Erosion is the natural process of loosening and removing weathered solid material from landscapes by water, wind, ice or gravity.
Physical erosion occurs through various processes that sculpt rocks into ventifacts or even move entire mountains, as well as through gravity’s gradual disintegration of rock, soil, and other materials. Tree growth may also help slow this type of physical erosion.
Water
Water is the main agent behind erosion – whether in rivers, streams or wetlands – as its movement transports soil and rocks away and deposits them elsewhere – known as physical or mechanical erosion as opposed to weathering which does not involve movement.
Water erosion tends to occur more in hilly or sloping areas where land is exposed, as well as when trees and plants have been removed, such as deforested areas or commercial farmland. Gully or rill formation often follows, leading to downstream effects like flooding, sedimentation and clogged waterways.
Wind can also play a significant role in erosion, particularly in dry or semi-arid regions with sparse vegetation. When winds blow, fine soil particles are carried away by the currents – this phenomenon is known as wind erosion – forming features like deserts or fertile delta soils of rivers.
Wind
Wind can cause erosion by blowing soil particles off of the ground, with larger particles such as clay or silt traveling longer distances while smaller sand-sized particles tend to remain localized – an effect often found in arid regions. Furthermore, wind has the power to alter rock shapes – it can wear away smooth spots on sandstone, creating canyons. Furthermore, it can move sand from place to place creating towering dunes.
Rivers can transport away sediment in the form of sand, pebbles and rock; this form of erosion known as aeolian helps shape rivers and canyons over time – such as helping create the Grand Canyon in southwestern United States.
Erosion occurs when people clear forests and plants. Without trees and plants to absorb rainfall, soil loses its ability to retain it; water therefore runs off more quickly over the land rather than seeping in slowly, causing flooding and sedimentation (a build-up of dirt in rivers). Clogged dirt may harm crops as well as pollute drinking water supplies.
Sediment
Sediments are fragments of rock broken apart through weathering and erosion processes that have been carried away by water, wind or glaciers and eventually deposited on riverbeds, floodplains, coasts or estuaries as sediment. Over time this material can become buried underground and eventually transform into sandstone or siltstone through the process of lithification.
Sludges and sediments are separated during transportation by factors such as flow strength, size, volume and density. Sands and gravels tend to separate more readily while coarser rocks remain mixed within the water body. Over time, random abrasion causes sharp corners of grains to round off gradually.
Human activities such as agriculture, urban development, construction and mining can significantly change sediment movement’s natural course within the geological cycle. By altering erosion rates and depositional patterns of rivers and lakes, this alters fish, birds, amphibians and aquatic organisms’ natural habitats. Sediment pollution also poses risks to humans – when mud clogs streams preventing sunlight reaching native water plants leading to low stream turbidity (cloudy water). Furthermore it carries nutrients such as phosphorus which causes algal blooms which leads to bad tasting drinking water sources – something natural doesn’t do.
Ice
Glaciers can erode the earth and form dramatic landforms. When glaciers move slowly down mountain valleys they scrape against rocks and soil before carrying it with them as they melt, leaving behind corries, aretes, pyramidal peaks, truncated spurs, steep-sided mountain valleys ribbon lakes and deposits called moraine deposits.
Glacial erosion occurs through various mechanisms depending on its location and climate conditions, including abrasion, plucking and freeze-thaw weathering.
Subglacial erosion refers to processes occurring at the base of glaciers and involves direct observation of their bed surfaces, unlike with other erosion processes. Due to their difficulty of observation, direct studies on landforms eroded by glaciers have yet to take place1. One common process used by glaciers for subglacial erosion is “striation”, scoring or “striation” of bedrock through embedding rocks particles on its surface and into bedrock particles embedded into it.