Social Science : Geography
LITHOSPHERE – II
VII. Answer in paragraph
1. Write a note on weathering classify and explain.
• Weathering is the disintegration and decomposition of materials of the earth's crust by their exposure to atmosphere.
• Physical weathering
• Biological weathering
• Chemical weathering
• The breakdown of rocks without changing their chemical composition, through the action of physical forces is " Physical Weathering"
• Exfoliation, block disintegration, granular disintegration, are different types of weathering.
• Disintegration and decomposition of rocks due to chemical reactions is called Chemical Weathering.
• Chemical weathering takes place through oxidation, carbonation, solution and hydration.
• Due to plants, animals and human beings occur.
• Biological weathering, Penetration and expansion of plant roots.
2. Explain the erosional landforms formed by underground water.
• As an agent of gradation, underground water creates distinct landforms in limestone regions
Erosional Landforms of Underground Water
• When the rain water mixes with carbon - di - oxide and enters into a limestone region, it dissolves and destroys much of the limestone.
• Deposition of red clay soil on the surface of the Earth is due to the dissolution of limestone content in the rock, (iron oxide is the reason for redness)
• Lappies are the long furrows formed when the joints of limestone rocks they are corrugated by groundwater.
• A funnel shaped depressions formed due to dissolution of limestone is 'sinkholes'.
• The hollows that are formed by the dissolution.
• Caves are hollow that are formed by the dissolution of limestones by carbonic acid are 'caves'.
• Caverns are the caves with irregular floors. Ex. Guptadham caves in Western Bihar.
3. What is a glacier? Explain its types.
• A large mass of ice that moves slowly from its place of accumulation is a 'Glacier'.
Based on the place of occurence Glaciers are divided into
• Continental Glacier
• Valley Glacier
• Thick Sheets of ice that covers vast areas of a continent is called 'Continental Glacier'.
• The glacier which takes its origin from a snow covered mountain range is known as a 'Valley Glacier'
(Like the rivers glaciers also carry out erosion, transportation and deposition)
4. Describe the depositional work of winds.
Depositional Landforms of wind :
• Deposition occurs when the speed of wind is reduced by the presence of obstacles, (bushes, forests, rock, structures) The sediments carried by wind get deposited on both the wind ward and leeward sides of these obstacles.
• Some of the depositional landforms are
• sand dunes
• In deserts, during sand storms, wind carries loads of sand. When the speed of wind decreases, huge amount of sand gets deposited. These mounds or hills of sand are called 'sand dunes'.
• There are different types of sand dunes are
• Transverse dunes
• Longitudinal dunes
• Loess are the deposits of fine silt and porous sand over a vast region.
• Barchans are isolated, Gescent shaped sand dunes, (windward side - gentle slope; leeward side - steep slope)