Erosion is the natural process by which weathered rock and soil sediments are transported from one place to the next by natural forces such as weathering. When these forces have exhausted their energy supply, deposition occurs – this material falls back onto its previous site of origin.
Physical erosion wears away rocks, creating sand dunes and carving cliff faces into beautiful rock sculptures – like Arches National Park in Utah with its famous arches.
Wind
Wind can contribute to erosion by moving sand and dirt between locations. It may also loosen rock fragments from their sockets and carry them away; this process is known as aeolian erosion.
Wind erosion occurs most rapidly on unprotected rocky or sandy ground with no vegetation to protect it, and can occur very rapidly when combined with dust storms that sweep across desert landscapes. A dust storm carrying soil particles across such landscapes may remove and transport soil particles over great distances, potentially destabilizing them further along its journey.
Water and other erosion agents like ice, winds, waves, and gravity determine how much material is removed and deposited, with particle size having an effect on their transport; larger particles move more quickly across terrain while exerting greater energy to erode rocks or soil in their path.
Flowing water collects and transports larger rocks first before depositing smaller pebbles, sand and silt particles as it travels downstream. This deposition creates river deltas, flood plains and natural levees. Canyons and gorges may form from this process, while mountain streams erode V-shaped valleys to form waterfalls – as well as deposit mineral deposits like stalagmites and stalagmites in caves.
Water
Water erosion occurs when rain or melting snow runs across the ground, picking up particles of rock and soil before transporting them away in its path. Some particles travel further before being dumped back where they belong while others drop quickly near their source of water; clay- and silt-sized particles tend to travel further distances than their sand-sized counterparts.
Streams and rivers are major causes of erosion. Their currents erode the sides of their channels, as well as any land along their banks, potentially eroding it further still. Furthermore, streams may erode caves forming stalagmites and stalactites within.
Land and rock characteristics determine how quickly erosion takes place in an area. Mountain streams erode narrow V-shaped valleys more quickly than rivers flowing over gentle slopes do; slowly-flowing rivers create broad floodplains and may form meanders in their channels; those emptying into bodies of still water may deposit sediment, creating alluvial fans and deltas, making the floodplains fertile places to be.
Soil
Soil is the top layer of Earth’s crust, composed of organic matter, minerals, and organisms. Its erosion rate depends on factors such as texture, structure, amount of organic material present and permeability.
Silt and sand soils are among the most vulnerable to erosion, followed by clay-textured loam-textured soils and loamy soils with slow infiltration rates, high amounts of organic matter content and robust structures.
Erosion caused by water can occur unnoticed until much of the topsoil has been lost, severely hampering seed emergence, crop yield and growth and potentially damaging roads and buildings.
Sediment may be deposited locally (deposition) or far away, like in a river bed. When deposition occurs, amounts can range from small amounts forming mounds or ridges on slopes to filling valleys completely; its shape also influences erosion with gullies often appearing where vegetation is absent on steep slopes.
Human Activity
Human activity has a direct effect on erosion. Farming and logging activities increase soil erosion rates while altering sediment production, transport and storage7; alluvial deposits increase significantly as does landslide susceptibility8,9.
Erosion may take place slowly, such as the gradual wearing away of rocks by seawater waves; pebbles become pebbles before ultimately becoming sand on beaches. Erosion may also happen quickly in cases such as mudslides which form when water or gravity quickly wear away rock and soil layers.
Engineers attempt to reduce erosion by planting trees and using structures such as gabions – huge wireframes designed to hold boulders in place – as well as dams, which prevent streams and rivers from eroding their banks. Erosion is an essential natural process that creates stunning landscapes but it can also have negative consequences for people and the environment, particularly if it transports harmful chemicals or pollutants between areas.