Geomorphology and lithosphere
Geomorphology and lithosphere
WBCHSE tests whether you can move from a named process to a landform and back again, quoting the field evidence. Expect plate-margin diagrams, weathering classifications, the Davisian and Penckian cycles of erosion, and identification of fluvial, glacial, aeolian and coastal landforms.
Core rules
- Endogenetic processes = diastrophism (folding, faulting, epeirogeny) plus volcanicity; exogenetic = weathering, mass wasting, erosion, transportation, deposition.
- Weathering is in-situ disintegration and decomposition; erosion involves removal and transport by an agent. Do not use the two interchangeably.
- Divergent margin → mid-oceanic ridge and rift valley; ocean–ocean convergence → trench with island arc; continent–continent convergence → fold mountains; transform margin → transcurrent faults.
- Karst needs soluble rock (limestone/chalk), joints and bedding planes, and a humid climate.
Worked example
A limestone plateau shows swallow holes, dry valleys, dolines and a cave with stalactites. Name the process and landform group. Reasoning: jointing gives secondary permeability, so rainwater plus soil CO₂ forms weak carbonic acid; CaCO₃ + H₂CO₃ → Ca(HCO₃)₂, which is soluble and is carried away underground. Surface result = karst (doline, swallow hole, dry valley); underground result = cavern, with speleothems deposited when the bicarbonate solution degasses. The agent is chemical solution, not abrasion, so the answer must not mention attrition or hydraulic action.
Traps that cost marks
Calling a V-shaped valley glaciated; confusing a delta (depositional, distributary channels) with an estuary (drowned valley, tidal scour); giving "peneplain" for Penck's "endrumpf"; describing exfoliation as chemical when it is onion-skin mechanical peeling; naming a landform without stating the process that produced it.