Geomorphology and Soils
What this domain tests
Geomorphology and soils tests landform-making processes - weathering, mass movement, erosion and deposition by running water, ice, wind, waves and groundwater - plus the major soil groups of India and Andhra Pradesh, their profiles, fertility and conservation. Expect identification of landforms from process descriptions and soil from parent material and properties.
Core rules
- Weathering is in situ breakdown: physical (frost, exfoliation), chemical (solution, oxidation, hydrolysis) and biological. Erosion transports the debris.
- The Davisian cycle moves from youth (V-shaped valleys, waterfalls) through maturity (meanders, floodplains) to old age (peneplain); rejuvenation resets it.
- Fluvial landforms: alluvial fan, delta, oxbow lake, levee. Glacial: cirque, arête, U-shaped valley, moraine. Aeolian: barchan, yardang, loess. Coastal: cliff, spit, bar. Karst: sinkhole, stalactite.
- Indian soil groups: alluvial, black (regur), red, laterite, desert, mountain, saline–alkaline, peaty. Black soil is basaltic, clay-rich, self-ploughing, moisture-retentive and cotton-friendly but low in humus. Red soil is from crystalline rock, iron-rich, often acidic and low in nitrogen. Laterite forms under heavy leaching.
- AP: black soils in Rayalaseema, red soils in uplands, alluvium in the Godavari–Krishna delta, saline patches near the coast.
Worked example
A sample is dark, clayey, cracks in summer, holds moisture, has pH 7.5–8.5, derives from basalt and supports cotton. Reason: dark colour, high clay, cracking and basalt parent material point to black regur soil. Laterite would be red, leached and acidic; alluvium would be stratified and lighter.
Traps
Treating red soil as always fertile; confusing laterite with red soil; forgetting that alluvium can be nitrogen-poor; naming a landform without its agent.