Every valley has its river, and every river its story. — Anonymous
6.1 Geomorphic Cycle
W. M. Davis proposed the geographical cycle (cycle of erosion): landforms pass through stages of youth, maturity, and old age as rivers erode uplifted blocks. While simplified, it remains a useful framework.
Peneplain — a nearly flat surface formed by prolonged erosion.
6.2 Landforms by Running Water
Rivers create:
- V-shaped valleys and gorges (youthful stage) — e.g. Indus Gorge
- Meanders and oxbow lakes (mature stage) — e.g. Ganga plains
- Floodplains and deltas (old age) — e.g. Sundarbans delta
Waterfalls form where hard rock overlies soft rock or at fault scarps. Alluvial fans form where mountain streams enter plains.
6.3 Landforms by Wind and Glaciers
Aeolian landforms (wind):
- Erosional: deflation hollows, mushroom rocks, yardangs
- Depositional: sand dunes (barchans, seifs), loess plains
Glacial landforms:
- Erosional: cirques, U-shaped valleys, horns, arêtes
- Depositional: moraines, eskers, drumlins, outwash plains
Ladakh and Himachal Pradesh show glacial features; the Thar Desert shows extensive dune fields.
6.4 Coastal and Karst Landforms
Coastal: cliffs, sea caves, stacks, beaches, spits, bars, lagoons (Chilika Lake).
Karst (limestone regions): sinkholes, caves, stalactites, stalagmites — prominent in Meghalaya.
Groundwater forms dripstones in caves and alluvial terraces along rivers.
Chapter Summary
- Davis's cycle of erosion: youth, maturity, old age
- Fluvial landforms: valleys, meanders, deltas, floodplains
- Aeolian and glacial landforms in arid and high-altitude India
- Coastal and karst landforms shaped by waves and groundwater
- Landforms reflect the interaction of structure, process, and time
Exercises (NCERT)
- Exercise 1 — stages of the geomorphic cycle
- Exercise 2 — fluvial landforms with Indian examples
- Exercise 3 — wind, glacial, coastal, and karst landforms