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In This Post we are  providing  CHAPTER 10 ATMOSPHERIC CIRCULATIONS AND WEATHER SYSTEMS NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON ATMOSPHERIC CIRCULATIONS AND WEATHER SYSTEMS

Question 1.
What is a jet stream? Explain.
Answer:
The winds with a high velocity which blow at high altitude are called the jet stream. This strong current of air is located near 90° north latitude. It affects the weather patterns of the world. High flying planes use these as super tailwinds to save time and fuel.

Question 2.
Describe the local winds in brief.
Answer:
Winds having special characteristics under local conditions are known as local winds.

1. Hot winds: Chinook in Canada and USA, foehn in Switzerland.
2. Dry winds: Sirocco in south Europe, Khanzim in Egypt, Hermatton in West Africa, Simoon of Arabia, Santa Anna of California, Zenda of Argentina.
3. Cold winds: Boro and Mistral in Southern Europe, Pampero in Argentina, Buran in Siberia.

Question 3.
Write a short note on ‘doldrums’.
Answer:
The doldrum is an equatorial low-pressure belt between 5°N to 5°S latitudes. It is known as the-belt of calm. The air is constantly heated due to the high temperature. The air expands and rises as convection currents. There are no surface winds. Sailing ships often found them becalmed in this belt due to the absence of backing winds.

Question 4.
What is the importance of air mass?
Answer:
Air mass is important for climatological study. Air masses are related to atmospheric disturbances, cyclones, storms, and fronts.

• The distribution and location of air provide an essential understanding of regional climate.
• Air masses transfer heat from lower latitude to higher latitudes.
• Atmosphericdisturbancesdevelopalongfrontsofdifferentairmasses.
• Air masses are associated with particular types of wind belts and determine the weather characteristics.

Question 5.
What do you understand by valley breeze?
Answer:
The valley breeze occurs during day time. Due to insolation, the valley bottom gets heated. The hot air becomes light and ascends towards the upper slopes. It is known as the valley breeze.

Fig. 10.3: Slopes heated by insolation

Question 6.
Distinguish between:
1. planetary and periodic winds,
2. the sea breeze and land breeze.
Answer:
1. Planetary and periodic winds:
Planetary winds are related to the general circulatory pattern of winds on the rotating earth’s surface. These winds constitute the large-scale motion of the atmosphere under the influence of pressure gradients. They ignore seasonal heating and land-water contrast on the earth’s surface. They are also called permanent or primary wind system of the earth’s surface and comprise trade winds, westerlies, and polar easterlies. These winds blow constantly in a particular direction throughout the year.

Fig. 10.4: Planetary winds

The winds that change their direction periodically with the change in season are called periodic or secondary winds. Monsoon, air masses and fronts, cyclones and anticyclones, land and sea breezes, and mountain and valley breezes are the wind systems that periodically change their courses diurnally or seasonally.

2. Land and sea breezes:
Daily temperature contacts between land and water produce a small diurnal reversal of winds called land and sea breezes. Both are basically caused by differential heating of land and sea.

During the day, the land gets heated up much faster than the sea. The sea remains comparatively cool with higher pressure, so the sea breeze blows in from the sea to land during the day. Its speed is between 5-20 miles/hour and it is generally stronger in tropical than temperate regions.

Its influence does not normally exceed 15 miles from the coast. It is most deeply felt when one stands facing the sea in a coastal area.

At night, the reverse takes place. As the land cools down much faster than the sea, the cold and heavy air produces a region of local high pressure. The sea conserves its heat and remains quite warm. Its pressure is comparatively low. A land breeze thus blows out from land to sea.

Fishermen in the tropics often take advantage of the outgoing land breeze and sail out with it.

Question 7.
Describe the global pattern of the distribution of pressure.
Answer:
The horizontal distribution of pressure, or its global pattern in general, presents an alternate belt of low and high-pressure areas.

There is an inverse relationship between pressure and temperature. The equatorial region having high temperature has low pressure, while the polar regions with low temperature have high pressure. These pressure belts are thermally induced. Logically, there should have been a gradual increase in pressure from the equator towards the poles.

Fig. Pressure belts of the world (See fig.9.1)

There are two intermediate zones of subtropical highs in the vicinity of 30°N and S and two sub-polar lows in the vicinity of 60°N and S. The dynamic control, viz., pressure gradient force, rotation of the earth, are responsible for the formation of these pressure belts.

Thus there are seven pressure belts:

1. An equatorial trough of low pressure.
2. Sub-tropical high-pressure belt (Northern hemisphere)
3. Sub-polar low-pressure belt (Northern hemisphere)
4. Sub-polar low-pressure belt (Southern hemisphere)
5. Sub-tropical high-pressure belt (Southern hemisphere)
6. Polar high (Northern hemisphere)
7. Polar high (Southern hemisphere)

Question 8.
Discuss the seasonal variations in the pressure distribution over the earth’s surface.
Answer:
Despite a broad generalized pattern of pressure distribution on the earth, pressure conditions vary considerably on the basis of prevailing weather conditions in different parts of the world. The horizontal distribution of pressure on the earth’s surface is shown by isobar. Just as there is a daily range of temperature on the surface of tire earth, so there is the diurnal rhythm of pressure.

The direction and rate of change in pressure are called pressure gradient. It is at right angles to isobars, just as the slope of the land surface is at right angles to contour, lines. The rate of change or steepness of the gradient is shown by the spacing of isobars. Closely spacing isobars show’ steep pressure gradient, and widely spaced isobars show’ gentle gradient.

The zonal distribution of pressure is modified by continents and oceans, in summer, the relatively hot continents intensify the low-pressure cells and weaken or destroy high-pressure cells. In a similar manner, the corresponding cooler oceans weaken the low-pressure cells and the high-pressure cells. In winter the situation is reversed. ,

Fig. 10.6: Horizontal distribution of pressure and winds

Question 9.
What are cyclones? Describe the various types of cyclones.
Answer:
Cyclones constitute the most fundamental and climatically the most significant atmospheric disturbances affecting the weather. On the basis of the areas of their origin, they are classified into two types: temperate and tropical.

Temperate cyclones: Temperate1 cyclones are concentrated in the middle latitudes between 35° and 65° in both hemispheres. They are generally extensive having a vertical thickness ranging from 9 to 11 km. and a diameter of about 1,000 km. It is just like a spearhead, having the shape of an upturned ‘V’. The approaching temperate cyclones are noticed by the appearance of dark clouds in the background of white clouds.

According to polar front theory, the highs and lows of westerly wind belts result from the interactions and alteration of two contrasting types of air masses, one in the polar region and the other in the subtropics. Cold air from highs moves toward the equator and is deflected westward, forming the northeast and southeast polar winds. Warmer air from the subtropical highs moves toward the poles and by an eastward deflection from the westerly winds.

Fig. 10.7: Temperate cyclones

As soon as the cyclone approaches, there is drizzle followed by heavy rainfall. The velocity of the wind increases. On the approach of the warm front, the fall in the pressure stops, and the sky becomes clear. This gives the clue that the center of the cyclones has reached. Immediately after this, the temperature begins to fall and the sky becomes cloudy and raining again. This indicates the approach of a cold front.

Tropical cyclones: These are violent storms that originate over tropical seas and move over the coastal areas bringing about large-scale destruction caused by violent winds, very heavy rainfall, and storm surges. They are known as cyclones in the Indian ocean, hurricanes in the Atlantic, typhoons in the western Pacific and South China sea, and willy-willies in west Australia. The conditions favorable for the formation and intensification of tropical storms are:

• Large sea surface with a temperature higher than 27°C.
• Presence of the Coriolis force.
• Small variations in the vertical wind speed.
• A pre-existing weak low-pressure area or low level cyclonic
  circulation.
• Upper divergence above the sea level system.

The cyclone creates stone surges and they inundate the coastland. Over the Indian sea, the cyclonic storms occur in the pre-monsoon

Question 10.
Define and describe the fronts.
Answer:
The contact line between air masses of different properties is called a front. A cold front develops where the cold air mass moves under warm air mass and lifts it up. On the other hand, the trailing edge of a cold air mass that is followed by warm air is called a warm front. In each case, precipitation is likely to occur because warm air is rising over the cold air. Thus duration and intensity of precipitation along the few from.s are quite different. The cold front is steep and produces showery and sometimes violet precipitation for a longer period of time. If the cold front moves faster than the warm front in such a trap, part or all the pocket of warm air may be lifted from the surface, thus producing air occluded front. Often exculpation of the air masses lose earlier characters and form new fronts.

In This Post we are  providing  CHAPTER 11 WATER IN ATMOSPHERE NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON WATER IN ATMOSPHERE

Question 1.
What is convectional rain?
Answer:
Convectional Rain: The air on being heated, becomes light and rises up in convection currents. As it rises, it expands and loses heat and consequently, condensation takes place and cumulous clouds are formed. With thunder and lightening, heavy rainfall takes place but this does not last for long.

Question 2.
What factors influence the process of condensation?
Answer:
Condensation is influenced by the volume of air, temperature, pressure and humidity. Condensation takes place:

• when the temperature of the air is reduced to dew point with its volume remaining constant;
• when both the volume and the temperature are reduced;
• when moisture is added to the air through evaporation.

Question 3 .
Name and define three important types of rainfall.
Answer:
On the basis of origin, rainfall may be classified into three main types:

1. The convectional rain
2. Orographic or relief rain and
3. Cyclonic or frontal rainfall

1. Convectional rain: The air on being heated, becomes light and rises up in convection currents. As it rises, it expands and loses heat and consequently, condensation takes place and cumulous clouds are formed. With thunder and lightening, heavy rainfall takes place but this does not last for long.
Such rain is common in the summer or in the hotter part of the day. It is very common in the equatorial regions and interior parts of the continents, particularly in the northern hemisphere.

2. Orographic rain: When the saturated air mass comes across a mountain, it is forced to ascend and as it rises, it expands; the temperature falls, and the moisture is condensed. In this sort of rain the windward slopes receive greater rainfall. After giving rain on the windward side, when these winds reach the other slope, they descend, and their temperature rises. Then their capacity to take in moisture increases and hence, these leeward slopes remain rainless and dry. The area situated on the leeward side, which gets less rainfall is known as the rain-shadow area. It is also known as the relief rain.

