Maharashtra Board Class 11 Geography Solution Chapter 2 Weathering and Mass Wasting
Balbharati Maharashtra Board Class 11 Geography Solution Chapter 2: Weathering and Mass Wasting. Marathi or English Medium Students of Class 11 get here Weathering and Mass Wasting full Exercise Solution.
Std |
Maharashtra Class 11 |
Subject |
Geography |
Chapter |
11 |
Chapter Name |
Weathering and Mass Wasting |
Q.1) Complete the chain :
Rock type | Name of the rock | Dominant type of weathering |
1) Igneous | 1) Dolomite | 1) Physical Weathering |
2) Sedimentary | 2) Slate | 2) Chemical Weathering |
3) Metamorphic | 3) Basalt | |
4) Limestone | ||
5) Granite |
Answer – the completed chain is mentioned below : –
Rock type | Name of the rock | Dominant type of weathering |
1) Igneous | Basalt | Physical Weathering
|
Granite | ||
2) Sedimentary | Dolomite | Chemical Weathering |
Limestone | ||
3)Metamorphic | Slate | Physical Weathering |
- 2) Identify the correct correlation :
A : Assertion; R : Reasoning
1) A : In areas of high rainfall, slides are very common.
R : Types of mass wasting movements are dependent on a region’s climate.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 4) Both A and R are correct but R is not the correct explanation of A.
2) A : Gravity is a major factor in mass wasting.
R : Gravity pulls all things down to the earth’s surface.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 3) Both A and R are correct and R is the correct explanation of A.
3) A : Freeze and thaw weathering is common in desert areas.
R : Water gets into cracks and breaks the rocks.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 4) Both A and R are correct but R is not the correct explanation of A.
4) A : Surface water helps solifluction
R : Water table is responsible for the same.
1) Only A is correct
2) Only R is correct
3) Both A and R are correct and R is the correct explanation of A.
4) Both A and R are correct but R is not the correct explanation of A.
Answer – 1) Only A is correct
Q 3) Identify the correct group :
A) 1) Oxidation B) 1) Solution
2) Carbonation 2) Salt Weathering
3) Freeze-thaw weathering 3) Oxidation
4) Shattering 4) Carbonation
C) 1) Fall D)1) Pressure
2) Creep 2) Temperature
3) Slide 3) Slope
4) Flow 4) Rainfall
Answer – The correct group would be
C) 1) Fall
2) Creep
3) Slope
4) Flow
4) Give geographical reasons :
1) Temperature is the main factor behind granular weathering.
Answer – In arid and semi arid areas, temperature plays a vital role in granular weathering. This is because there is quite a lot of fluctuation between the day and night temperatures.
The rocks on the surface get hotter with rising temperatures during the day time and cooler with lower night temperatures. As a result, the molecules of the several constituent minerals present within the rock react differently to this temperature fluctuating phenomenon.
Eventually, the rock disintegrate due to the difference in stress within by virtue of granular weathering, thereby breaking it into smaller fragments.
2) Human is an agent of weathering.
Answer – Anthropogenic Weathering – Human beings are biological agents of weathering. With developmental and economic activities, we humans have contributed largely to the process of weathering by accelerating it many folds.
By the economic and technological advances involving activities like mining, building roads, bridges, dams and large reservoirs for human well being, we have enhanced the process of deforestation and at the same time caused enormous air and water pollution which has largely resulted in increased rate of weathering at various places where these activities have taken place.
For instance mining, building of dams, or other such activities involves blasting hills, ridges using explosives and also requires large scale deforestation, that enhances the disintegration of rocks, thereby causing weathering.
3) Slope is a major factor in mass wasting.
Answer – Movement of a loose mixture of soil, rocks and land through a downward slope due to the effect of gravity is known as mass wasting.
As is the case with mass wasting, no medium like water, wind, rain or ice for the downward movement of material (ie large chunks of soil, rocks and land) is required, through the slope. It is purely due to the effect of gravity that this process occurs. This is continuous and slow process, most of the times, on all slopes, but sometimes it could be sudden, abrupt with disastrous and lethal consequences at times.
Heavy rainfall in areas where deforestation have occurred could accelerate mass movements and aggravate the situation, causing mud slide.
4) Oxidation changes the size and colour of the rocks.
Answer – Oxygen radicals present in air or water tends to react with some of the elements that may be present in the rocks and eventually change the colour, size and volume of the rocks. This process is called oxidation. When oxidation occurs in metals like iron, copper or aluminium forming iron oxide, copper oxides and aluminium oxides, respectively, we call it rusting of those elements.
Therefore, such elements when present in the rock minerals may be oxidised forming their respective oxides, resulting in change of size, volume and colour, since iron oxides are red, copper oxides are green and aluminium oxides are yellow.
Oxidation of the minerals within also makes the rocks vulnerable to weathering as such chemical changes makes it disintegrate at a quicker rate than otherwise.
