Question 1

Question 3What do you understand by denudation?

Accepted Answer

Denudation is the long-term effect of processes that cause the wearing away of the earth's surface leading to a reduction in elevation and relief of landforms and landscapes. Denudation is two fold process, i.e. both destructive and constructive. It causes wearing away of rocks and then deposition of the eroded materials forming plains.

Question 2

Question 5In what ways does atmosphere assist in weathering?

Accepted Answer

Atmosphere assists in weathering due to its various elements that participate in disintegration of rocks. The factors of atmosphere that affect weathering are:Temperature - The diurnal and seasonal variation of temperature weakens the rocks and finally leads to their weathering by peeling.Air(wind) - Winds as source of weathering are more effective in arid areas. The sand particles strike the soft rocks and slowly erode them.Rain and flowing water - Water and frost are also important agents of mechanical weathering. The atmosphere contains oxides of sulphur and nitrogen that result in acid rain. Rain water dissolves some of minerals and cause chemical weathering.

Question 3

Question 6What is meant by chemical weathering?

Accepted Answer

The decomposition of rocks is called chemical weathering. It involves the breaking down of rocks by altering or dissolving the rock minerals due to chemical action or changes. It is more common in hot and humid regions. It is a slow and gradual process which occurs due to exposure to air and water. For example, the iron present in rocks reacts with oxygen and water to form rust.

Question 4

Question 7How does biological weathering take place?

Accepted Answer

Biological weathering takes place due to biotic factors like plants and animals. It takes place in following ways:The roots of plants grow into cracks and crevices in search of water and nourishment. As they grow, they exert great pressure on the rocks and break them.Sometimes the roots produce carbonic acid which changes the composition of minerals.Animals also loosen and weaken the rocks by burrowing.Human activities such as road construction, mining, farming and deforestation cause weathering and disintegration of rocks.

Question 5

Question 8What do you understand by mechanical weathering? How does it take place?

Accepted Answer

The breakdown of rocks into smaller fragments by physical processes such as frost wedging is called mechanical weathering or disintegration.The physical or mechanical weathering occurs due to factors such as the extremes of temperature, nature of rocks, structure of rocks, frost, wind and slope of land. It does not involve any chemical change in the composition of rock. It is more effective in dry regions.

Question 6

Question 9How does composition of rock affect mechanical weathering?

Accepted Answer

The rocks are of different types. They may be hard or soft, soluble or insoluble. The mechanical weathering takes place in the softer or soluble rocks more easily than in the hard and insoluble rocks. Therefore, composition of rock affects mechanical weathering.

Question 7

Question 10Name the factors responsible for chemical weathering.

Accepted Answer

The factors responsible for chemical weathering are:OxidationHydrationCarbonationSolution

Question 8

Question 11What is carbonation? Give two examples of the landforms formed by carbonation?

Accepted Answer

Carbonation is the reaction of carbonic acid on minerals. Rainwater, when mixed with carbon dioxide in the atmosphere forms a weak solution of carbonic acid. It acts on rocks containing limestone and chalk. The reaction results in calcium bicarbonate which is highly soluble and gets easily washed away in solution as it flows through the rocks or seeps below the surface.Two examples of the landforms formed by carbonation are stalactites and stalagmites.

Question 9

Question 12How does chemical weathering take place?

Accepted Answer

The decomposition of rocks is called chemical weathering. It involves the breaking down of rocks by altering or dissolving the rock minerals due to chemical action or changes. It involves processes like oxidation, hydration, carbonation and solution. It is more common in hot and humid regions. It is a slow and gradual process which occurs due to exposure to air and water.

Question 10

Question 1Observe the image given below and answer the questions that follow.Image 1Image 2Your cousin brother has sent these images to you after visiting Sahara Desert with his family. He was surprised to see the various types of sand dunes found in the desert. From your geographical point of view identify the images sent by your cousin. Also explain why they have different shape?

Accepted Answer

Image 1 depicts Barkhans.Barkhan dunes are crescent shaped with horns of crescent trailing downwards. They are caused by accumulation of sand at an obstacle by the prevailing winds, giving them convex and gentle slope at the windward side and are concave and steep at the leeward side. Hence, Barkhan dunes are formed transversely to the direction of winds.Image 2 depicts Seif dunes.These are long narrow ridges of sand, lying parallel to the direction of prevailing winds. The prevailing dominant winds blow the corridor between the lines of dunes so that they are swept clean of sand and remain smooth. Hence, Seif dunes are formed longitudinally with the direction of winds.

Question 11

Question 2Weathering and Denudation

Accepted Answer

Sl.No.WeatheringDenudation1.It is disintegration of rocks where they exist.It is wearing away of earth's surface.2.It is destructive process.It is destructive as well as constructive process.3.It is only a part of denudation.It includes weathering, erosion, mass movement and transportation.4.Weathering is a relatively short term process.It is a long term process.5.Main agents are temperature, water, wind, oxygen etc.Main agents are wind, waves, glaciers and volcanoes.

Question 12

Question 4Deposition is the main work of river in the lower course.

Accepted Answer

As the river approaches the sea or ocean, its gradient decreases, resulting in a reduction of the river's velocity. It's volume also increases due to addition of tributaries along the way. Due to this, it cannot carry the sand particles any more and deposits all the sediments at its mouth. Hence, deposition is the main work of river in the lower course.

Weathering and Denudation

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