07-01-2026 Mains Question Answer
What is Denudation? Describe the process involved.
Denudation is the process of wearing away and stripping the Earth’s surface through the combined actions of weathering, erosion, and mass wasting, which lowers the land’s elevation and relief. It involves breaking down rock and soil and then moving it via agents like water, wind, ice, and gravity. The term comes from the Latin “denudare,” meaning “to strip” or “uncover“.
Denudation encompasses several sequential processes:
| 1) Weathering | Weathering is the in-situ breakdown of rocks at or near the Earth’s surface without transportation. It can be of various types: 1. Physical/ Mechanical Weathering: a. Involves mechanical disintegration of rocks without chemical alteration. b. Caused by temperature variations, frost action, unloading, salt crystallisation and biological activity. c. Important mechanisms: i. Unloading and Expansion: Removal of overlying rock pressure causes expansion of underlying rocks, leading to cracking and exfoliation. ii. Exfoliation: Peeling off of curved rock layers, producing smooth, rounded surfaces and exfoliation domes. iii. Temperature Changes: Repeated heating and cooling cause expansion and contraction, leading to rock fracture. iv. Freeze–Thaw (Frost Wedging): Water freezes in cracks, expands and widens joints until rocks break apart; common in cold and mountainous regions. 2. Chemical Weathering: a. It involves chemical alteration and decomposition of minerals. b. Major processes: i. Solution: Soluble minerals dissolve in water or weak acids and are removed. ii. Carbonation: Carbonic acid dissolves carbonate minerals like limestone, leading to cave formation. iii. Hydration: Minerals absorb water, expand and weaken the rock structure. iv. Oxidation and Reduction: Reaction with oxygen alters minerals, especially iron, weakening rocks and changing colour. 3. Biological Weathering: a. Caused by plants, animals and microorganisms. b. Includes root penetration, burrowing animals, microbial activity and organic acids produced by lichens and bacteria. c. Acts both physically and chemically on rocks. |
| 2) Erosion | 1. Erosion involves the removal and movement of weathered material. 2. Agents include running water, wind, glaciers, sea waves and gravity. 3. Responsible for shaping valleys, cliffs, dunes and other landforms. |
| 3) Transportation | 1. Transported materials move through traction, suspension, saltation and solution, depending on the agent. 2. Different agents produce distinctive geomorphic features. |
| 4) Deposition | 1. Occurs when transporting agents lose energy. 2. Leads to formation of deltas, floodplains, alluvial fans, beaches and moraines. 3. Marks the final stage of the denudational cycle. |
Denudation is a comprehensive geomorphic process that gradually lowers landforms through the integrated action of weathering, erosion, transportation and deposition. It plays a crucial role in shaping Earth’s surface and maintaining long-term landscape balance.