5) Effect of mass movement will be greater along the western slope of the Sahyadris than the eastern slope.
Answer – Effects of mass movement will be considerably greater in the western slope of the Sahyadris when compared to its eastern slope mainly because of the following reasons : –
5) Write short notes on :
1) Gravity and Solifluction
Answer – Gravity is the main force responsible for mass movements, since it is the force of the earth that continuously acts on any object at any point of time pulling everything downwards.
Solifluction is the slow movement or downhill creep of soil in periglacial or alpine regions, mainly in colder climatic conditions. It occurs very slowly and its movement could be expressed in millimetres or centimetres per year. This is also due to gravity, as the overlying soil slides down slopes in cold hilly climatic conditions.
2) Role of water in mass wasting
Answer – Water is not directly involved is the mass wasting process, since this is a continuous process due to gravity occurring in the slopes. However, water plays a significant role, as it acts as a transporting medium accelerating the process.
When rainfall occurs, water makes the soil heavier which further speeds up the mass wasting process. Water can also reduce the friction below the rocks, loosens the soil, making it easier for gravity to pull down rocks, soil and cause mud slides down the slopes.
3) Exfoliation
Answer – The rocks which are present beneath the surface experience a higher pressure due to weight of the overlying rocks over them.
When these underlying rocks get exposed to the surface, once the surface rocks are removed, they are now subjected to lower pressure.
Due to this kind of pressure differences, at depth (high) and surface (low), the outer part (ranging a few centimetres to metres) of the rock mass expands outward causing the outer layer of the rock to separate from the lower layer. This type of weathering is called dislodgement which happens mainly due to pressure release or unloading ie removal of the overlying rocks. It is quite common in igneous rocks, like granite, where the rock forming material is homogeneous. This process where there is successive removal of these outer layers of the rocks is called exfoliation.
4) Weathering and homogeneity in rocks
Answer – Rocks that are on the surface, are exposed and therefore affected by the climatic conditions of that particular region. Rocks break due to the effect of heat, water, pressure, etc. in different ways. Rocks having joints or layers break easily in comparison to rocks which are homogeneous and it is also known that the sedimentary rocks are more vulnerable to break easily compared to the igneous rocks.
Weathering : Breaking of rocks results in the grains of the rock being disintegrated which means that they get weakened with time, get eroded and break. Weathering refers to the physical or chemical changes causing breakdown due to weather conditions.
Changing temperature, rainfall and chemical reactions due to oxidation etc leads to these processes. Since very little or no motion of materials takes place in the process of weathering, it is called in-situ process and it often results in rounding and smoothening of sharp edges of rocks.
5) Carbonation
Answer – Decaying and decomposition of dead organic matter – plants and animals in the soil lead to production of carbon-di-oxide, which when reacts to the minerals of rocks cause weathering.
Minerals like carbonates and feldspar gets decomposed with the effect of carbon di oxide on them. Water and humid climatic conditions adds up to the process of decomposition. Sedimentary rocks like limestones are particularly vulnerable to this kind of weathering. During the process of carbonation the minerals like calcium and carbonate in limestone gets detached from each other, thereby decomposing the sedimentary rock itself.
Q.7) Answer in detail :
1) Explain with examples the process of weathering happening in Konkan.
Answer – Konkan is situated in the western coastline of India and can be divided into the North Konkan which includes Mumbai, Thane and Raigad districts while South Konkan includes Ratnagiri and Sindhudurgh districts. The area is mainly made of laterite rocks and high altitude plateaus in Sitara, Ratnagiri and Sindhudurg districts.
The presence of soft silica matter can be prominently seen in laterite rocks, which are often washed out due to heavy rainfall in the region leaving rocks weathered and laterite soil being formed containing high concentration of iron and aluminium.
Oxygen from the air further reacts to these minerals of iron and aluminium in the laterite soil forming oxides and causing further chemical weathering.
Examples of this kind of weathering process can be seen in Matheran, Southern parts of Mahabaleshwar, around Bhima Shankar
2) Explain the correlation between Himalayas and mass movements. Give examples wherever necessary.
Answer – Mass movement is a continuous process of downward movement of soil, rocks and large chunks of land masses along the slopes in hills, mountains or plateaus due to effect of gravity. Steeper slopes enhances chances of mass movement, as does other agents like water by means of rainfall that accelerate the process by reducing friction and loosening soil.
The Himalayas have the highest mountains, peaks, hills, plateaus and passes, thereby the steepest slopes, which gives rise to glaciers, high altitude snowfall activity and origin of various rivers. Also, there is high vulnerability of earthquakes due to the tectonic plates of Eurasian and Indus plates meeting deep beneath the crust.
The steep slopes means rapid and fast moving rivers causing mass movements on a large scale. Also, rainfall is quite high especially in the north eastern region causing landslides and mass movements. Glaciers too are a source of origin of many rivers like Ganga, Yamuna, etc which move down along the mountains carrying rocks and other heavy sediments.