Erosion and deposition are natural processes that alter Earth’s landscape through erosion and deposition, creating landforms such as sandy beaches, deltas, and spits.
Erosion begins with weathering, which breaks down rock. Erosion then transports away broken down rock and soil from their original locations.
As energy wanes in an eroding agent, its load of material eroded from it declines accordingly and deposits vary according to size and weight.
Agents of Erosion
Erosion refers to any force that moves rock and soil particles from their original positions; it’s a natural process and occurs all around us; gravity, wind, water and ice are primary agents of erosion; however flowing water has the most severe effect of all.
Water erodes sediments through scouring, shearing, removal and dissolution (see Chapter 14 Weathering). The faster water flows in a stream the greater its erosional capacity.
Wind can also erode soil material, particularly in dry climates. Wind currents carry dust particles over long distances – as happened during North America’s “Dust Bowl” of 1930s.
Vegetation reduces erosion by binding together soil and rock particles and anchoring them to the ground, while engineers often employ structures to combat wind and water erosion; one such structure is called gabions, a large wireframe which keeps boulders at bay near cliffs that threaten to collapse onto homes and cars.
Attrition
Attrition, or rock erosion by repeated impacts between rocks, is most visible on beaches where pebbles and sand grains collide repeatedly and wear down each other’s sharp edges, over time creating rounder sand grains. Attrition also plays an essential role in shaping riverbeds and smoothing coastlines.
Hydraulic action occurs when water flows over rock fragments or sediment in order to dislodge and transport them away from riverbeds or coastlines, dislodging and transporting away these materials in its path.
Abrasion is an erosional process that forms riverbeds and coastlines over time, shaping riverbeds with particles of rock and sediment rubbing against each other in response to wind, water, or ice. The strength of abrasion depends on factors such as load items’ size, shape, hardness and speed and duration of movement.
Solution is a chemical weathering process which dissolves minerals from rocks over time, such as limestone. Mildly acidic rainwater dissolves it gradually over time.
Transport
Erosion involves transporting sediment eroded from its original location to another. Depending on its surroundings, this may result in deposition or it could remain suspended and be carried downstream until they settle and form new soil formations.
Transport typically occurs via fluid systems like flowing water and wind. Sand tends to be carried and deposited more easily by running water than silt or clay because its larger particles are less abrasive than smaller ones.
Erosion and sediment transport prediction models come in various forms. These can be divided into categories depending on what kind of erosion they can model, as well as their ability to estimate net erosion within a catchment. Researcher or professionals embarking on sediment modelling projects may benefit from researching all available sediment modeling models; doing this can save them time in selecting an effective one that fits their case study.
Deposition
While erosion erodes away rocks and soil, deposition deposits them back where they belong. Deposition can occur as a result of wind or water action or through other natural processes as well.
Sand and rock deposits occur when waves break on coastal regions. Refraction causes waves to either focus their energy into crashes against cliffs or disperse it into small pieces which then break apart, depositing their sediment as sand into bays as part of this process.
Rivers transport rocks and dirt from places further upslope and deposit it downstream, creating sandy beaches, deltas, estuaries and spits as a result of erosion and weathering – these landforms result from both processes working together to alter existing landscapes while simultaneously creating new ones. Erosion rates depend on climate, topography, soil characteristics and vegetation cover as well as speed of the moving water as it affects how easily sediment can dislodge from its bonds.