Geomorphology and Surface Processes
What this domain tests
Geomorphology and Surface Processes tests weathering, erosion, transport and deposition, the landforms they produce, and how climate and tectonics control landscapes. Cameroon examples - lateritic plateaus, the Adamawa uplift, the Sanaga and Benue drainage, the Wouri delta and the volcanic line - are common.
Core rules and concepts
- Weathering is in situ breakdown: physical (freeze-thaw, salt crystallisation, unloading/exfoliation), chemical (hydrolysis of feldspar to clay, oxidation of iron, carbonation and solution of limestone) and biological.
- Laterite and bauxite form by intense chemical weathering in humid tropical climates: soluble bases and silica are removed, iron and aluminium oxides remain. A duricrust is a hardened surface layer; bauxite is an aluminium-rich residual deposit.
- Fluvial processes: drainage patterns reflect structure and lithology - dendritic on uniform rocks, trellis on folded strata, radial on domes and volcanoes, rectangular on jointed rocks. Rivers adjust their long profiles to base level; terraces record uplift or climate change.
- Slope processes: creep, solifluction, landslides, rockfall; angle of repose.
- Coastal processes: wave refraction, longshore drift, spit and barrier formation, deltas where sediment supply exceeds wave removal.
- African erosion surfaces: successive planation surfaces (Cretaceous, Eocene, Miocene-Pliocene, Quaternary) preserved on stable cratons and dissected after uplift.
Worked example
A plateau at 1,200 m has flat tops capped by iron duricrust, steep escarpments and deeply incised rivers with waterfalls at the escarpment. The flat tops are remnants of an old planation surface; the duricrust protected them from erosion. The incision and waterfalls show tectonic uplift rejuvenated the rivers. The landscape is therefore polycyclic: an ancient surface uplifted and partly destroyed, not a single young erosion surface.
Traps that cost marks
Confusing weathering with erosion; calling any red soil laterite (laterite is a residual weathering product, not a soil order); assuming flat tops are always structural; interpreting drainage patterns without checking joints and folds; forgetting that sea-level change and tectonics both produce terraces; ignoring climate as a control on chemical weathering.