3. Cyclonic rainfall: These rains take place in low pressure areas where air moves from low pressure area to high pressure are a and this movement brings rainfall.

Question 4.
Explain the process of evaporation.
Answer:
Evaporation is a process by which water is transformed from liquid to gaseous state. Heat is the main cause for evaporation. The temperature at which the water starts evaporating is referred to as the latent heat of vapourisation. Increase in temperature increases water absorption and retention capacity of the given parcel of air. Similarly, if the moisture content is low, air has a potentiality of absorbing and retaining moisture. Movement of air replaces the saturated layer with the unsaturated layer. Hence, the greater the movement of air, the greater is the evaporation.

Question 5.
Explain cyclonic rain.
Answer:
Air expands when heated and gets compressed when cooled. This results in variations in the atmospheric pressure. The result is that it causes the movement of air from high pressure to low pressure, setting the air in motion. Air in horizontal motion is wind. Atmospheric pressure also determines when the air will rise or sink. The wind redistributes the heat and moisture across the planet, thereby, maintaining a constant temperature for the planet as a whole. The vertical rising of moist air cools it down to form the clouds and bring precipitation. It is called cyclonic rain.

Question 6.
Differentiate between
Answer:
(i) Precipitation and Condensation.

Basis	Precipitation	Condensation
Meaning	After the condensation of water vapour, the release of moisture is known as precipitation. This may take place in liquid or solid form.	The transformation of water vapour into water is called condensation. Condensation is caused by the loss of heat.
Sequence	Precipitation takes place after condensation.	Condensation takes place before precipitation.
Forms	It may take form of rainfall, snowfall, hailstorms, sleet etc.	It may take form of dew, smog, clouds, fog and mist etc.

(ii) Absolute humidity and Relative humidity.

Basis	Absolute Humidity	Relative Humidity
Meaning	The actual amount of the water vapour present in the atmosphere is known as the absolute humidity.	The percentage of moisture present in the atmosphere as compared to its full capacity at a given temperature is known as the relative humidity.
Unit	It is the weight of water vapour per unit volume of air and is expressed in terms of grams per cubic metre.	It is measured in percentage and hence is unit free.

(iii) Convection rain and Relief rain.

Basis	Convection Rain	Relief Rain
Meaning	The, air on being heated, becomes light and rises up in convection currents. As it rises, it expands and loses heat and consequently, condensation takes place and cumulous clouds are formed. With thunder and lightening, heavy rainfall takes place but this does not last for long.	When the saturated air mass comes across a mountain, it is forced to ascend and as it rises, it expands; the temperature falls, and the moisture is condensed. In this sort of rain is that the windward slopes receive greater rainfall. After giving rain on the windward side, when these winds reach the other slope, they descend, and their temperature rises. Then their capacity to take in moisture increases and hence, these leeward slopes remain rainless and dry.
Timing	Such rain is common in the summer or in the hotter part of the day.	Such rain is common in winters.
Prevalent	It is very common in the equatorial regions and interior parts of the continents, particularly in the northern hemisphere.	It is very common in terrestrial regions.

(iv) Fog and Mist.

Basis	Fog	Mist
Meaning	Fogs are drier than mist.	The mist contains more moisture than the fog.
Prevalent	They are prevalent where warm currents of air come in contact with cold currents.	Mists are frequent over mountains as the warm air rising up the slopes meets a cold surface.
Structure	In mist each nuclei contains a thicker layer of moisture.	Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke, and the salt particles.

Question 7.
Explain about condensation in detail.
Answer:
1. Meaning: The transformation of water vapour into water is called condensation. Cause: Condensation is caused by the loss of heat.

2. Sublimation: When moist air is cooled, it may reach a level when its capacity to hold water vapour ceases. Then, the excess water vapour condenses into liquid form. If it directly condenses into solid form, it is known as sublimation.

3. Process: In free air, condensation results from cooling around very small particles termed as hygroscopic condensation nuclei. Particles of dust, smoke and salt from the ocean are particularly good nuclei because they absorb water. Condensation also takes place when the moist air comes in contact with some colder object and it may also take place when the temperature is close to the dew point. Condensation, therefore, depends upon the amount of cooling and the relative humidity of the air.

Factors affecting condensation:

• When the temperature of the air is reduced to dew point with its volume remaining constant;
• When both the volume and the temperature are reduced;
• When moisture is added to the air through evaporation.

However, the most favourable condition for condensation is the decrease in air temperature. After condensation the water vapour or the moisture in the atmosphere takes form of dew, frost, fog and clouds.

Question 8.
Explain about fog and mist.
Answer:
When the temperature of an air mass containing a large quantity of water vapour falls all of a sudden, condensation takes place within itself on fine dust particles. So, the fog is a cloud with its base at or very near to the ground.

• Because of the fog and mist, the visibility becomes poor to zero. In urban and industrial centres smoke provides plenty of nuclei which help in the formation of fog and mist.
• Such a condition when fog is mixed with smoke, is described as smog.
• The only difference between the mist and fog is that mist contains more moisture than the fog.
• In mist each nuceli contains a thicker layer of moisture. Mists are frequent over mountains as the warm air rises up the slopes and meets a cold surface.
• Fogs are drier than mist and they are prevalent where warm currents of air come in contact with cold currents. Fogs are mini clouds in which condensation takes place around nuclei provided by the dust, smoke, and the salt particles.

Question 9.
On the basis of rainfall received, in how many groups can we classify the world?
Answer:
On the basis of rainfall received, we can classify the world into five groups.

1. The equatorial belt, the windward slopes of the mountains along the western coasts in the cool temperate zone and the coastal areas of the monsoon land receive heavy rainfall of over 200 cm per annum.
2. Interior continental areas receive moderate rainfall varying from 100 – 200 cm per annum.
3. The coastal areas of the continents receive moderate amount of rainfall.
4. The central parts of the tropical land and the eastern and interior parts of the temperate lands receive rainfall varying between 50-100 cm per annum.
5. Areas lying in the rain shadow zone of the interior of the continents and high latitudes receive very low rainfall-less than 50 cm per annum.

Question 10.
Use a diagram to explain the process of evaporation.
Answer:
Evaporation is a process by which water is transformed from liquid to gaseous state. Heat is the main cause for evaporation. Movement of air replaces the saturated layer with the unsaturated layer. Hence, the greater the movement of air, the greater is the evaporation.

In This Post we are  providing  CHAPTER 8 COMPOSITION AND STRUCTURE OF ATMOSPHERE NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON COMPOSITION AND STRUCTURE OF ATMOSPHERE

Question 1.
Why are the vapour and dust particles important variables of weather and climate?
Answer:
The water vapour and dust particles are important variables of weather and climate because they are the source of all forms of condensation and principal absorbers of heat received from the sun or radiated from the earth. Besides, they affect the stability of the atmosphere.

Question 2.
What is meant by a normal lapse rate?
Answer:
The temperature decreases with altitude because the atmosphere is heated more by the heat radiated from the earth’s surface. Wanner air lying under the cooler air goes up or turns downward. In this layer, the temperature decreases vertically at a rate of 0.65°C per 100 metres. It is called the normal lapse rate.

Question 3.
What is homosphere?
Answer:
The atmospheric layer up to an altitude of 90 km. above the surface of the earth is generally called homosphere. It is uniform in term of these major gases – nitrogen, oxygen and argon. In addition, it also contains some rare gases like neon, krypton and xenon.

Question 4.
Name the gases and other materials which compose the atmosphere.
Answer:
Nitrogen, oxygen and argon are the most important gases of the atmosphere. In addition, it contains gases like carbon dioxide, neon, helium, ozone, hydrogen, methane, krypton and xenon. Besides, there are also present huge amounts of solid and liquid particles collectively called aerosols.

Question 5.
Discuss the properties of nitrogen gas.
Answer:
Nitrogen is the most abundant gas of the atmosphere. By volume, it constitutes 78.8% of the total gases present in the atmosphere. Nitrogen does not easily enter into chemical union with other substances but gets fixed into the soil. It serves mainly as diluent or dissolver. It regulates combustion.

Question 6.
Distinguish between troposphere and stratosphere.
Answer:

Troposphere	Stratosphere
(1) It is the lowermost layer of the atmosphere.	(1) It is the second layer of the atmosphere above the earth.
(2) Its height varies from 10-18 km. at the equator.	(2) Its height is up to 50 km.
(3) Temperature decreases at the rate of 1 °C per 165 metres in this layer.	(3) In this layer temperature is very low and fairly constant.
(4) It is the zone of convection currents of the atmosphere.	(4) It is a zone of non-convection currents of the atmosphere.
(5) Water vapour, dust particles, clouds are found in this layer.	(5) There is no water vapour but dust particles and clouds are found.
(6) Atmospheric processes occur in this layer.	(6) This zone is free from atmospheric disturbances.

Question 7.
What is the difference between condensation and precipitation?
Answer:
Condensation is the physical process of the transition of a substance from the vapour to the liquid state, e.g., as a result of cooling or increase of pressure. It occurs in the atmosphere when the air is saturated or when it is cool. Thus, the change of state of the moisture from invisible water vapour to visible liquid (water) or solid (ice or snow ) state is known n as condensation. It is opposite of evaporation.

Precipitation, on the other hand, means ‘throwing down of moisture’. Continuous condensation in the body of the air helps the water droplets to grow in size so that the resistance of the air fails to keep them suspended. In such cases, only an ascending air current can keep them floating in the air. In the absence of such a current, the products of condensation begin to fall on the earth’s surface. The process whereby the water vapour first condenses in the air and then falls on to the earth is called precipitation.

Question 8.
Discuss the principal elements of weather and climate and the major climatic controls.
Answer:
The principal elements of weather and climate are temperature precipitation, moisture, pressure and winds. These are called elements because they are the ingredients out of which various weather and climate types are compounded. The temperature and precipitation are the main basic elements to which pressure, winds and other elements are related.

