Most people are aware of erosion caused by rain, wind, or waves. Erosion is the process that breaks up and removes soil and rock particles that form sediment from our environment.
Geologists can learn a great deal from studying how sediment has been sorted. Sand grains tend to be very well sorted while clay grains tend to be poorly organized.
Water plays an essential role in weathering, erosion and deposition processes. It creates sedimentary rocks through physical weathering while chemical weathering creates minerals. Furthermore, it transports erosion-derived particles to new locations where deposition takes place.
When it rains, gravity causes water to flow downward and collect soil and other particles as it travels; this phenomenon is known as runoff; its quantity depends on factors like slope of land and number of plants present on that plot of land.
Water-running over land erodes rocks more quickly, and streams that cut through mountain ranges often form long, narrow canyons. Rivers flowing over gentler slopes tend to erode less rapidly, and tend to curve in wider loops.
Wind is another powerful force capable of contributing to erosion. It blows sand from place to place, polishing rocks and cliffs to give them a glossy, shiny surface known as desert varnish, wedge its way into cracks in rocks to form tafonis and other sculptural formations, or wedge into crevasses in rocks to form tafonis and other sculptural formations.
Weathering refers to the physical and chemical breakdown of rocks. Erosion refers to when weathered rock is carried away from its original position by wind or water currents; while deposition occurs when erosion-derived sediment deposits itself. Wind, water currents, ice flow or gravity can all play a part in erosion processes.
Rainwater seeps into cracks in rocks, expanding as it freezes, then expands further by freezing, cracking apart the rock surface and fragmenting. Frost wedging is another method ice can use to break apart rocks; repeated freezing and melting cycles of the ice creates a wedge-shaped wedge which gradually splits apart rocks over time; we can observe its effects in roads and sidewalks where ice wear has worn away parts of their surfaces.
Wind can also erode rocks by dislodging sand and other particles and transporting them to different spots, eventually creating the Great Lakes landscapes we know today. Sand on beaches may also be created this way by waves pounding on rocks; other forms of erosion such as mudslides can happen more rapidly due to movement combined with gravity.
Weathering and erosion take place wherever rocks are exposed to the elements. Although water is usually the main cause of erosion, wind can also have an effect on weathering processes. How quickly a rock erodes depends on how long it has been exposed – generally hard, rugged rock tends to weather more slowly than soft rocks.
Erosion loosens and moves weathered or unweathered solid material such as soil, sand, silt and rock fragments over time, often with wind, flowing water, waves, glaciers or gravity as the force moving it.
The constant battering of ocean waves causes erosion by wearing down pebbles and sand on beaches, gradually smoothing rough rock surfaces into shapes resembling mushrooms atop cliffs. Over time this erosion creates unique landscapes such as Scotts Bluff National Monument in Nebraska’s arches shaped by wind erosion; windblown sand also polishes rocks to give them what geologists refer to as desert varnish colors.
Plants and Animals
Physical weathering includes flowing water, salts, acids and even ice but plants and animals play a much greater role. Plant roots work their way into cracks in rocks to pry them apart through root wedging; burrowing animals may contribute to physical weathering by digging tunnels through rock. Furthermore, some plants contain substances which interact chemically with rocks and minerals to make them softer and easier to break apart; limestone for instance erodes quickly when exposed to both carbonic acid and water.
Water erosion occurs as water flows over land surfaces or down hills and mountains, washing away soil particles, rock particles and other debris from these surfaces and carrying it downstream, where it collects in river deltas to form fertile land. Sometimes this form of erosion leads to massive landslides or mass waste deposits which then collapse back onto other parts of the landscape or drift out to sea where they eventually wash up on shore or can crash against rocks and drift away into another body of water.