The earth is sculpted not in a day, but grain by grain, flood by flood. — Anonymous
5.1 Endogenic and Exogenic Processes
Geomorphic processes shape the earth's surface:
- Endogenic (internal): driven by energy from within the earth — diastrophism, volcanism, earthquakes
- Exogenic (external): driven by solar energy and gravity — weathering, erosion, transportation, deposition
Diastrophism includes orogenic processes (mountain building) and epeirogenic processes (continental uplift/subsidence).
5.2 Weathering
Weathering breaks down rocks in situ without transport:
| Type | Mechanism | Example |
|---|---|---|
| Physical | Freeze-thaw, exfoliation, salt crystallisation | Spalling of granite in deserts |
| Chemical | Oxidation, carbonation, hydration | Karst landscapes in limestone |
| Biological | Plant roots, burrowing animals | Tree roots splitting rock |
Weathering prepares material for erosion. In India, chemical weathering dominates in humid regions; physical weathering in arid and high-altitude areas.
5.3 Erosion and Transportation
Erosion removes weathered material. Agents:
- Running water — rivers carve valleys; dominant in India (Ganga, Brahmaputra systems)
- Wind — deflation and abrasion in deserts (Thar Desert)
- Glaciers — plucking and abrasion (Himalayas, Ladakh)
- Waves — coastal erosion (Konkan, Odisha coast)
- Groundwater — solution and piping (karst in Meghalaya)
Gradation tends to reduce relief; aggradation builds it up through deposition.
5.4 Mass Movements
Mass wasting moves material downslope under gravity: landslides, slumping, debris flows, soil creep.
Heavy monsoon rains trigger landslides in the Western Ghats and Himalayas. Deforestation and road construction increase vulnerability.
Chapter Summary
- Endogenic processes build relief; exogenic processes wear it down
- Weathering: physical, chemical, and biological breakdown in situ
- Erosion agents: water, wind, ice, waves, groundwater
- Mass movements common in India's mountainous and monsoon regions
- Geomorphic processes operate together over geological time
Exercises (NCERT)
- Exercise 1 — endogenic vs exogenic processes
- Exercise 2 — types of weathering with Indian examples
- Exercise 3 — agents of erosion and mass movement