Temperature expresses the intensity of heat. Practically all the heat energy on the earth is the result of insulation or the increasing solar radiation. Unequal distribution of temperature over the earth’s surface causes differences in atmospheric pressure, which causes winds.

Higher the temperature, the greater is the capacity’ of air to hold moisture on cooling. The air is not able to retain all the moisture it gathers while warm. This leads to condensation and precipitation.

Thus, the temperature is the basic element on which other elements of climate depend.

The climatic controls are :
Latitude (or sun), distribution of land and water, the great semi¬permanent high and low-pressure belts, winds, altitude, mountain barriers, ocean currents and storms of various kinds.

Question 9.
Define the atmosphere. Explain its importance to human life.
Answer:
The atmosphere is a mixture of air and various gases which envelopes the earth all around. It represents the gaseous realm of the earth. It is held to the earth by the force of gravity.

Importance of atmosphere:

1. It contains gases like oxygen (essential for breathing) for man and animals and carbon dioxide for plants.
2. By trapping the heat, it acts as a greenhouse. It keeps the earth
   warm.
3. One of its layer, the ionosphere, reflects radio waves back to the earth and makes radio communication possible.
4. It protects us from the deadly cosmic rays and meteors which are continuously showered on the earth from outer space.
5. All the weather phenomenon take place in the atmosphere. Presence of water vapour in the atmosphere brings many changes such as condensation and precipitation. These processes influence the human life, plants and animals.
6. It absorbs ultraviolet rays.
7. It acts as an air conditioner by moderating the extremes of heat ‘ and cold.
8. It is a storehouse of water vapour.

Question 10.
Discuss the proportion of the constituent gases of the atmosphere.
Answer:
The atmosphere is a mixture of various gases. It includes :
Nitrogen (N,), Oxygen (O,), Argon (Ar), Carbon dioxide (CO,), Neon (Ne), Helium (He), Ozone (O,), Hydrogen (H), Methane (CH4), Krypton (Kr) and Xenon (Xe).

Nitrogen (N2): It is a colourless, odourless gas, the main constituent (i.e. 78.8% by volume) of the atmosphere. It is an essential constituent of living organisms. It is an important element for plants.

Oxygen (O,): Constitutes 20.94% of the total volume of the atmosphere. It is the second most abundant gas. It is essential to plant and animal life.

Argon (Ar): It constitutes one per cent volume of the total atmosphere. It is an inert gas, does not take part in any chemical reaction.

Carbon dioxide: It constitutes a very small amount (0.03%). It is an important gas in the atmospheric process. It can absorb heat and thus allows the lower atmosphere to be warmed up by heat radiation from the sun and from the earth’s surface. Green plants in the process of photosynthesis utilise carbon dioxide from the atmosphere.

Neon (Ne): Neon is an inert gaseous element occurring in’ trivial quantities (0.0018%) in the atmosphere.

Helium (He): It exists primarily in the sun’s atmosphere. It is an inert element of the atmosphere.

Ozone (03): It is an allotropic form of oxygen (02). Its main concentration lies between 20 to 25 km. from the earth’s surface.

Hydrogen (H): It is the lightest element. It is gaseous and inflammable. It is used in many chemical processes.

In This Post we are  providing  CHAPTER 4 DISTRIBUTION OF OCEANS AND CONTINENTS NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON DISTRIBUTION OF OCEANS AND CONTINENTS

Question 1.
How do lithosphere plates behave along the transform fault?
Answer:
The lithospheric plates slide over each other, neither creating nor destructing any landmass. Instead, the. friction arising from the movement of the plates usually causes severe earthquakes and earth tremors.

Question 2.
Why do geographers focus their attention on plate boundaries?
Answer:
Geographers focus their attention on plate boundaries because each plate is a tectonic plate. It is rigid and moves as a single unit. Nearly all major tectonic activity occurs along the plate boundaries.

Question 3.
What does the term ‘supercontinent’ refer to?
Answer:
The term ’supercontinent’ refers to a single common geological landmass called Pangaea. It has been proposed that all landmasses of the world had formed from this ‘supercontinent’. Pangaea had evolved some 280 million years ago, at the end of the Carboniferous period and by mid-Jurassic age, 150 million years ago. Pangaea land split into Laurasia, the northern continent, and Gondwanaland, the southern continent. About 65 million years ago, i.e. at the end of the cretaceous, bound mainland were further broken up to give rise to several other continents such as South America, Africa, Australia, and Antarctica.

Question 4.
Discuss the causes of plate movement.
Answer:
Sub-crustal convection currents invoke the mechanism of thermal convection that acts as a driving force for the movement of plates. Hot currents rise, then cool as they reach the surface. At the same time, cool currents sink down. This convectional movement moves the crustal plates. .. Owing to current movements, the rigid plates of the lithosphere, which ‘float’ on more mobile asthenosphere, are in constant motion.

Question 5.
What is a geological time-scale?
Answer:
The chronology of the geological history’ of the earth is revealed by its rocks. Geological time scale indicates the hierarchy of time periods during which different rocks of the earth have formed.

Question 6.
What do you mean by ‘jig-saw-fit’? Describe the similarities found on the east and west coasts of the Atlantic ocean. What do they suggest?
Answer:
The ‘jig-saw-fit’ means the landmasses on the east and west coast of the Atlantic ocean can be fitted together. There are many similarities found on the two coasts :

1. The Gulf of Guinea can be fitted into Cape San-Rogue of Brazil, the shoulder of Africa can be fitted into Gulf of Mexico, Western Europe and Eastern coast of North America along with Greenland can be fitted together.
2. Gold deposits of Ghana lands are found on the east and in Brazil on the west.
3. The glacial deposits are found in all landmasses of Gondwana land.

These similarities suggest that these continents were together in the geological past.

Question 7.
Discuss the Continental Drift Theory.
Answer:
Continental Drift Theory was proposed by Alfred Wegner in 1912. He postulated that all landmasses of the world have been formed from one super-continent called Pangaea.

The supercontinent, Pangaea, had evolved some 280 million years ago, at the end of the Carboniferous period and by the mid-Jurrasic age, 150 million years ago. Pangaea had split into a northern continent, Laurasia, and a southern continent Gondwanaland. About 65 million years ago, i.e., at the end of the Cretaceous, Gondwanaland further broke up to give rise to several other continents, such as South America, Africa, Australia, and Antarctica. Thus, the present distribution of the continental masses and the oceans are the n .uit of fragmentation of one or more pre-existing masses. These landmasses have drifted apart the intervening hollows having been occupied by the oceans.

There are several pieces of evidence that suggest the existence of Pangaea. This evidence is available in the form of geological watching, palaeoclimatic units, and paleomagnetism.

Question 8.
Describe sea-floor spreading in brief.
Answer:
The present distribution of continents has taken place in the last 65 million years. The drift of continents still continues. The ridges down the middle of ocean floors have been emitting lava continuously. Those mid-oceanic ridges are cracks on the floor of the ocean where molten rocks push up to form a new crust. The crust spreads among the ridge and the ocean basin widens. This phenomenon is known as sea-floor spreading. The Atlantic ocean is getting smaller and the Red Sea is the part of a crack in the crust that will widen to produce new ocean millions of years ahead in the future. In the past, the widening of the South Atlantic ocean has separated Africa and South America.

Question 9.
Explain the plate tectonic theory and its mechanism.
Answer:
Plate tectonic theory proves that the earth’s crust consists of several plates that carry continents and the ocean floors and float on the asthenosphere, moving very slowly, the movement probably resulting from currents in the asthenosphere. As shown in fig., the lithosphere is broken into seven major plates. They include :

1. Pacific plate
2. Eurasian plate
3. Indo-Australian plate
4. African plate
5. North American plate
6. South American plate
7. Antarctic plate

The latest among these is the Pacific plate which is composed of oceanic crust almost entirely. The other plates have both continental and ocean crust. No plate consists of only continental crust. Plates range in thickness from about 70 km. beneath oceans to 150 km. under continents. Each tectonic plate is rigid and moves on a single unit. Nearly all major tectonic activities occur along the plate boundaries.

Based on the relative motion of plates, three kinds of plate boundaries have been recognized. They are :
1. Zones of divergence: These are boundaries along which plates separate and in the process of separation molten materials upwell. This is commonly observed along linear ocean edge where the new lithosphere is created in the form of new ocean floors. Active volcanism and shallow focus earthquakes make such boundaries,

2. Zones of convergence: There are the boundaries along which, the edge of one plate overrides the other. The overridden plate slips down into the mantle and is absorbed. This process is known as subduction.

3. Fracture zones or Transform faults: The plates slide past each other effect creating or destructing the boundaries. However, shallow focus earthquakes may result due to this friction.

Question 10.
Describe the main features of the Indian plate.
Answer:
Indian ocean floor presents striking topography consisting of a number of elevated ridges and plateaus. Two of the ocean ridges, namely, the Mascarene Plateau, Chagos-Maldweep-Lakshadweep island ridge are said to be the volcanic tracts of two hot spots. The Northward extension of Ninety-east Ridge indeed in the trench which consumed the seafloor to the north of the Indian continental mass. The Chagos- Lakshadweep ridge linked the ancient Carlsberg ridge with the Southeast Indian ridge during the Eocene period (50 million years ago).

Consequent to the Carlsberg-Southeast Indian ocean ridge, the collision between the Indian plate and the Eurasian plate took place north of the Indian plate giving rise to the Himalayas. The suture between Indian and Eurasian plates in the Himalayan region has been along the Indus and Brahmaputra rivers.

In This Post we are  providing  CHAPTER 7 LANDFORMS AND THEIR EVOLUTION NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON LANDFORMS AND THEIR EVOLUTION

Question 1.
How does wind forms geomorphic landforms or how does wind performs its tasks in the desert areas.
Answer:

• Wind move along the desert floors with great speed and the obstructions in their path create turbulence. Wind causes deflations, abrasion and impact.
• Deflation includes lifting and removal of dust and smaller particles from the surface of rocks. In the transportation process sand and silt act as effective tools to abrade the land surface. The impact is simply sheer force of momentum which occurs when sand is blown into or against a rock surface.

