Geomorphology and Surficial Processes
What to know
Landscapes reflect weathering (physical, chemical, biological), erosion, transport, and deposition acting on uplifted rock. Mass wasting is classified by material (rock, debris, earth) and movement (fall, slide, flow, creep); slope stability is limited by a threshold angle set by friction and pore pressure. Fluvial systems follow discharge Q = w·d·v, with channel form adjusting to sediment load and bank material; sinuosity = channel length ÷ valley length. Base-level change propagates incision or aggradation upstream.
Glacial systems produce U-shaped valleys, striations, till, moraines, drumlins, eskers, and outwash. Coasts respond to wave refraction, longshore drift, and sediment supply. Karst develops where soluble rock permits focused groundwater flow, producing sinkholes, sinking streams, and caves. Drainage patterns record structure: dendritic (uniform), trellis (folded), radial (domes), rectangular (jointed).
Two end-member views: Davis's cyclic peneplanation versus dynamic equilibrium, where form adjusts continuously to process and rock resistance.
Traps
Equating weathering with erosion (weathering produces regolith in place); calling a U-shaped valley fluvial; assuming a stream's velocity depends only on gradient (discharge and roughness matter); forgetting that sinuosity > 1.5 defines meandering; treating alluvial fans and deltas as the same feature.
Rule of thumb
Stream competence scales roughly with v²; capacity with Q and slope. Doubling width or depth doubles Q; doubling velocity quadruples the size of sediment that can be moved.
Worked example: a 20 m wide, 2 m deep channel with mean velocity 1.5 m/s carries Q = 20 × 2 × 1.5 = 60 m³/s.