Three agents of landscape change
Water, wind, and ice are the primary sculptors of Earth's landscapes. Rivers erode steep valleys and deposit sediment on floodplains. Glaciers carve U-shaped valleys and deposit moraines of unsorted rock. Wind abrades cliffs and fills deserts with sand. Each agent leaves a diagnostic landform: river canyons, glacial cirques, wind-carved arches, or dune fields.
Balance and dynamic equilibrium
In a stable landscape, erosion and deposition are balanced: a river erodes its upstream banks while depositing sediment on its bends and floodplain. Disruption of this balance (climate change, tectonic activity, human intervention) creates rapid erosion or unexpected deposition. Damming a river stops deposition downstream; cutting a forest accelerates erosion uphill.