Question 2.
Explain the depositional landforms formed by glaciers.
Answer:
The depositional landforms formed by glaciers are:

• Moraines: When valley glaciers retreating rapidly leave an irregular sheet of till over their valley floor. Such deposits varying greatly in thickness and in surface topography are called Moraines
• Esker: When glaciers melt, the water flows on the surface of the ice or seeps down along the margins or even moves through the holes in the ice. Very minor coarse materials settle in valley of ice beneath the glacier and when ice melts it can be found as sinuous ridge called Esker.
• Drumlins: Drumlins are smooth oral shaped ridge-like features composed mainly of glacial till with some masses of gravel and sand.

Question 3.
What are Moraines? Explain different types of Moraines with diagram.
Answer:
Moraines are long ridges of deposits of glacial till.
Different types of moraines are:

•  The lateral moraines: They form along the sides parallel to glacial valleys. These moraines partly or fully owe their origin to glacio- fluvial waters pushing up materials to the sides of glaciers.
• Ground moraines: Many valley glaciers retreating rapidly leave an irregular sheet of till over their valley floors. Such deposits varying greatly in thickness and in surface topography are called Ground moraines.
• Medial moraines: The moraines in the centre of the glacial valley flanked by lateral moraines is called medial moraines.

Question 4.
Differentiate between:
1. Stalactites and Stalagmites
2. Sinkholes and Urallas
3. Gorge and Canyon
Answer:
1. Stalactites and Stalagmites

S.No.	Stalactites	Stalagmites
1.	Stalactites hang as icicles of different diameters.	Stalagmites rise up from the floor of the caves.
2.	They are broad at their bases and taper towards the free ends showing up in a variety of forms.	It may take the shape of a disc, a column with either a smooth, rounded bulging end.

2. Sinkholes and Urallas

Sinkholes	Urallas
A sinkholes is an opening more or less circular at the top and funnel-shaped towards the bottom.	When sink holes and dolines join together because of slumping of material along their margins the Urallas are formed.

3. Gorge and Canyon

• A gorge is a deep valley with very steep to straight sides and a canyon is characterized by steep step-like side slopes and may be as deep as a gorge.
• A gorge is almost equal in width at its top as well as its bottom. In contrast, a canyon is wider at its top than at its bottom. In fact, canyon is a variant of gorge.
• Example, canyons commonly form in horizontal bedded sedimentary rocks and gorge form in hard rocks.

Question 5.
Explain the landforms that are seen in upper part of the river.
Answer:
In upper part of the river, many beautiful and attractive landforms are formed. Some of them are as follows:

•  V-shaped valleys: Valleys start as small and narrow rills; the rills will gradually develop into long and wide gullies; the gullies will further deepen, widen and lengthen to give rise to valleys. Depending upon dimensions and shape, many types of valleys like V-shaped valley, gorge, canyon, etc. can be recognised.
• Gorge: A gorge is a deep valley with very steep to straight sides.
• Canyon: A canyon is characterised by steep step-like side slopes and may be as deep as a gorge. A gorge is almost equal in width at its top as well as its bottom. In contrast, a canyon is wider at its top than at its bottom. In fact, a canyon is a variant of gorge.
• Waterfall: When the rivers start falling in pits in mountainous regions, it makes waterfall.
• Plunge pools: Once a small and shallow depression forms, pebbles and boulders get collected in those depressions and get rotated by flowing water and consequently the depressions grow in dimensions. A series of such depressions eventually join and the stream valley gets deepened. At the foot of waterfalls also, large potholes, quite deep and wide, form because of the sheer impact of water and rotation of boulders. Such large and deep holes at the base of waterfalls are called plunge pools.

Question 6.
Explain the landforms made by erosion caused by groundwater.
Answer:
Important landforms made by erosion are as follows:

1. Pools: These are conical shaped pits whose depth is three to nine metres. The width of the mouth is more than one metre. Due to solubility in water, when cracks in limestone increase, then pools take birth.

2.Swallow holes: Small to medium sized round to sub-rounded shallow depressions called swallow holes form on the surface of limestones through soil.

3. Sinkholes: A sinkhole is an opening more or less circular at the top and funnel -shaped towards the bottom with sizes varying in area from a few square metre to a hectare and with depth from a less than half a metre to thirty metres or more.

4. Uvalas: When sinkholes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long, narrow to wide trenches called uvalas are formed.

5. Collapse sinks: If the bottom of the sinkholes forms the roof of a void or cave underground it might collapse leaving a large hole opening into a cave or a collapse sinks.

6. Lapies: Gradually, most of the surface of the limestone is eaten away by these pits and trenches, leaving it extremely irregular with a maze of points, grooves and ridges or lapies. Especially, these
ridges or lapies form due to differential solution activity along parallel to sub¬parallel joints. The lapie field may eventually turn into somewhat smooth limestone pavements.

7. Caves: In areas where there are alternating beds of rocks (shales, sandstones, quartzites) with limestones or dolomites in between or in areas where limestones are dense, massive and occurring as thick beds, cave formation is prominent. Water percolates down either through the materials or through cracks and joints and moves horizontally along bedding planes. It is along these bedding planes that the limestone dissolves and long and narrow to wide gaps called caves result. There can be a maze of caves at different elevations depending upon the limestone beds and intervening rocks. Caves normally have an opening through which cave streams are discharged. Caves having openings at both the ends are called tunnels.

Question 7.
Explain the depositional landforms made by rivers.
Answer:
Depositional Landfoi, made by rivers:

1. Alluvial Fans: Alluvia ms are formed when streams flowing from higher levels break into foot slope plains of low gradient. Normally very coarse load is carried by streams flowing over mountain slopes. This load becomes too heavy for the streams to be carried over gentler gradients and gets dumped and spread as a broad low to high cone shaped deposit called alluvial fan. Usually, the streams which flow over fans are not confined to their original channels for long and shift their position across the fan forming many channels called distributaries. Alluvial fans in humid areas show normally low cones with gentle slope from head to toe.

2. Deltas: Delta is like alluvial fans but develop at a different location. The load carried by the rivers is dumped and spread into the sea. If this load is not carried away far into the sea or distributed along the coast, it spreads and accumulates. Such areas over flood plains built up by abandoned or cut-off channels contain coarse deposits. The flood deposits of spilled waters carry relatively finer materials like silt and clay. The flood plains in a delta are called delta plains.

3. Floodplains: Floodplain is a major landform of river deposition. Large sized materials are deposited first when stream channel breaks into a gentle slope. Thus, normally, fine sized materials like sand, silt and clay are carried by relatively slow moving waters in gentler channels usually found in the plains and deposited over the bed and when the waters spill over the banks during flooding above the bed.

4. Natural Levees: Natural levees are found along the banks of large rivers. They are low, linear and parallel ridges of coarse deposits along the banks of rivers, quite often cut into individual mounds. During flooding as the water spills over the bank, the velocity of the water comes down and large sized and high specific gravity materials get dumped in the immediate vicinity of the bank as ridges. They are high nearer the banks and slope gently away from the river. The levee deposits are coarser than the deposits spread by flood waters away from the river. When rivers shift laterally, a series of natural levees can form.

5. Point Bars: Point bars are also known as meander bars. They are found on the convex side of meanders of large rivers and are sediments deposited in a linear fashion by flowing waters along the bank. They are almost uniform in profile and in width and contain mixed sizes of sediments. If there more than one ridge, narrow and elongated depressions are found in between the point bars.

Question 8.
Explain the erosional landforms created by waves and currents.
Answer:
Cliffs, Terraces, Caves and Stacks are important landforms created by erosion caused by waves and currents.

• Wave-cut cliffs: Almost all sea cliffs are steep and may range from a few m to 30 m or even more. At the foot of such cliffs there may be a flat or gently sloping platform covered by rock debris derived from the sea cliff behind. Such platforms occurring at elevations above the average height of waves is called a wave-cut terrace.
• Terraces: The lashing of waves against the base of the cliff and the rock debris that gets smashed against the cliff along with lashing waves create hollows and these hollows get widened and deepened to form sea caves. The roofs of caves collapse and the sea cliffs recede further inland.
• Sea stacks: Retreat of the cliff may leave some remnants of rock standing isolated as small islands just off the shore. Such resistant masses of rock, originally parts of a cliff or hill are called sea stacks.

Like all other features, sea stacks are also temporary and eventually coastal hills and cliffs will disappear because of wave erosion giving rise to narrow coastal plains, and with onrush of deposits from over the land behind m ay get covered up by alluvium or may get covered up by shingle or sand to form a wide beach.

Question 9.
Explain the different stages of a river.
Answer:
A river passes through three stages like a human being: youth, mature and old.

1. Youth Stage: Youth streams are less in number. In this stage with poor integration and flow over original slopes showing shallow V-shaped valleys with no floodplains or with very narrow floodplains along trunk streams. Streams divides are broad and flat with marshes, swrnmp and lakes. If meanders are present, they develop over these broad upland surfaces. These meanders may eventually entrench themselves into the uplands. Waterfalls and rapids may exist where local hard rock bodies are exposed.

2. Mature Stage: During this stage streams are plenty with good integration. The valleys are still V-shaped but deep; trunk streams are broad enough to have wider floodplains within which streams may flow in meanders confined within the valley. The flat and broad inter stream areas and swamps and marshes of youth disappear and the stream divides turn sharp. Waterfalls and rapids disappear.

3. Old Stage: Smaller tributaries during old age are few with gentle gradients. Streams meander freely over vast floodplains showing natural levees, oxbow lakes, etc. Divides are broad and flat with lakes, swamps and marshes. Most of the landscape is at or slightly above sea level.

Question 10.
Distinguish between river alluvial plains and glacial outwash plains.
Answer:
River Alluvial Plains: The alluvial plain is an erosional plain that occurs from weathering caused by water currents in the sea, river or stream. Fluvial (water) movement comes from higher land regions and wear away landmasses to produce low relief plains. This is known as the alluvial plain. These landforms are made up of the deposition of sediment over a long period of time from the fluvial movement to form alluvial soil.

