Weathering and its types – Geography Notes PDF in English & Hindi for UPSC and Other Competitive Exams

Weathering and its types: Weathering is the natural process by which rocks and minerals on the Earth’s surface break down or disintegrate due to various mechanical, chemical, and biological factors. Weathering plays a significant role in the shaping and transformation of Earth’s landscapes. There are two main types of weathering: mechanical (physical) weathering and chemical weathering. Additionally, biological weathering is a subset of both mechanical and chemical weathering and is caused by the activities of living organisms.

  • Weathering is the action of components of weather and climate materials over Earth.
  • There are several processes within weathering which act either independently or together to affect the materials of the earth in order to cut them to fragmental state.
  • This process causes the disintegration of rocks near the surface of the Earth.
  • It loosens and breaks down the surface minerals of rocks so they can be carried away by agents of erosion such as wind, water, and ice.
  • As very little or no motion of materials takes place in weathering, it is an in-situ or on-site process.
  • Flora and fauna life, water and atmosphere are the main reasons for weathering.
  • Weathering processes are determined by many climatic, topographic, vegetative factors and complex geological factors.
  • Climate has a significant role in weathering.
  • The weathering processes not only differ from climate to climate but also with the depth of the weathering mantle.
  • The degree of weathering that happens depends upon the resistance to weathering of the minerals in the rock and the degree of the biological, physical, and chemical stresses.
  • The minerals in rocks that are formed under high pressure and temperature inclined to be less resistant to weathering, whereas minerals formed at low pressure and temperature are more resistant to weathering.

Types of Weathering

  1. Mechanical (Physical) Weathering:
    • Mechanical weathering involves the physical breakdown of rocks into smaller fragments without altering their chemical composition.
    • Common mechanisms of mechanical weathering include: a. Frost Action (Frost Wedging): Water seeps into cracks in rocks, and when it freezes, it expands, exerting pressure on the surrounding rock. Repeated freezing and thawing can widen the cracks and break the rock apart. b. Exfoliation (Onion-Skin Weathering): This occurs in rocks, particularly igneous rocks, where the outer layers peel away due to pressure release as they are exposed to the Earth’s surface. c. Abrasion: Rocks are physically worn down by the abrasive action of wind, water, ice, or other particles carried by these agents. d. Biological Activity: The activities of plants and animals, such as plant roots growing into cracks and burrowing animals, can physically break down rocks. e. Thermal Stress: Daily temperature fluctuations can lead to the expansion and contraction of rocks, causing them to crack and break over time.
  2. Chemical Weathering:
    • Chemical weathering involves the alteration of the mineral composition of rocks through chemical reactions.
    • Common mechanisms of chemical weathering include: a. Hydration: The addition of water to minerals can cause them to expand and break apart. b. Hydrolysis: Water reacts with minerals, causing them to break down into new compounds. For example, feldspar can weather into clay minerals through hydrolysis. c. Oxidation: Oxygen in the atmosphere can react with minerals, causing them to rust or change color. Iron-bearing minerals are particularly susceptible to oxidation. d. Carbonation: Carbon dioxide from the atmosphere can dissolve in water, forming carbonic acid. This weak acid can react with minerals like limestone (calcium carbonate) to dissolve and break them down.
  3. Biological Weathering:

    • Biological weathering is the result of living organisms contributing to the breakdown of rocks and minerals.
    • Plant roots can physically break rocks as they grow into crevices.
    • Some microorganisms and plants can release acids that chemically weather rocks.
    • Burrowing animals can loosen and disintegrate rocks as they dig through them.

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By Team Learning Mantras