Landforms and Geomorphic Agents
~11 min read
- Geomorphic agents: Running water (fluvial), glaciers, wind (aeolian), sea waves (marine), groundwater (karst), gravity (mass movement).
- Fluvial landforms: V-valleys, gorges, meanders, oxbow lakes, deltas, floodplains, alluvial fans.
- Glacial landforms: U-valleys, cirques, horns, moraines, drumlins, fjords.
Landforms are surface features shaped by geomorphic agents. Each agent produces signature landforms — knowing the agent tells you the landform's origin, and vice versa. NDA tests both directions.
Fluvial (Running Water) Landforms
| Stage | Landform | Example |
|---|---|---|
| Upper / youth | V-shaped valleys, waterfalls, rapids, gorges | Grand Canyon, Bhedaghat (Narmada) |
| Middle / maturity | Meanders, oxbow lakes, floodplains, alluvial fans | Middle Ganga; Mississippi |
| Lower / old age | Deltas, levees, distributaries | Sundarbans (Ganga delta), Nile delta |
Largest delta: Ganga–Brahmaputra (Sundarbans, ~10,000 km²).
Glacial Landforms
- Erosional: Cirques (armchair hollows), horns (sharp peaks — Matterhorn), aretes (ridges), U-shaped valleys, hanging valleys.
- Depositional: Moraines (rock debris dropped by ice), drumlins (oval hills), eskers (ridges), outwash plains.
- Coastal glacial: Fjords — drowned U-valleys (Norway, New Zealand, Chile).
Wind (Aeolian) Landforms
Wind action is most prominent in arid regions where vegetation is sparse.
- Erosional: Yardangs (parallel ridges), mushroom rocks (zeugen), ventifacts, deflation hollows.
- Depositional: Sand dunes (barchans, seif, transverse), loess (wind-deposited fine silt). Thar Desert has barchan dunes; loess deposits dominate the Chinese Yellow River plains.
Marine and Karst Landforms
Marine (sea wave) erosion: Sea cliffs, sea caves, arches, stacks, wave-cut platforms, headlands. The Twelve Apostles (Australia) and stacks of the Andaman coast are famous examples.
Marine deposition: Beaches, spits, bars, tombolos, lagoons. Chilika Lake (Odisha) is a coastal lagoon.
Karst (limestone) landforms: Caves (Borra in Andhra Pradesh, Mawsmai in Meghalaya), sinkholes, stalactites (hanging), stalagmites (rising from floor), dolines.
NDA PYQ Examples
Q: Oxbow lakes are formed by which agent?
(a) Wind (b) Glaciers (c) Rivers (d) Sea waves
Answer: (c) Rivers — abandoned meanders cut off from the main channel.
Q: Which is the largest delta in the world?
(a) Nile (b) Amazon (c) Ganga-Brahmaputra (Sundarbans) (d) Mississippi
Answer: (c) Ganga-Brahmaputra — Sundarbans, ~10,000 km².
Q: Barchan dunes are formed by:
(a) River deposition (b) Glacier erosion (c) Wind (d) Sea waves
Answer: (c) Wind — crescent-shaped dunes in deserts.
Drill Landforms and Geomorphic Agents for NDA
NDA-pattern items on Landforms and Geomorphic Agents with answer keys and explanations.
Start Free Mock TestFrequently Asked Questions
Why do rivers form meanders?
In the middle stage of a river, slight curves are amplified by faster flow on the outside (eroding) and slower flow on the inside (depositing). Over time, this widens curves into pronounced meanders that may eventually be cut off as oxbow lakes.
What is a fjord?
A long, narrow, deep coastal inlet formed when sea water floods a U-shaped glacial valley after the ice retreats. Common in Norway, Chile, New Zealand.
Where does loess come from?
Wind-deposited fine silt, often from glacial outwash or deserts. The largest loess deposits are in China (Yellow River plateau), formed from Gobi Desert dust over millennia.
How are stalactites and stalagmites different?
Both form in caves from mineral-rich water drops. Stalactites hang from the ceiling (think 'c' for ceiling). Stalagmites rise from the floor (think 'g' for ground). They sometimes meet to form columns.
Which river has the largest waterfall in India?
Jog Falls (Sharavathi River, Karnataka) is among the highest at 253 m. Kunchikal Falls (Karnataka) on the Varahi River is the tallest at 455 m by one count.