An alluvial plain is characterized by its relatively flat -and gently sloping landform and is normally formed at the base of a range of hills. Continuous fluvial weathering of these hills is what causes sediments to move and spread across lower levels to produce this type of plain. These plains are formed mostly by slow running rivers, as slower fluvial movement picks up less sediment off the river floor causing more particles to settle and develop into an alluvial plain. Areas where more particles are dropped off are sometimes referred to as flood plains, and the particles that settle are called alluvium.

Glacial Outwash Deposits: The large quantities of water that flowed from the melting ice deposited is called glacial outwash. Outwash plains made up of outwash deposits are characteristically flat and consist of layers of sand and other fine sediments. Such plains with their sandy soils are often used for specialized kinds of agriculture, such as the potato production in Montcalm County.

As the margins of the ice lobes retreated, glacial meltwater and precipitation drained southward to the Gulf of Mexico because higher land or glacial ice blocked flow in other directions. Ice-marginal lakes (or proglacial lakes) form when the land in front of the ice margin slopes toward the ice, allowing meltwater to pond directly in contact with the ice.

In This Post we are  providing  CHAPTER 6 GEOMORPHIC PROCESSES NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON GEOMORPHIC PROCESSES

Question 1.
What factors have caused diastrophism?
Answer:
All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include:

• Orogenic processes: It involves mountain building through severe folding and affecting long and narrow belts of the earth’s crust;
• Epeirogenic processes: It involves uplift or warping of large parts of the earth’s crust;
• Earthquakes: It involves local relatively minor movements;
• Plate tectonics: It involves horizontal movements of crustal plates. All these processes-cause pressure, volume and temperature (PVT) changes which in turn induce metamorphism of rocks.

Question 2.
Why is the surface of the earth uneven?
Answer:
The difference in the internal forces operation from within the earth which built up the crust have been responsible for the variations in the outer surface of the crust. Due to variations in geothermal gradients and strength, the actions of endogenic forces are not uniform and hence the tectonically controlled original crystal surface is uneven.

Question 3.
What factors activate the process of mass movement?
Answer:
Following factors activate the process of mass movement.

• Removal of support from below to materials above through natural or artificial means;
• Increase in gradient and height of slopes;
• Overloading through addition of materials naturally or by artificial filling;
• Overloading due to heavy rainfall, saturation and lubrication of slope materials;
• Removal of material or load from over the original slope surfaces;
• Occurrence of earthquakes, explosions or machinery;
• Excessive natural seepage;
• Heavy drawdown of water from lakes, reservoirs and rivers leading to slow outflow of water from under the slopes or river banks;
• Indiscriminate removal of natural vegetation.

Question 4.
How does biological weathering take place?
Answer:
Biological weathering takes place by:

• Animals: Animals like rabbits, rats, termides, etc. make burrows and holes in the rocks. They consumes large quantity of soils and rocks for making their habitat and destruction of food. This loosens the rock strata and disintegration occurs.
• Vegetation: Long and teanatious roots of plants work down into cracks of rocks. The roots of shrubs and trees reach deep into them and this lodge large blocks.
• Human Activities: Mining, deforestation, indiscriminate cultivation of land and construction activities contribute to weather.

Question 5.
Write the difference between:
(i) Exogenic and endogenic forces
(ii) Orogenic movements and epeirogenic movements
(iii) Physical weathering and chemical weathering.
Answer:
(i)

S.no.	Exogenic Forces	Endogenic Forces
1.	The external forces are known as Exogenic forces.	The internal forces are known as Endogenic forces.
2.	Solar energy is the sole driving force behind all the Exogenic processes. E.g. Erosion, Flood, Mining, etc.	Gravity is the sole driving force behind all the Endogenic process. E.g. Earthquake, Volcanic Eruption, etc.

(ii)

S.no.	Orogenie Movements	Epeirogenic Movements
1.	In the process of Orogenie the crust is severely deformed into folds.	Due to Epeirogenic they may be single deformation.
2.	It is mountain building process.	It is continental building process.
3.	It affects long and narrow belt of earth’s crust.	It involves uplift or wrapping of large parts of earth’s crust.

(iii)

S.no.	Physical Weathering	Chemical Weathering
1.	Physical force disintegrates the rocks.	Rocks are decomposed by chemical changes.
2.	No chemical change occurs.	Not much physical change occurs but chemical change occurs due to air and water.
3.	More effective in dry and cold areas.	Effective in hot and hum 1 areas.
4.	Insulation, frost and pressure are the agents.	Oxidation and reduction arbonation, hydration and soil are the agents.
5.	Rocks are affected at the greater depth.	Rocks are affected on the surface only.
6.	Even the strong minerals are affected by physical weathering.	Chemical resistance minerals are not affected.

Question 6.
What are different types of mass movements?
Answer:
There are three types of mass movements: Slow Movements: Creep is one type under this category which can occur on moderately steep, soil covered slopes. Movement of materials is extremely slow and imperceptible except through extended observation. Materials involved can be soil or rock debris. Soil creep, talus creep, rock creep, rock- glacier creep etc can be identified. It also includes solifluction which involves slow downslope flowing soil mass or fine grained rock debris saturated or lubricated with water. This process is quite common in moist temperate areas where surface melting of deeply frozen ground and long continued rain respectively, occur frequently. When the upper portions get saturated and when the lower parts are impervious to water percolation, flowing occurs in the upper parts.

Rapid Movements: These movements are mostly prevalent in humid climate regions and occur over gentle to steep slopes. Movements of water- saturated clayey or silty earth materials down low angle terraces or hill slides is known as earth flow. When slopes are steeper ever the bedrock especially of soft sedimentary rocks like shale or deeply weathering igneous rock may slide downslope. With heavy rainfall, thick layers of weathered
materials get saturated with water and either slowly or rapidly flow down along definite channels. It looks like a stream of mud within a valley.

Landslides: The types of landslides.

• Slumps: The slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place.
• Debris slide: rapid rolling or sliding of earth debris without backward rotation of mass is known as Debris slide.
• Rockslide: Sliding of individual rock masses down bedding, joint or fault surface is rockslide.
• Rock fall: Rock fall is free falling of rock blocks over any steep slope keeping itself away from the slope. Rock falls occurs from the superficial layers of the rock face.

Question 7.
Explain different types of chemical weathering.
Answer:
Different types of chemical weathering includes:

1. Oxidation and Reduction: Oxidation is the effect of oxygen in air and water on the rocks. The atmospheric oxygen in rainwater unites with minerals in rocks specially with iron compounds. When oxidised minerals are placed in an environment where oxygen is absent, reduction takes place. It exists normally below water table, in area of stagnant water in more hot and humid climates.

2. Carbonation: When the carbon dioxide in atmosphere dissolves in water it form carbonic acid that affects the rocks, it is carbonation. It has acidic affect and dissolves calcium carbonates and magnesium carbonates such as gypsum, marble, limestone.

3.  Hydration: When the hydrogen of water dissolves in rocks hydration occurs. Certain minerals in rocks increase their volume and become heavy when observe water contains hydrogen. They break due to its increased pressure and the colour also changes.

4. Solution: Rainwater is able to dissolve certain minerals and leaching of the soil occurs. Normally solids are also removed during leaching. For e.g.: gypsum, rock salt, etc. undergo solution.

Question 8.
Explain different types of physical weathering.
Answer:
Different types of physical weathering includes:

• Exfoliation: Due to differential heating and resulting expansion and contraction of surface layers and their subsequent exfoliation from the surface results in smooth rounded surfaces in rocks. In rocks like granites, smooth surfaced and rounded small to big boulders called tors form due to such exfoliation.
• Frost: It is an active agent in cold climatic regions in high altitudes and the cracks are filled with water during the day time, this water is frozen at night when temperature falls below freezing point.
• Pressure: Many igneous and metamorphic rocks crystallize deep in the interior under the combine influence of high pressure and temperature. The salt near surface pores cause splitting of the grains within the rocks which eventually falls off, this result into granules disintegration.

Question 9.
Explain about erosion and deposition.
Answer:
Erosion involves acquisition and transportation of rock debris. When massive rocks break into smaller fragments through weathering and any other process, erosional geomorphic agents like running water, groundwater, glaciers, wind and waves remove and transport it to other places depending upon the dynamics of each of these agents. Abrasion by rock debris carried by these geomorphic agents also aids greatly in erosion. By erosion, relief degrades, i.e., the landscape is worn down. Weathering aids erosion it is not a pre-condition for erosion to take place. Weathering, mass-wasting and erosion are degradational processes. It erosion that is largely responsible for continuous changes that the earth’s surface is undergoing. The erosion and transportation of earth materials is brought about by wind, running water, glaciers, waves and ground water.

Deposition is a consequence of erosion. The erosional agents loose their velocity and hence energy on gentler slopes and the materials carried by them start to settle themselves. In other words, deposition is not actually the work of any agent. The coarser materials get deposited first and finer ones later. By deposition depressions get filled up. The same erosional agents viz., running water, glaciers, wind, waves and groundwater act as aggradational or depositional agents also. What happens to the surface of the earth due to erosion and deposition is elaborated in the next chapter on landforms and their evolution. There is a shift of materials in mass movements as well as in erosion from one place to the other.

Question 10.
Is it essential to distinguish between geomorphic agents and geomorphic processes? If yes, explain the difference.
Answer:
Yes, it is essential to distinguish between geomorphic agents and geomorphic processes because former is the cause and latter is the stepwise process.

• Geomorphic agent: An agent is a mobile medium (like running water, moving ice masses, wind, waves and currents, etc.) which removes, transports and deposits earth materials. Running water, groundwater, glaciers, wind, waves and currents, etc., can be called geomorphic agents.
• Geomorphic Processes: The Endogenic and Exogenic forces causing physical stresses and chemical actions on earth material and bringing about changes in the configuration of the surface of the earth is known as Geomorphic Process.

