Protecting against erosion requires regular land inspection. Doing this can prevent small issues from turning into larger issues during rainstorms, such as mudflows.
Wind and water erode Earth’s surface, producing features such as mountain streams carving out V-shaped valleys and cliffs; also creating floodplains and river deltas in their wake.
Physical erosion of Earth’s surface involves the movement of soil and rock from one location to another – be it just meters away, such as when rocks and sand are washed down rivers, or thousands of kilometers away such as when beach sand deposits. Physical erosion may occur as a result of weathering processes as well as human activities.
Physical erosion breaks rocks into smaller chunks, or clasts. This may occur through freezing-thawing processes or through plant roots enlarging cracks gradually over time. Ocean waves also play a part in erosion processes by battering rock faces into sea stacks when receding back from cliff faces.
Clasts can then be transported by various mechanisms: wind, water, ice, gravity and the downward movement of snow are all responsible for erosion; human activities, like cutting down trees or plowing up grasses can further accelerate this process as their soil-containing product can more readily be carried away by currents of air or water.
Erosion occurs when rocks change their chemical makeup, such as iron rusting or limestone dissolving due to carbonation. This form of erosion may be faster than physical erosion.
Gravity, running water, waves, glaciers and wind can all transport material away from a site through transportive erosion – this process of carrying weathered material away is known as transportive erosion; and any particles of rock and soil carried off are known as sediment.
Rivers and glaciers form waterfalls, floodplains, and valleys by carrying sediment from one location to the next – an example of mechanical weathering. Waves can erode coastlines further by carrying away sand causing caves or arches along their course.
Plants may also contribute to physical erosion by growing and cracking rocks – a process called bioerosion. Ice can also exacerbate erosion by freezing and thawing cycles that fracture rocks into smaller pieces that are then dedeposited at new locations by deposition. Erosion may even result in mass wasting events like landslides and rockslides.
Sand, mud and other materials carried away by erosion can be distributed throughout different environments by rivers, oceans, wind and rain. Sediment that accumulates can form layers on beaches or floodplains or even at the bottom of lakes; in time these deposits bury organic matter and fossils.
Transport of sediment allows it to be sorted based on density. Beach and wind-blown deposits tend to be well sorted while stream deposits often fail this test, giving insight into energy conditions within its transporting medium.
Human land use can increase the amount of sediment entering rivers and other waterways. Logging, farming and construction sites expose or loosen soil that is easily transported by rainfall and runoff; this causes sedimentation that degrades a waterway’s ecology by decreasing instream photosynthesis while leading to increased erosion downstream.
Deposition, the movement of particles to new locations, can occur through fluid flow (streams, rivers and rain), glacier ice wedging or abrasion or wind or solution processes. Deposition can happen on timescales from seconds or minutes or hours to years or millennia – for instance beach sand carried away by storm waves is one good example, while dunes also develop over time due to deposition.
Deposition occurs when an erosion agent such as gravity, river flow, ice or wind has run out of energy to erode material from its source, such as hills. As water travels downstream it erodes hills but when it reaches flatter areas deposits the eroded soil into more stable places like riverbeds or flatlands. Deposition also takes place within caves where dead organisms skeletons may deposit themselves as chalk and coal deposits itself as the result of biological and chemical processes.