Landforms in the tropics

H2 Geography - syllabus 9173, 2027

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Explain how rocks, slopes and rivers change, then connect those processes to tropical karst, meanders, braided channels and deltas.

• Chemical weathering processes

  Chemical weathering alters or dissolves minerals in place. Water chemistry and mineral composition determine the reaction.

• Physical weathering processes

  Physical weathering breaks rock without changing its mineral composition. Each process needs particular conditions.

• Controls on tropical weathering

  Climate supplies conditions for weathering; rock, water pathways, organisms, time and human activity control how those conditions act.

• Falls, flows, creep and slides

  Mass movement occurs when downslope driving forces exceed the strength resisting movement. Rain can add weight and weaken resistance.

• Splash erosion, rainwash and rillwash

  Raindrops detach particles; overland flow carries them away. Concentrated runoff can cut small channels called rills.

• River erosion and sediment transport

  Rivers erode and transport material in several ways. Dissolved ions travel in solution even when the water looks clear.

• River energy and deposition

  Deposition occurs when transport can no longer sustain part of the load. Grain size, cohesion and turbulence make thresholds differ.

• Cockpit karst and tower karst

  Carbonate dissolution, drainage and relief shape karst. Rock structure and landscape history help determine whether cones, depressions or towers remain.

• Cave openings and speleothems

  Dissolution enlarges cave openings. Changed water chemistry can then precipitate calcite as speleothems inside air-filled passages.

• Karst ecosystem services and human pressures

  Karst supports water supplies, habitats and cultural value. Connected underground drainage also allows damage to spread beyond the visible site.

• Meanders, river cliffs and point bars

  A meander migrates through outer-bank erosion and inner-bank deposition, linked by the three-dimensional movement of water and sediment.

• Braided channels and mid-channel bars

  Braiding develops where abundant sediment, variable flow and erodible banks support mobile bars and repeated channel division.

• Delta formation and coastal processes

  A delta grows where river sediment accumulates at the mouth faster than it is removed, while deposition keeps pace with available space.

• Delta services and human pressures

  Deltas support dense livelihoods through sediment, freshwater and wetlands. Activities upstream and within the delta can weaken these services.