Weathering refers to the gradual transformation of Earth’s surface caused by things such as ice, water, wind and plants; erosion refers to when these changes are carried away and deposited elsewhere.
Erosion by water produces canyons, ravines and Oxbow lakes (horseshoe-shaped bends in rivers where their current moves slower than its surroundings), Alluvial Fans and deltas as a result.
Weathering
Weathering and erosion are two processes that transform Earth’s landscape over long periods. Weathering involves physical breakup of rocks at their surfaces while erosion involves moving altered rocks away from their original locations by means of water, ice, wind or gravity – leaving behind sediment that deposits itself elsewhere to form different landforms.
Weathering can be caused by several elements, including ice, salts, chemicals, plants, temperature and atmospheric changes, wind, rain and animals. The rate at which rocks breakdown depends on these variables – for instance acid rain may accelerate chemical weathering of silicate rocks.
Physical weathering processes like freeze-thaw action can rapidly disintegrate rocks, while at the same time contributing to moraines formed from retreating glaciers. Mechanical weathering occurs when animals burrow into cracks in rock, with pressure from above and below wearing away at its sides until it finally splits open into fragments.
Erosion
Over time, erosion gradually wears away at exposed rock surfaces. It depends on many factors that determine its rate of erosion – how long a surface has been exposed and its type. Some rocks such as limestone are more vulnerable than others to weathering and erosion; for instance it erodes more easily near rivers, often leaving cave systems.
Physical erosion or mechanical weathering refers to the movement of rock fragments and soil from one location to another through processes like water or wind currents; it can happen on Earth’s surface as well as subterranean regions.
Mechanical erosion can be caused by liquid water (rain, streams and lakes), ice (see Chapter 10, Mass Wasting) and wind. Plant roots as well as animals digging their own tunnels also contribute to physical erosion.
Deposition
Weathering dismantles rocks over time into smaller particles. Erosion removes these particles from their present locations and deposits them elsewhere – caused by wind, water, ice or gravity – with deposition being the process of depositing sediments like pebbles, sand and mud into new locations by natural forces such as wind, water or ice (or humans using machines) or people.
Erosion and deposition can be seen all around us every day in various forms: road cracks formed due to expansion and contraction of ice or temperature variations; waterfalls break down rock faces, waves hitting beaches create sand deposits, while erosion may occur quickly due to mudslides or flooding;
Riverine erosion and deposition is another example of this process at work. Swiftly flowing rivers can become subject to course alteration, shape change, sediment transport/deposit and the balance act between transporting sediments while depositing them resulting in fan shaped build ups known as deltas or even meander-cut lakes that form from this activity.
Landforms
Some landforms are formed gradually over time by weathering and erosion while other landforms form rapidly.
Water, ice, plants, animals and other natural agents serve as weathering agents, slowly altering Earth’s rocks into ever-evolving masterpieces such as the Grand Canyon. Erosion then transports away any bits of rock or minerals left behind.
No rock can withstand the forces of weathering and erosion, which are natural processes which wear away at mountains, carve river valleys and deposit sediment in deltas.
Deposition occurs when small bits of eroded material are deposited elsewhere, usually at the mouth of a river or ocean. Over time, these deposits may accumulate to become hills, valleys and river deltas or they could suddenly give way in a landslide. When soil deposits occur they also carry harmful chemicals into lakes and rivers which causes acid rain pollution that damages ecosystems as well as human health.