Weathering, erosion and deposition continuously shape our planet’s rocky terrain. Weathering alters rocks and minerals into more malleable forms through chemical or mechanical means; erosion then takes these more fragile pieces and deposits them elsewhere.
Water, salts, ice, plants and even animals can contribute to weathering processes in rocks. Plant roots may even find ways to gain entry through cracks and gaps between rocks to cause weathering effects.
Water
Water is often the source of rock and mineral transport. Rainwater, streams and rivers carry sediment–sand, silt and rock fragments–along with weathered rock fragments–into new locations through what’s known as erosion.
Erosion results from both physical and chemical weathering processes. Physical weathering involves breaking apart rocks through mechanical methods like rock fracturing and freeze-thaw cycles; chemical weathering entails mineral interaction with external agents like oxygen or acid to alteration products like oxygen-oxidized minerals while acid dissolves some.
Water plays a key role in the creation of most sedimentary rocks. It acts as one of the primary agents for weathering that produces mineral silicates which then become grains of sedimentary rock grains, and erosion that turns loose sediment into deposited sand and gravel deposits. Water flow speed and volume determines how much sediment is lost from erosion, with fast-flowing river waters tending to deposit coarser and less well sorted sediment than slower-moving streams and glaciers.
Wind
Wind can help break apart rocks, carry away soil particles and transport materials between locations; this process is known as deposition. Through weathering erosion and deposition processes shape Earth’s landforms and landscapes. Water, wind, glaciers (glaciers) and gravity all play their parts when it comes to weathering and erosion processes.
Erosion wears away rocks over long periods of time. It can occur quickly during a landslide or slowly over thousands of years like what happened with the Grand Canyon being formed by erosion from Colorado River’s slow erosion of rock layers.
Breakdown of rocks may occur through biological, chemical or mechanical means. Plant roots often enter cracks in rocks through biological weathering while chemical weathering uses rainwater with chemicals that alter minerals found in rocks. Physical weathering includes both mechanical erosion as well as glacial transport of pieces of rock along the ground surface.
Ice
Rocks exposed to the elements at Earth’s surface experience dramatic transformation. Temperature changes, pressure reduction, and moisture build-up all lead to profound transformation.
Ice is an indispensable agent of weathering erosion. Glaciers move slowly across the land, slowly chipping away at rocks and soil they come across, shaping its landscape with debris such as large boulders, pebbles, and silt, all dropped by melting glaciers; their deposits form moraines.
Ice can also cause chemical weathering. Water that seeps into cracks of a rock may freeze as temperatures decrease and expand and force its way through, splitting the rock. Plant growth also contributes to physical erosion by forcing its way into small crevices through root wedges that wedge their way in via bioerosion or through river currents and wind, leading to bioerosion or deposition as these materials travel elsewhere – these processes being known respectively as bioerosion or deposition.
Gravity
Gravity works to wear away and move particles on Earth’s surface, leading to erosion. Deposition can either take place locally, such as beach deposits of sand, or spread far and wide as sediment travels with flowing water or glacial ice to sites where it will eventually settle out as sediment deposits itself on land surface or becomes trapped under glacial ice cover.
Gravity has an enormous influence on erosion, from direct landslides and mudslides reshaping mountains or hills, to indirect effects such as pulling rain towards Earth, drawing floodwaters downward, and pulling glaciers downhill. Weathering increases rock surface area for chemical weathering to take place over time.
Erosion is an ongoing process on Earth that shapes many of its spectacular landforms, yet can be dangerous when riverbank erosion releases chemicals and pollutants into nearby waters, which is often the case during mining operations where chemical erosion of rock and soil can lead to environmental harm.