In This Post we are  providing  CHAPTER 5 MINERALS AND ROCKS NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON MINERALS AND ROCKS

Question 1.
What is lithification?
Answer:
The fragments of the rocks are transported by various exogenous agencies and deposited. These deposits through compaction and/or cementation turn into rocks. This process is called lithification. In many sedimentary rocks, the layers of deposits. retain their characteristics even after lithification.

Question 2.
How would you classify the igneous rocks based on the size and nature of crystals?
Answer:
There are five types of igneous rocks based on the size and nature of crystals viz.

1. rocks with phaneritic textured crystals
2. rocks with orphan textured crystals
3. equigranular textured rocks, and
4. porphyritic textured rocks.

The crystals large enough to be seen with naked eyes or with the help of hand lens are called phaneritic textured crystals, whereas those too small to be distinguished without the aid of a microscope are – called orphan textured crystals of the igneous rocks. Where crystals in the rocks are all within the same size range, the texture is described as equigranular, whereas few large crystals are embedded in a matrix of smaller crystals, the texture is porphyritic.

Question 3.
Discuss the classification of sedimentary rocks into clastic and non-clastic division.
Answer:
Clastic means ‘broken’, describes clastic sediments consisting of particles removed individually from a parent rock source. The naming of clastic rocks depends on the size of component mineral grains.

The non-clastic sedimentary rocks are made of sediments of two basic types: chemical precipitates and organically derived sediments.

The chemical precipitates are solid mineral matters precipitated from an aqueous solution. The rock salt and gypsum are its examples. The organically derived sediments consist of remains of plants and animals as well as mineral matters produced by activities of plants and animals. Coal and limestone are examples.

Question 4.
What are schists?
Answer:
As metamorphism continues a large percentage of the minerals assume the plate-like shape and are assembled in parallel orientation in the rock, a structure is known as foliation. Strongly developed foliation is known as schist.

Question 5.
What is meant by mineral hardness?
Answer:
The degree to which a mineral surface resists being scratched is known as its mineral hardness. Hardness is important because it determines how a mineral is worn away by the abrasive action of stream, waves, wind and glaciers in the processes of erosion and transportation..

Question 6.
Write short notes on:
1. Sedimentary rocks
2. Types of metamorphism
Answer:
1. Sedimentary rocks: Exogenous agencies such as rain, wind, ice, running water, plants and animals are constantly hurried in rock disintegration producing loose and broken rock fragments in all sizes. These minerals are carried by wind, ice and running water in depressions such as lakes and seas on the earth’s surface. Such dropped materials are called sediments. Accumulation of these sediments in course of time gives rise to sedimentary rocks. The word ‘sedimentary’ is derived from the Latin word ‘sedimented’ means setting down. The sediments are usually deposited in distinct layers or strata. Therefore, these rocks are also known as stratified rocks.

2. Types of metamorphism: Metamorphism is the process of transformation of pre-existing rock into a new rock. Thus, metamorphic rocks are found when a rock is subjected to heat and/or pressure. Their characteristics are altered by forming new mineral forms. There are three types of metamorphism, viz. foliation, lineation and banding. When, under continued metamorphism, its minerals assume the plate-like shape and are assembled in parallel orientation in the rock, it is called foliation, e.g., Schist is formed in this manner.

When the mineral grains are drawn out into long, thin, pencil-like objects, all in parallel alignment, it is referred to as lineation. In another type of metamorphism, i.e., banding, the minerals of different varieties or groups are segregated into alternate layers. These layers are usually of light or dark shades, making the banding conspicuous.

Question 7.
What is the economic importance of minerals?
Answer:
Mineral resources can be divided into four main groups – essential resources, energy resources, metal resources and industrial resources. The most basic group, essential resources, comprises soil and water. Energy resources can be divided into fossil fuels (crude oil, natural gas, coal, oil shale and tar sand) and nuclear fuels (uranium, thorium and geothermal power). Metal resources range from structural metals such as iron, aluminium and titanium to ornamental and industrial metals such as gold, platinum and gallium.

Mineral deposits have two geological characteristics that make them a real challenge to modem civilization. First, all of them are non-renewable resources. The geological processes that form them are much slower than the rate at which we exploit them. There is no likelihood of our ability to grow mineral deposits at a rate equal to our consumption. Second, mineral deposits have a place value. We cannot decide from where to extract them; nature made that decision for us when the deposits were formed.

Question 8.
Describe the categorization of metamorphic rocks.
Answer:
The metamorphic rocks can be broadly grouped into two major classes – cataclastic rocks and recrystallised rocks. Cataclastic rocks are formed by mechanical disruption (breaking and crushing) of the original materials. The process is described as dynamic metamorphism.

The recrystallised rocks are further divided into two sub-classes – contact and regional metamorphic rocks. The contact metamorphic rocks are formed by recrystallisation under high temperature caused by intruding magma. The rocks are not subjected to bending or breaking and new minerals emanating from magma are added to metamorphosed rocks. The regional metamorphic rocks undergo recrystallisation during the process of being deformed by sharing often under the condition of high pressure or high temperature or bolts.

Question 9.
Discuss various types of rocks in detail.
Answer:
There are three main groups of rocks: igneous, sedimentary and metamorphic rocks.
Igneous rocks: These are formed from lava hurled out of a volcano or from the cooling of hot magma below the crust. Granite is a coarse-grained rock that was formed by the slow cooling of magma. Basalt is a fine-grained igneous rock, almost black, that was formed by quick cooling of lava. Chemical differentiation of magma gives rise to mafic and felsic types of igneous rocks.

The size of mineral crystals in an igneous rock largely depends upon the rate of cooling of magma. As a general rule, rapid cooling results in small crystals and slow cooling in large crystals. Extremely sudden cooling results in the formation of a natural glass which is non-crystalline. Large bodies of magma trapped beneath the surface cool very slowly because the surrounding rocks conduct the heat slowly. Rapid cooling occurs in lava that loses heat rapidly to the atmosphere or to the overlying ocean water.

Question 10.
Describe the formation of igneous rocks, giving suitable examples of various types.
Answer:
The igneous rocks are divided into extrusive rocks and intrusive rocks. When the magma solidifies on the surface of the earth, we call it an extrusive rock. A typical example of this kind of rock is basalt. It is a very fine-grained rock, usually Sf black in colour.

On the other hand, when the magma solidifies in the crust, below the surface, it is called an intrusive rock. The few most common examples of intrusive rocks are granite and dolerite. More frequent, however, is the solidification of magma below the earth’s surface leading to the formation of intrusive rocks. Igneous rocks are classified on the basis of chemical composition and texture. Chemical differentiation of magma gives rise to mafic and felsic types of igneous rocks.

Texture relates to the sizes and pattern of the mineral crystals present in the rock. The size of mineral crystals in an igneous rock depends largely upon the rate of cooling of magma. As a general rule, rapid cooling results in small crystals and slow cooling results in large crystals. Extremely sudden cooling results in the formation of natural glass which is non-crystalline. Large bodies of magma trapped beneath the surface cool very slowly because the surrounding rocks conduct the heat slowly. Rapid cooling occurs in lava that loses heat rapidly to the atmosphere or to the overlying ocean water.

In This Post we are  providing  CHAPTER 3 INTERIOR OF EARTH NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON INTERIOR OF EARTH

Question 1.
How do the rocks of the earth’s mantle behave when subjected to the earthquake waves?
Answer:
The earth’s mantle behaves as an elastic solid when subjected to the earthquake waves. It changes the shape of the landscape when stresses are applied, but returns exactly to its original shape when these stresses are removed.

Question 2.
What is asthenosphere?
Answer:
The asthenosphere is the zone of hot rocks, believed to be in a plastic condition, underlying the solid lithosphere or the earth’s crust. It is sometimes termed as the soft layer of mantle or the low-velocity zone because the earthquake waves travel in it at reduced velocities.

Question 3.
Distinguish between Body waves and surface waves.
Answer:
The earthquake waves which travel longitudinally through the solid body of the earth are called Body waves. They move-faster. Those waves which move transversally along the surface are known as Surface waves. They move slowly and cause more disaster.

Question 4.
Define surface waves along with their sub-types.
Answer:
The earthquake waves which move along the free upper crust of the earth are called surface waves. Surface waves are of two types, viz, Rayleigh waves and Love waves. Rayleigh waves can be visualised as water waves travelling across the surface of a still pond after a pebble has been tossed into the water. But the motion in the Love waves is entirely horizontal, at right, angles to the direction of the wave motion. The Rayleigh and Love waves travel more or less the same length, but with different speeds.

Question 5.
Describe the three types of earthquake waves.
Answer:
These waves are :

1. ‘P’waves or longitudinal waves-These are also known as primary waves. These travel in the direction of their movement. They can travel through solids as well as liquid and gaseous matter.
2. ‘S’ waves or transverse waves – These are also known
   as secondary waves. These travel at a right angle to the direction of their oscillation. They can travel in solid ‘? medium only.
3. ‘L’ waves – These are known as surface waves. These waves do hot go deep into the earth.

Question 6.
Write short notes on :
1. Shadow zone
2. The earth’s crust
Answer:
1. Shadow zone – It lies beneath the surface of the earth, i.e., in its interior. The seismic waves bend as they travel through the core and, therefore, ‘P’ waves are not directly received in a zone known as the shadow zone. Also, ‘S’ waves are not received there because they do not travel through the liquid outer core. Only surface waves are received in the shadow zone.

2. The earth’s crust – This is also known as the lithosphere. The crust is the outermost shell 1 of the earth. It consists of the surface granite SIAL and the intermediate basic SIMA layers. It is separated from the under layer MANTLE by the Mohorovicic Discontinuity. There are two kinds of crust – continental and oceanic. Continental crust has an average density of 3 g/cnt3, the average thickness of 35 to 40 km. (22 to 25 miles) with large areas older than 1500 million years. Continental crust is a complicated structure and has a variable composition. Oceanic crust is thinner than continental crust. Its average density is 2.7 g/cm3 and average thickness of only 6 km. (3.7 miles), with the simple layered structure of the uniform composition.

