Erosion is the process by which soil, sediment and rock are detached and transported from one location to another by moving agents such as water, wind, ice and gravity. It is a fundamental component of landscape evolution and operates on timescales ranging from individual storms to millions of years. Erosion differs from weathering because weathering alters or breaks down material in place, whereas erosion involves removal and transport.
Erosion also differs from deposition, which occurs when transported material is laid down in a new location. In natural systems these processes operate together, producing a continuous cycle in which material is weathered, eroded, transported and deposited, then potentially lithified and incorporated into the geological record.
Water is one of the most important agents of Erosion. Rainfall can detach soil particles through raindrop impact, while overland flow can transport sediment across slopes. Concentrated runoff produces rills and gullies and can eventually develop into channels capable of carrying substantial sediment loads. Rivers erode their beds and banks through hydraulic action, abrasion and other processes, while transported sediment can itself act as an abrasive tool. River Erosion can deepen valleys, migrate channels and reshape floodplains. The amount and type of sediment transported depend on discharge, flow velocity, channel geometry, sediment size, bed roughness and sediment availability.
Wind Erosion is particularly important in dry, sparsely vegetated environments where loose sediment is exposed to strong airflow. Wind can move fine particles over considerable distances through suspension, while larger grains may travel by saltation or creep along the ground. Abrasion occurs when wind transported particles strike exposed rock surfaces, gradually modifying their shape and texture. Vegetation strongly influences wind erosion because plant cover reduces wind velocity near the ground and binds soil with roots. Human removal of vegetation can therefore increase vulnerability to wind erosion. Dust generated by erosion can influence air quality, nutrient transport and atmospheric chemistry when it is transported far from its source.
Ice contributes to Erosion primarily through glaciers and ice sheets. Moving glacial ice can incorporate rock fragments and drag them across underlying surfaces, producing abrasion and striations. Glaciers can also pluck blocks from fractured bedrock and transport enormous quantities of sediment. Over long periods, glacial erosion can produce distinctive landscapes including broad valleys, cirques, overdeepened basins and other landforms. Glacial erosion depends on ice thickness, velocity, thermal conditions, bedrock properties, sediment availability and subglacial water. Because glaciers can move over very large areas, their erosional effects provide important evidence for reconstructing past climates and ice sheet extent.
Erosion is influenced strongly by vegetation, soil structure, slope, climate and human land use. Plant roots can stabilise soil and increase resistance to detachment, while leaf litter and surface organic material can reduce the direct impact of rainfall. Deforestation, overgrazing, intensive cultivation and poorly planned construction can expose soil and accelerate erosion. Agricultural soil erosion can remove nutrient rich topsoil and reduce long term productivity. Conservation approaches can include maintaining vegetation cover, reducing unnecessary soil disturbance, managing drainage and designing slopes to reduce concentrated runoff. The appropriate approach depends on the local climate, soil properties, topography and land use.
Coastal Erosion is another major expression of the process and occurs where waves, currents, tides and storms remove material from shorelines. Wave impact can exploit cracks and weaknesses in cliffs, while abrasion by transported sediment can gradually wear exposed surfaces. Longshore sediment transport can redistribute material along coasts, and changes in sediment supply can cause some beaches or shorelines to retreat. Sea level changes, storm frequency, coastal geology, sediment availability and human structures all influence coastal erosion. Coastal engineering can reduce erosion locally but may also alter sediment transport and redistribute erosion elsewhere. Understanding coastal systems therefore requires considering the entire sediment transport network rather than treating individual beaches as isolated units.
Erosion plays a major role in the geological cycle because it transfers material from elevated regions toward lower areas and ultimately into sedimentary basins. Sediments produced through erosion can accumulate in rivers, lakes, deltas, continental shelves and deep marine environments. Burial and lithification can transform these sediments into sedimentary rocks, which may later be uplifted and exposed to weathering and erosion again. Erosion also influences global chemical cycles because the removal of minerals from continents can transfer elements into rivers and oceans. The rates of erosion can therefore affect landscape development, sediment budgets, nutrient transport and long term carbon cycling.
Erosion is often treated only as a damaging process, but it is also essential to natural geomorphological functioning. It creates valleys, transports nutrients and sediment, supplies material to beaches and floodplains, and contributes to the formation of sedimentary rocks. Problems arise when erosion rates become much greater than natural soil formation or sediment replenishment, particularly where human activities expose fragile surfaces. Measuring erosion can involve sediment traps, river sediment monitoring, erosion pins, aerial imagery, topographic surveys, satellite observations and modelling. A complete understanding therefore requires distinguishing natural background erosion from accelerated erosion and considering both the beneficial geological functions and the environmental or economic consequences of excessive rates.
