that drainage in which the rivers do not reach an ocean or sea and drain in a lake or an ‘inland’ sea, e.g. Lake Eyre.

Question 6.
Which breed of sheep is mainly reared in Australia ?
Answer:
The merino breed of sheep, which produces the best fleece for wool, is mainly reared in Australia.

Question 7.
Identify the four main sheep-rearing states of Australia.
Answer:
The main sheep-rearing states are New South Wales, Victoria, Western Australia, and South Australia.

D. Answer the following questions in one or two paragraphs

Question 1.
Mention two differences between the rivers that flow down the western and eastern slopes of the Great Dividing Range.
Answer:
The Great Dividing range in the east divides the flow of rivers in the region. The rivers that flow down the eastern slopes’ are short and perennial and drain into Pacific Ocean. The rivers that flow down the western slopes are longer and flow to central lowlands and have inland drainage.

Question 2.
Explain an artesian basin and an artesian well.
Answer:
Artersian basin is a layer of porous or pervious rock lies between two layers of impervious rocks and acts as a reservoir. The rain water seeps underground and the rock becomes capable of holding water and allowing it to pass through it called aquifer. A well is bored into the aquifer through which water rises to the surface by natural pressure is called artesian well.

Question 3.
Why is most of the underground water not suitable for human consumption agriculture?
Answer:
Most of the underground water is not suitable for irrigation and human consumption as the water is salty and is present in the artesian basin of Australia.

Question 4.
How are corals formed?
Answer:
Corals are a hard substance composed of skeleton of tiny marine creatures called coral polyps. When corals die their hard skeletons remain fixed in place. Since these polyps live in colonies, when they die their large accumulation of skeletons form coral reefs which are circular or ridge-like.

Question 5.
Write three interesting points about the Great Barrier Reef.
Answer:
Some Important points about the Great Barrier Reef are:

1. The Great Barrier Reef is a 2,300 km long underwater ridge-like feature off the north-east coast of Australia at distance varying from 16 to 240 km from the coastline.
2. It is composed of millions and millions of shells of tiny marine creatures called coral polyps.
3. The Great Barrier Reef is Australia’s biggest tourist attraction. The warm, shallow, salty sea between the reef and the shore is the home of tropical fish of bright colours, and crustaceans that abound in this underwater paradise.

E. Map work
On the outline map of Australia given here, neatly mark and label the following :

1. the capital cities of the states
2. The narrow stretch of water that separates Tasmania from Australia
3. The longest perennial river of Australia
4. The ocean that lies west of Australia
5. A ridge-like feature made up of coral
6. write SHEEP FARMING in an appropriate place on the map where it is practised.

Answer:

F. Picture Study

This is a photograph of Australia’s Great Barrier Reef. Why do you think this reef is Australia’s biggest tourist attraction.

Answer:
because its home for bright coloured tropical fishes and crustaceans that abound in this underwater paradise.

LET’S DO SOMETHING

Question 1.
On an outline map of Australia, mark the boundaries of South Wales-Victoria border different from the other borders ? Find out why.
Answer:
The boundaries of all the states except South-wales and Victoria border are same divided with a straight line.
The reason behind the border not being straight is that the majority of the border between Victoria and New South Wales is formed by the River Murray (Interestingly the river is actually in New South Wales entirely, instead of the border being right through the centre of the river). It doesn’t form the border between South Australia and Vic/NSW or any of the other states as it either doesn’t run through the states or, like in South Australia, cuts right through the initial territory designated for the free colony. As they didn’t want to form another state they just kept SA as it was and had the river running through it.
But essentially, the border is formed by the Murray, which, as a river, naturally isn’t a straight line.

Question 2.
Collect information about the Great Barrier Reef from encyclopaedias or the Internet and write a diary describing all you have learnt about it in your scrapbook.
Answer:
The Great Barrier Reef is one of the seven wonders of the natural world, and pulling away from it, and viewing it from a greater distance, you can understand why. It is larger than the Great Wall of China and the only living thing on earth visible from space.
Where Is The Great Barrier Reef ?
The marine park stretches over 3000km (1800 miles) almost parallel to the Queensland coast, from near the southern coastal town of Bundaberg, up past the northern tip of Cape York.
The reef, between 15 kilometres and 150 kilometres off shore and around 65 Km wide in some parts, is a gathering of brilliant, vivid coral providing divers with the most spectacular underwater experience imaginable.
A closer encounter with the Great Barrier Reefs impressive coral gardens reveals many astounding underwater attractions including the world’s largest collection of corals (in fact, more than 400 different kinds of coral), coral sponges, molluscs, rays, dolphins, over 1500 species of tropical fish, more than 200 types of birds, around 20 types of reptiles including sea turtles and giant clams over 120 years old.

What Is The Great Barrier Reef ?
The reef is a breeding area for humpback whales, migrating from the Antarctic and is also the habitat of a few endangered species including the Dugong (Sea Cow) and large Green Sea Turtle. In recognition of its significance, UNESCO listed the Great Barrier Reef as a World Heritage Site in 1981.
Because of its natural beauty, both below and above the water’s surface, the reef has become one of the worlds most sought after tourist destinations.
In 2006 there were approximately 820 operators and 1500 vessels and aircraft permitted to operate in the Great Barrier Reef Marine Park providing ease of access for all to experience the Great Barrier Reef and learn first hand about its natural delights and World Heritage values.
One of Australia’s most remarkable natural gifts, the Great Barrier Reef is blessed with the breathtaking beauty of the world’s largest coral reef. The reef contains an abundance of marine life and comprises of over 3000 individual reef systems and coral cays and literally hundreds of picturesque tropical islands with some of the worlds most beautiful sun-soaked, golden beaches.Because of its natural beauty, the Great Barrier Reef has become one of the worlds most sought after tourist destinations. A visitor to the Great Barrier Reef can enj oy many experiences including snorkelling, scuba diving, aircraft or helicopter tours, bare boats (self-sail), glass-bottomed boat viewing, semi-submersibles and educational trips, cruise ship tours, whale watching and swimming with dolphins.
A Natural Wonder :
The Great Barrier Reef is one of the seven wonders of the natural world, and pulling away from it, and viewing it from a greater distance, you can understand why. It is larger than the Great Wall of China and the only living thing on earth visible from space.