Deposition, the process of adding material gradually to a landform over time, is one of the primary ways that creates and modifies landscape features – it can turn a meander into an oxbow lake for instance!
Gravity, wind, ice and water all help transport and deposit sediment. Once energy has been expended in transporting it to its final destination, however, sediment stops moving forwards and starts building up instead.
Sediment
Sediment is loose material such as rock fragments or soil that has been deposited by weather or human activity, often at beaches, wind blown sediments, stream deltas, river deltas or within stream deltas. Sediment can clog and damage underground pipes over time requiring costly repairs for sanitary sewers.
The rate at which sediment deposits depends on both geology and geomorphology as well as environmental conditions in an area, and factors like erosion. Erosion material transported by water, wind or ice transport networks is another significant contributor. Finally, different organic and inorganic materials contribute to creating sediment1.
Erosion
After weathering has dismantled rocks into smaller pieces, they can be picked up and moved from one location to the next by erosion and deposition processes respectively. Erosion refers to collecting rock materials before moving them, while deposition refers to depositing them at their new locations.
Erosion is an ongoing geological process that continuously transforms Earth’s landscape over time. Its causes include gravity, water, wind, ice and waves. Tectonic activity may also have an effect on this form of degradation by shifting plates’ positions in response to earthquakes.
Water is the primary agent of erosion. It carries and deposits rocks and soil particles over time, wearing away at the earth and creating canyons and other features as it goes. The size and shape of deposits left behind depend on how much energy the flowing water possesses – larger rocks will settle first followed by pebbles, sand, silt deposits.
Plants can contribute to erosion by planting roots into cracks in rocks. As their roots spread outward, widening these spaces over time and eventually breaking apart rocks into small fragments.
Weathering
Weathering causes rocks and soil surfaces to slowly disintegrate through weathering; elements like rain, ice, plants, animals, temperature and chemicals all play a part in this process. When this happens, small particles of rock and upper layer soil become sediments which then have to be moved via erosion into different locations.
Some types of weathering break apart the rocks and alter some of their minerals – this process is known as mechanical weathering and examples include expansion and contraction when a rock cools, freezing water expanding in cracks in rocks, salt wedging where crystals loosen when snowmelt melts, etc.
Other types of weathering convert solid rocks into sediments, including chemical weathering (interlocking silicate grains of granite decay along crystal boundaries); and physical weathering, where rocks disintegrate into smaller pieces due to water, wind, glaciers and gravity movement – processes which contribute to geologic cycles of erosion, deposition and compaction.
Water
Water is an inert chemical substance found throughout Earth’s hydrosphere and essential to all forms of life, making up roughly 70 percent. Water’s distinctive properties set it apart from similar substances; for instance, its polar nature results from oxygen holding a slight negative charge and hydrogen holding positive charges; this electrostatic attraction causes water molecules to form loose bonds with each other and stay together more securely than with similar substances.
Polarity also makes water an effective solvent, dissolving virtually every other molecule or ion with which it comes into contact. Nonpolar molecules like oils do not dissolve because they lack partial positive or negative charges that attract water molecules.
Erosion occurs when rock wears away, producing sediment that is transported by gravity, wind or water until reaching more gently sloping land where deposition can take place. Trees, hills and buildings may help stop this erosion process by slowing or diverting forceful moving agents such as rivers, glaciers or wind from flowing freely along their paths.