Question 7.
Discuss how do seismic waves suggest layering of the earth’s interior.
Answer:
Seismic waves are the earthquake waves. The movement of seismic waves tells us a great deal about the earth’s internal structure. The shock waves arising from earthquakes pass through the interior of the earth in different ways and provide evidence about the inaccessible interior region of the earth. Seismic waves are of two types -: body waves and surface waves. Body waves travel through the solid body of the earth, whereas surface waves move along the free upper crust of the earth. Surface waves, in turn, are of two types, viz, Rayleigh waves and Love waves.

Body waves also have two sub-types, viz, ‘P’ waves and ‘S’ waves. ‘P’ (primary waves) pass through all the medium solid, liquid and gaseous, whereas ‘S’ or secondary waves do not pass through liquids.

Based on the above observation related to seismic waves, the interior has been divided into three layers – core, mantle and crust.

The core is the innermost or central layer, the crust is the outermost layer, whereas mantle lies in the middle. Since ‘S’ waves cannot pass through the central part of the earth or core, it suggests that this part is made up of a medium which is not solid. This proves that the earth’s outer core is in a liquid state in contrast to the surrounding mantle which is solid.

The ‘P’ waves make an abrupt drop in velocity at the mantle-core _ boundary, whereas ‘S’ waves terminate here. Based on the behaviour of seismic waves, the mantle is sub-divided into two major parts – the upper mantle and the lower mantle.

The crust is distinguished from the mantle by the presence of an abrupt change in velocity of seismic waves. The change in rigidity, in turn, is due to change in the universal composition or in the physical state of the rocks.

Question 8.
Describe the earth’s mantle.
Answer:
The mantle is that part of the earth’s interior which lies between the core and the crust. It consists of solid ultrabasic rocks. The mantle is about 2900 km thick with a density of about (3.0 to 3.4) g/cm3. The lower surface of the mantle forces Gutenberg Discontinuity, the uppermost layer forces the Asthenosphere.

The ‘P’ or primary earthquake waves make an abrupt drop in velocity at the mantle-core boundary, whereas ‘S’ or secondary waves terminate at this boundary. . It is because of the presence of a plane of the discontinuous surface between the core and the mantle known as Gutenberg Discontinuity.

Based on the behaviour of seismic waves, the mantle is sub-divided into two major parts – the upper mantle and the lower mantle. The upper mantle extends from the crust to a depth of about 650 km. and includes 300 to 400 km wide Asthenosphere, the uppermost part of the mantle. Rocks in Asthenosphere behave as an elastic solid. This region is referred to as the low-velocity zone.

Question 9.

How do the waves of different types tell us about the changes in the nature of different layers of the earth’s interior?
Answer:
Seismic waves are the earthquake waves. The movement of seismic waves tells us a great deal about the earth’s internal structure. The shock waves arising from earthquakes pass through the interior of the earth in different ways and provide evidence about the inaccessible interior region of the earth. Seismic waves are of two types -: body waves and surface waves. Body waves travel through the solid body of the earth, whereas surface waves move along the free upper crust of the earth. Surface waves, in turn, are of two types, viz, Rayleigh waves and Love waves.

Body waves also have two sub-types, viz, ‘P’ waves and ‘S’ waves. ‘P’ (primary waves) pass through all the medium – solid, liquid and gaseous, whereas ‘S’ or secondary waves do not pass through liquids.

Based on the above observation related to seismic waves, the interior has been divided into three layers – core, mantle and crust.

The core is the innermost or central layer, the crust is the outermost layer, whereas mantle lies in the middle. Since ‘S’ waves cannot pass through the central part of the earth or core, it suggests that this part is made up of a medium which is not solid. This proves that the earth’s outer core is in a liquid state in contrast to the surrounding mantle which is solid.

The ‘P’ waves make the abrupt drop in velocity at the mantle-core boundary, whereas ‘S’ waves terminate here. Based on the behaviour of seismic waves, the mantle is sub-divided into two major parts – the upper mantle and the lower mantle.

The crust is distinguished from the mantle by the presence of an abrupt change in velocity of seismic waves. The change in rigidity, in turn, is due to change in the universal composition or in the physical state of the rocks.

The mantle is that part of the earth’s interior which lies between the core and the crust. It consists of solid ultrabasic rocks. The mantle is about 2900 km thick with a density of about (3.0 to 3.4) g/cm3. The lower surface of the mantle forces Gutenberg Discontinuity, the uppermost layer forces the Asthenosphere.

The ‘P’ or primary earthquake waves make an abrupt drop in velocity at the mantle-core boundary, whereas ‘S’ or secondary waves terminate at this boundary. . It is because of the presence of a plane of the discontinuous surface between the core and the mantle known as Gutenberg Discontinuity.

Based on the behaviour of seismic waves, the mantle is sub-divided into two major parts – the upper mantle and the lower mantle. The upper mantle extends from the crust to a depth of about 650 km. and includes 300 to 400 km wide Asthenosphere, the uppermost part of the mantle. Rocks in Asthenosphere behave as elastic solid. Th,is region is referred to as the low-velocity zone.

Question 10.
Distinguish between :
1. Body Waves and Surface Waves
2. The crust of the earth and Core of the earth
3. Gutenberg Discontinuity and Mohorovicic Discontinuity
Answer:
1. Body waves and Surface Waves :
Seismic waves are the earthquake waves. The movement of seismic waves tells us a great deal about the earth’s internal structure. The shock waves arising from earthquakes pass through the interior of the earth in different ways and provide evidence about the inaccessible interior region of the earth. Seismic waves are of two types -: body waves and surface waves. Body waves travel through the solid body of the earth, whereas surface waves move along the free upper crust of the earth. Surface waves, in turn, are of two types, viz, Rayleigh waves and Love waves.

Body waves also have two sub-types, viz, ‘P’ waves and ‘S’ waves. ‘P’ (primary waves) pass through all the medium – solid, liquid and gaseous, whereas ‘S’ or secondary waves do not pass through liquids.

Based on the above observation related to seismic waves, the interior has been divided into three layers – core, mantle and crust.

The core is the innermost or central layer, the crust is the outermost layer, whereas mantle lies in the middle. Since ‘S’ waves cannot pass through the central part of the earth or core, it suggests that this part is made up of a medium which is not solid. This proves that the earth’s outer core is in a liquid state in contrast to the surrounding mantle which is solid.

The ‘P’ waves make an abrupt drop in velocity at the mantle-core boundary, whereas ‘S’ waves terminate here. Based on the behaviour of seismic waves, the mantle is sub-divided into two major parts – the upper mantle and the lower mantle.

The crust is distinguished from the mantle by the presence of an abrupt change in velocity of seismic waves. The change in rigidity, in turn, is due to change in the universal composition or in the physical state of the rocks.

2. Crust of the earth and Core of the earth:

The crust of the Earth	The core of the Earth
l. This is the outermost layer of the earth.	1. This is the innermost layer ofof the earth.
2. The average density is 2.73g/cm3.	2. The average density is I7.2g/cm3.
3. It covers about 0.5% part of the earth.	3. It covers about 83% part of thethe earth.
4. It is made up of silica andaluminium.	4. It is made up of nickel and ferrous.

3. Gutenberg Discontinuity and Mohorovicic Discontinuity:

Gutenberg Discontinuity	Mohorovicic Discontinuity
1. It is the boundary between the mantle and the core.	1. It is the boundary between the crust arid the mantle.
2. It was observed by Beno Gutenberg in 1926.	2. It was observed by a Yugoslavian seismologist Mohorovicic in 1909.
3. The ‘P’ waves make an abrupt drop in the velocity at the mantle-core boundary, while S-waves disappear here.	3. The surface of a sudden increase in wave velocity, which separates crust above from the mantle below is Mohorovicic discontinuity.
4. This making a place at the dis-continuous surface between the core and mantle is known as Gutenberg discontinuity.

In This Post we are  providing  CHAPTER 2 THE ORIGIN AND EVOLUTION OF EARTH NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON THE ORIGIN AND EVOLUTION OF EARTH

Question 1.
What is the opinion of present day
scientists about the origin of moon?
Answer:
In 1838, Sir George Darwin suggested that initially the earth and the moon formed a single rapidly rotating body. The whole mass became a dumb-bell shaped body and eventually it broke. The material separated from the earth was formed as moon and the place became the Pacific Ocean. It is not accepted now.

The present theory is the “giant impact theory” or “big splat theory”. A large size body of Mars collided with the earth and that portion was separated from the earth. The same portion became as a moon which revolves around the earth. The moon was formed about 4.44 billion years ago.

Question 2.
What are the difference between terrestrial planet and jovian planets?
Answer:
The main differences between the two are summarized below:

• The terrestrial planets were formed in the close vicinity of the planet star where it was too warm for gases to condense solid particles. Jovian planets were formed at a quite distant location.
• The solar wind was most intense nearer the sun, so it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.
• The terrestrial planets are smaller and their lower gravity could not hold the escaping gases. Jovian planets are bigger and have high gravity.

Question 3.
Inner planets are terrestrial while outer planets are Jovian. Why?
Answer:
Inner planets are terrestrial while outer planets are Jovian because the terrestrial planets are smaller and their lower gravity could not hold the escaping gases. Jovian planets are bigger and have high gravity. Moreover, the solar wind was most intense nearer the sun, so it blew off lots of gas and dust from the terrestrial planets. The solar winds were not all that intense to cause similar removal of gases from the Jovian planets.

Question 4.
How did earth develop its different layers?
Answer:
During the formation of the moon, due to the giant impact, the earth was further heated up. It is through the process of differentiation that the earth forming material got separated into different layers. Starting from the surface to the central parts, we have layers like the crust, mantle, outer core and inner core. From the crust to the core, the density of the material increases.

