- 2076 Chaitra · 1.5+1 marks
Soil and rock types of Himalayan zones
Short answer
Higher Himalaya: gneiss, schist, marble, quartzite, granite; thin residual soil, moraine. Midland: phyllite, slate, quartzite, limestone, dolomite; residual, colluvial soil, lacustrine clay in basins. Dun valleys: Siwalik sandstone, mudstone; alluvial gravel, sand, silt, clay. Eluvial soil is residual from weathering in place; lacustrine soil is fine, layered lake deposit, soft and compressible.
What are the soil types and rock types found in the Higher Himalaya zone, Midland zone and Dun Valleys? Differentiate eluvial soil and lacustrine soil.
| Zone | Rock types | Soil types |
|---|---|---|
| Higher Himalaya | Gneiss, schist, migmatite, marble, quartzite, granite | Thin residual soil, moraine and glacial deposits, talus and colluvium |
| Midland (Lesser Himalaya) | Phyllite, slate, schist, quartzite, limestone, dolomite, granite | Residual (eluvial) soil, colluvial soil, river terraces; lacustrine clay in basins (Kathmandu, Pokhara) |
| Dun valleys | Siwalik sandstone and mudstone on the borders | Alluvial and fluvial gravel, sand, silt and clay; colluvial fans |
Eluvial soil vs lacustrine soil
| Point | Eluvial (residual) soil | Lacustrine soil |
|---|---|---|
| Origin | Formed in place by weathering of the parent rock | Deposited in lakes by water and settled out |
| Transport | None | Carried by rivers and deposited in still water |
| Texture | Variable, grades into rock below | Fine, well sorted, layered silt and clay |
| Example | Soil on hill slopes of the Mahabharat | Kathmandu valley black clay and peat |
| Engineering | Moderate strength, may be deep | Soft, compressible, low bearing capacity, high water content |
✓ Answer checked by Claude Opus 5.5 (high effort)
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