Exogenic Movement
Exogenic movements - These are the Earth's movement caused due to various forces from outside the Earth's surface. It involves degradation and aggradation.
Exogenic movements are caused due to Solar energy and Gravitational force.
Aggradation - It involves the action of various processes that cause deposition on the surface in order to bring uniformity of grade (slope).
Degradation (Denudation) - It is the combined action of various processes that cause the wearing away of the Earth's surface and causes a general lowering and levelling out of the surface. It involves weathering, erosion & transportation and Mass movement.
Weathering
Weathering - It is the total effect of various processes that co-operate in bringing about the decay and disintegration of rock involving no large scale transportation. Weathering is in situ and doesn't involve the transportation of degraded rock material.
Factors affecting weathering -
- Rock type and structure - It includes rock massiveness, crystal structure, presence of fractures, bedding plane, porosity, etc. For example - Sedimentary rocks are weathered faster than Igneous rocks.
- Slope and Aspect - Steep slope will greatly aid weathering as the disintegrated material will immediately flow down, also the rain water tends to run off the surface rather than percolating. The slopes which are exposed to wind, rain and sunlight are more prone to weathering.
- Temperature - The considerable range of temperature both diurnal (with in a day) and annual, subjects the surface layer to expansion and contraction. The temperature also increases the rate of chemical reactions (weathering).
- Water - The presence or absence of water decides the chemical reactions. Also, when water is added or removed it imposes mechanical stress on the rocks and causes it to split.
- Organisms - It includes the action of roots of plants, decomposing vegetations and burrowing animals.
Types of weathering -
- Physical weathering/Mechanical weathering
- Chemical weathering
- Biological weathering
Physical Weathering
- Disintegration of rocks takes place without any change in chemical constituents of rocks.
- Factors such temperature, moisture, frost action and wind cause physical break up of rocks.
- It is more rapid in desert (Arid) climate.
- Rocks are affected to great depth.
- Its agents are temperature and moisture.
Chemical Weathering
- Decomposition of rocks takes place with changes in the chemical constituents of rocks.
- Temperature, moisture, frost action, etc cause minerals in rocks to either dissolve in water or change their composition.
- It occurs in moist and cold climate.
- It mostly takes place near to the surface of the Earth.
- Its agents are water, Oxygen, Carbon and Various organic acids.
Biological Weathering - It involves breaking of particles by burrowing animals, pressure exerted by plant roots, decomposing organic matter which releases different chemicals and also the reactions with various micro-organisms which may bring changes in rocks.
Types of Physical Weathering -
1. Crystal Growth
- Frost Shattering (Arid) & Freeze Thaw (Polar)
- Haloclasty/Salt Weathering
2. Pressure/Thermal expansion
- Pressure release
- Exfoliation
- Rock disintegration
- Granule disintegration
Crystal Growth (Water) - When water freezes, it expands and finds its way in cracks or pores and it wedges apart rock fissures and joints.
It is Frost Shattering in case of Arid region and Freeze Thaw in Glacial region.
Salt Weathering/Haloclasty - Salt Weathering is the growth of salt crystals by crystallization as moisture evaporates, thus exerting pressure in pore spaces and cracks. It is also known as Haloclasty.
Pressure/Thermal Expansion - It involves the break down of rocks due to expansion of rocks caused by increase in temperature or decrease in pressure.
It is of 4 types -
- Pressure release
- Exfoliation
- Block disintegration
- Granular disintegration
Pressure release - The confining pressure from the weight of overlying rocks is released when the overlying cover is removed by erosion. This causes rocks to expand leading to the development of fractures.
Exfoliation - Rapid expansion and contraction of the surface rocks weakens the shell creating fissures causing the rock shell to peel off.
Block disintegration - When the rocks disintegrates as different blocks.
Granular disintegration - When the rocks are degraded as small granules.
Types of Chemical Weathering -
- Hydrolysis
- Hydration
- Oxidation/Reduction
- Carbonation
Hydrolysis - It is the chemical union of water and minerals resulting in solution. It involves specific chemical changes in which new material is produced.
Hydration - It occurs when minerals incorporate water into their molecular structure. It causes swelling.
Oxidation/Reduction - It is the addition or removal of oxygen and it causes discoluration. It is the first visible sign of chemical weathering.
Carbonation - Rain water absorbs Carbon di-oxide as it falls through air and gets converted into carbonic acid. Lime Stone and Dolomites are altered by the dissolving action of Carbonic acid.
Erosion
Erosion - It refers to the wearing away of land surface by the mechanical action of debris derived from weathering as they are transported to different locations by agents like wind, water, glacier, etc.
Weathering vs Erosion -
- Weathering - disintegration at its own place (no transportation)
- Erosion - disintegrated particles are carried away by different agents
Types of Erosion -
- Abrasion - rubbing of surface (Corrasion - in case of water)
- Attrition - rubbing against each other
- Corrosion - solvent action
- Cavitation - bubble impact of rivers at banks
- Deflation - lifting of smaller rocks by wind
- Plucking - glacial impact
- Hydraulic action - lifting and breaking of rock by running water
Abrasion - Wearing away of surface by mechanical processes like rubbing, scratching, polishing, etc.
Corrasion - If abrasion happens inside the water.
Attrition - It involves reduction in the size of fragments by friction and impact during transportation. It breaks down the loads into finer sediments.
Corrosion - It involves wearing away of particles by the solvent and chemical action of water.
Cavitation - The collapse of bubbles of water in river leads to explosion, sending a shock wave which tends to disintegrate the adjacent rocks.
Deflation - Lifting and removal of dust and sand by wind. It involves Arial erosion, removal of unconsolidated materials, etc
Hydraulic Action - The breaking away of rocks by fast moving water is called hydraulic action.
Plucking - As the glacier moves, they drag the rocks and disintegrate it into smaller pieces.
Mass Movement
Mass Movement - Mass in movement under the influence of gravity is called Mass Movement.
The weathered materials can move along the downhill slope under the influence of gravity with or without the assistance of running water.
Types of Mass Movement -
1. Slow Mass Movement
- Soil Creep
- Solifluction
2. Rapid Mass Movement
- Landslide
- Earth flow (bigger version of Soil creep)
- Mud flow (bigger version of Solifluction)
- Rock slide
- Rock fall
Soil Creep - It is the slope down hill movement of soil and weathered material. It is very slow and is difficult to notice but is a continuous movement.
Solifluction - It involves the slow movement of soil mixed with water as a viscous fluid. It is more active in glacial region.
Earth flow - It forms on terraces and will sight where they are capable of flowage when saturated with water that occurs beneath the Earth's layer.
Mudflow - It involves rapid movement of masses of uncompacted soil that are suddenly saturated with water.
Mudflows occur mostly
in mountainous places where a long dry season is
followed by heavy rains.
Rock slide - It is the rapid movement of rock material along the mountain slope.
Rock fall - It involves falling of rocks in a vertical direction along the cliffs and mountain regions.
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Note - This is my Vision IAS Notes (Vision IAS Class Notes) and Ashutosh Pandey Sir's Public Administration Class notes. I've also added some of the information on my own.
Hope! It will help you to achieve your dream of getting selected in Civil Services Examination 👍
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