Question 5.
Differentiate between inner planets and outer planets.
Answer:
The difference between inner planets and outer planets inner planets outer planets

Inner Planets	Outer Planets
1. Mercury, Venus, Earth and Mars are called Inner Planets	1. Jupiter, Saturn, Uranus, Neptune and Pluto are called Outer Planets
2. They are found between belt of asteroids and the sun	2. They are found after the belt of asteroids
3. They are also called terrestrial planets	3. They are called Jovian planets
4. Smaller in size	4. Larger in size
5. High density	5. Low density
6. Solid rocky state	6. Gaseous state
7. They are warm	7. They are cold

Question 6.
Explain how did life evolve on the earth?
Answer:
The origin of life as a kind of chemical reaction, which first generated complex organic molecules and assembled them. This assemblage was such that they could duplicate themselves converting inanimate matter into living substance. The record of life that existed on this • planet in different periods is found in rocks in the form of fossils. The microscopic structures closely related to the present form of the blue algae have been found in geological formations m uch older than some 3,000 million years. It can be assumed that life began to evolve sometime 3,800 million years ago.

Question 7.
Explain different phases of evolution of planets.
Answer:
Evolution of planets can be understood in three stages:

1. Formation of Disc; The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and a huge rotating disc of gas and dust develops around the gas core.

2. Formation of Planetesimals: In the next stage, the gas cloud starts and getting condensed and the matter around the core develops into small rounded objects. These small rounded objects by the process of collision develop into what is called planetesimals. Larger bodies start forming by collision and gravitational attraction causes the materials to stick together. Planetesimals are a large number of smaller bodies.

3. Formation of Planets: In the final stage, these large number of small planetesimals accrete to form fewer large bodies in the form of planets.

Question 8.
Explain the earliest theory associated with the origin of the earth.
Answer:
A large number of hypotheses were put forth by different philosophers and scientists regarding the origin of the earth. One of the earlier and popular arguments was by German philosopher Immanuel Kant. Mathematician Laplace revised it in 1796. It is known as Nebular Hypothesis. According to this theory there was a hot and rotating gas cloud called Nebula in the space. From Nebula there was a gradual loss of heat due to its rotation which resulted in cooling of its outer surface. This gradual cooling caused contraction in size of Nebula, but its speed increased due to angular momentum. The outer layer was separated from the remaining part of Nebula.

The centre of Nebula became ‘Sun’ and the planets were formed of the smaller units. The lighter material gases and the heavier dust particle gave the fact of inner and outer planets. In 1950, Otto Schmidt in Russia and Carl Weizasear in Germany somewhat revised the ‘nebular hypothesis’, though differing in details. They considered that the sun was surrounded by solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of a disk-shaped cloud and the planets were formed through the process of accretion.

Question 9.
Explain the modern theory associated with evolution of the earth.
Answer:
In modern theory the evolution of the earth is associated with Big Bang Theory. It was put forth by Edwin Hubble in 1920. In the beginning, all matter forming the universe existed in one place in the form of a ‘tiny ball” \yith an unimaginably- small volume infinite temperature and infinite density. At the Big Bang “tiny ball” exploded violently. This led to a huge” expansion. it is now generally? accepted that the event of big. bang took place 13.7 billion years before the present. The expansion continues even to the present day. As it grew, some energy’ was converted into matter. There was particularly rapid expansion within fractions of a second’ after the bang. Thereafter, the expansion has slowed down. Within first Big Bang event, the first atom began to form.

Within 300,000 years from the Big Bang, temperature dropped to 4,500k and gave rise to atomic matter. The universe became transparent. The expansion of universe means increase in space between the galaxies. An alternative to this was Hoyle’s concept of steady state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours argument of expanding universe.

Question 10.
Explain the collision and accretion I hypothesis associated with the evolution of the earth.
Answer:
Collision hypothesis and accretion hypothesis are described below in short.
1.  Collision Hypothesis: It was given by Sir James and Harold Jeffrey.

• According to this theory, a large nebula ’wandering in the space came very close to smaller nebula (Sun) and its huge upsurge of matter on the surface of smaller nebula. The matter was detected from the smaller nebula and on cooling condensed into planets.

2. Accretion Hypothesis: It was given by? Schmidt and Carl Weizascar.

• According to them, solar system started out as a cloud of gas and dust drifting in a space called nebula. This gaseous cloud
  exploded violently to form supernova. The exploitation left the vast spinning cloud and gases and thus to collapse under its own gravity and develop as denser core.
• The denser core became larger and hotter and began to burge. Later it developed into protostar which finally evolved as ‘infant Sun.
•  Away from its central surface, particles of dust began to clump together and converted into first smaller fragments of rocks and then becoming larger bodies which were called planetesimals which collided with one another to form rocky inner planets like Mercury, Venus, Earth and Mars and the remaining were outer planets.

In This Post we are  providing  CHAPTER 1 GEOGRAPHY AS A DISCIPLINE NCERT MOST IMPORTANT QUESTION for Class 11 GEOGRAPHY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.

NCERT MOST IMPORTANT QUESTION ON GEOGRAPHY AS A DISCIPLINE

Question 1.
What is geography?
Answer:
The word geography is a combination of two Greek words. ‘Geo’ meaning the earth and “Graphy’ meaning description. Thus, the meaning of geography could be to write about the earth including all that is upon it. Geography is the science dealing with the spatial distribution of various phenomena (physical & human & biotic) on the surface of the earth.

Question 2.
What is the relation of geography with other sciences?
Answer:
Geography draws its contents from both natural science and social science (sociology, economics, political science). It has also. contributed to them. Hence there are several interdisciplinary’ areas in; geography. For example. Geomorphology is closely linked with. Geology, Economic Geography with Economics, and Bio-geography with life sciences (Botany and Zoology).

Question 3.
What are the three features of systematic geography?
Answer:

1. It studies geographical facts in an individual manner.
2. It implies the detailed study of a single specific geographical factor.
3. It is explanatory and is largely interpretative.
4. A detailed study of agriculture is done by marking the agricultural regions of India.

Question 4.
Why did geography become a popular subject in school by the end of the eighteenth century?
Answer:
It was because it gave knowledge about the land to prospective migrants, administrators and traders. Gradually, along with the description of places and peoples, explanation for varying responses of people to the natural environment was also presented. Thus, geography emerged as the study of the dynamics of the man-environment relationship and its imprints on the earth’s surface.

Question 5.
What do you mean by Systematic geography?
Answer:
A study of a specific natural or cultural phenomenon that gives rise to certain spatial patterns on the earth’s surface is called Systematic geography. There are four branches of systematic geography :

1. Physiography
2. Biogeography
3. Human ecology
4. Geographic methods and techniques.

Question 6.
Write a short note on Spatial Information Technology (SIT).
Answer:
The last quarter of the 20th century has put geography on a new trajectory of development with SIT as the main source of information and information processing. SIT is concerned with data collection and analysis related to physical space or the surface of the earth with the help of advanced means of information technology, such as remote sensing, aerial photographs, and satellite imageries.

They have enabled geographers to develop geographic information systems (GIS), land information systems (LIS), and global positioning systems (GPS) as location decision administration and managerial tools. Geography in the 21 st century has entered a new era of spatial information technology (SIT). They are going to be used not only in answering the question of what is where and why but also in what should be where and why. They will not only be generating information for decision-making but also will be actively participating in decision-making.

Question 7.
Describe the various branches of geography.
Answer:
Today geography is the only discipline that brings all-natural and human sciences on a common platform. It is an interdisciplinary and integrative science having numerous branches :
A. Systematic geography :

1. Physiography: Studies the physical aspects of the earth’s surface, as landforms, climate, water, and soil.
2. Plant Geography: Studies the distribution of various kinds r- of forests and grasslands. Zoo-geography studies the
   distribution of animals and micro-organisms. Human ecology studies the changing human-nature relationship and its consequences on human life and living. Environmental y geography studies the quality of the living environment and
   its implications for human welfare.
3. Human Geography: Human beings interact with nature and create a great variety of cultural phenomena like villages, Ji towns, cities, countries, factories, roads, houses, etc. The study of location and distribution of all such phenomena falls under the purview of human geography.
4. Geographic methods and techniques: Field studies, cartography, quantitation geography, and spatial information system (GIS, LIS, GPS).

B. Regional Geography :

1. Regional Studies
2. Regional Planning
3. Regional Development
4. Regional Approach

Question 8.
Discuss two perspectives of study that characterized geography in the twentieth century.
Answer:
Geography in the twentieth century became a discipline that studied the earth’s surface from two perspectives systematic and regional. The former produced sub-disciplines like physiography, climate, biography, political geography, economic geography, health geography, etc., while the latter gave rise to regional geography, regional science, regional development, regional planning, area planning, etc.

The first started with systematic knowledge to arrive at regional patterns, while the second started with a region to arrive at systematic details. In both cases, humans remained a central theme i.e., the emphasis of the study being on the impact of systematic processes and regional patterns on humans and their activities.

Question 9.
How did the Indian scholars contribute to geography in the ancient period?
Answer:
Indian scholars were among those who laid the foundation of geography in the ancient period. Atharva Veda, written around the 10th century B.C., gives the details of the then known earth, its physical features, bio-geography, and human settlements. Indians went to different parts of the world to carry the message of Indian culture, particularly of Hinduism and Buddhism. The contribution of Indian astronomers and geographers was highly advanced for their times. Aryabhatta propounded the theory of heliocentric universe a century before Copernicus, and Bhaskaracharya mentioned the gravity of the earth 1200 years before Newton. Kalidas’s description of the geography of Central India in ‘Meghaduta’ is highly professional,

Question 10.
What is the importance of Physical geography?
Answer:
Physical geography includes the study of the lithosphere, atmosphere, hydrosphere, and biosphere.

• Soils are formed through the process of pedogenesis and depend. upon the parent rocks, climate, biological activity, and time. Time provides maturity to soils and helps in the development of soil profiles. Each element is important for human beings.
• Landforms provide the base on which human activities are located.
• The plains are utilized for agriculture. Plateaus provide forests and minerals. Mountains provide pastures, forests, tourist spots and are sources of rivers providing water to lowlands.
• Climate influences our house types, clothing, and food habits.
• Climate has a profound effect on vegetation, cropping pattern, livestock farming, and some industries, etc.
• Temperature and precipitation ensure the density of forests and the quality of grassland.
• Oceans are the storehouse of resources and are rich in mineral resources, fish, and other seafood.

Soils are renewable resources, which influence a number of economic activities such as agriculture.

Physical geography is fast emerging as a discipline for evaluating and managing natural resources.