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How does Erosion Affect the Environment?

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How does Erosion Affect the Environment?

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No ecosystem is entirely free of sediment. In aquatic environments, its presence can threaten the health of ecosystems. Sediment can cloud the water, which in turn can negatively impact the plants and animals of these places. Also, depending upon the type of sediment, additional issues can also occur. It can have both organic and inorganic sources, whether it is algae floating in the water or suspended particles of soil from an eroded shoreline.

One of the primary negative effects of sediment in the ecosystem concerns the nature of the sediment. Agricultural and urban runoff may contain toxic materials, which can damage or even kill the organisms within an ecosystem. According to the U.S. Environmental Protection Agency (EPA), runoff from farmlands is the main cause of pollution in U.S. waterways. The runoff can include sediment from pesticide and fertilizer applications as well as animal waste and bacteria.

Some animal species are especially sensitive to the effects of sediment, with contamination quickly accumulating in animal tissues. Filter feeders such as mussels and clams get food by filtering water through their bodies, making them especially vulnerable to the presence of sediment. Other species such as salmon require clear waters in order to locate their prey. High levels of suspended sediment can interfere with their ability to find food, risking the health of the ecosystem by disrupting the prey-predator relationships.

Wetlands affect the sediment load in the ecosystem by slowing water flow, which allows suspended particles to drop down to ground level. This filtering action is an important environmental benefit because it removes the sediment from the water. In essence, the sediment, whether it contains contaminants or not, becomes locked into the sediment layer of the wetlands. The effects of the pollutants are then mitigated.

One way in which sediment enters an ecosystem is through soil erosion. Water flowing over bare soils will easily dislodge sediment, where it will later be deposited within the environment. Impervious surfaces, such as roads and parking lots, facilitate soil erosion. Without plants to slow it, water flow increases, allowing it to dig deeply into stream banks.

The best way to control the negative environmental effects of sediment is to prevent its introduction into the environment. Planting dense groundcover along stream banks and coastal areas will help keep soils intact and prevent them from washing away. Restoration of wetlands within floodplains and other areas will improve water quality by removing suspended sediment from the water.

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No ecosystem is entirely free of sediment. In aquatic environments, its presence can threaten the health of ecosystems. Sediment can cloud the water, which in turn can negatively impact the plants and animals of these places. Also, depending upon the type of sediment, additional issues can also occur.

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Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering, breaks down or dissolves rock, but does not involve movement. Erosion is the opposite of deposition, the geological process in which earthen materials are deposited, or built up, on a landform. Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier). If the wind is dusty, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid (air or water) and being transported from one place to another. This transported material is called sediment.

Physical erosion describes the process of rocks changing their physical properties without changing their basic chemical composition. Physical erosion often causes rocks to get smaller or smoother. Rocks eroded through physical erosion often form clastic sediments. Clastic sediments are composed of fragments of older rocks that have been transported from their place of origin. Landslides and other forms of mass wasting are associated with physical weathering. These processes cause rocks to dislodge from hillsides and crumble as they tumble down a slope.

Plant growth can also contribute to physical erosion in a process called bioerosion. Plants break up earthen materials as they take root, and can create cracks and crevices in rocks they encounter. Ice and liquid water can also contribute to physical erosion as their movement forces rocks to crash together or crack apart. Some rocks shatter and crumble, while others are worn away. River rocks are often much smoother than rocks found elsewhere, for instance, because they have been eroded by constant contact with other river rocks.

Erosion by Water

Liquid water is the major agent of erosion on Earth. Rain, rivers, floods, lakes, and the ocean carry away bits of soil and sand and slowly wash away the sediment. Rainfall produces four types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.

Splash erosion describes the impact of a falling raindrop, which can scatter tiny soil particles as far as 0.6 meters (two feet).

Sheet erosion describes erosion caused by runoff.

Rill erosion describes erosion that takes place as runoff develops into discrete streams (rills).

Finally, gully erosion is the stage in which soil particles are transported through large channels.

The Fish River Canyon, in southern Namibia, is the largest canyon in Africa and a product of valley erosion. Over millions of years, the Fish River wore away at the hard gneiss bedrock, carving a canyon about 160 kilometers (99 miles) in length, 27 kilometers (17 miles) wide, and 550 meters (1,084 feet) deep.

The battering force of ocean waves also erodes seaside cliffs. The action of erosion can create an array of coastal landscape features. For example, erosion can bore holes that form caves. When water breaks through the back of the cave, it can create an arch. The continual pounding of waves can cause the top of the arch to fall, leaving nothing but rock columns called sea stacks. The seven remaining sea stacks of Twelve Apostles Marine National Park, in Victoria, Australia, are among the most dramatic and well-known of these features of coastal erosion.

Erosion by Wind

Erosion by Ice

Ice, usually in the form of glaciers, can erode the earth and create dramatic landforms. In frigid areas and on some mountaintops, glaciers move slowly downhill and across the land. As they move, they transport everything in their path, from tiny grains of sand to huge boulders. Rocks carried by glaciers scrape against the ground below, eroding both the ground and the rocks. In this way, glaciers grind up rocks and scrape away the soil. Moving glaciers gouge out basins and form steep-sided mountain valleys. Eroded sediment called moraine is often visible on and around glaciers.

Several times in Earth's history, vast glaciers covered parts of the Northern Hemisphere. These glacial periods are known as ice ages. Ice Age glaciers carved much of the modern northern North American and European landscape. Ice Age glaciers scoured the ground to form what are now the Finger Lakes in the U.S. state of New York, for example. They carved fjords, deep inlets along the coast of Scandinavia. The snout of a glacier eroded Cape Cod Bay, Massachusetts, U.S., and formed the recognizable fishhook shape of Cape Cod itself.

Today, in places such as Greenland and Antarctica, glaciers continue to erode the earth. Ice sheets there can be more than a mile thick, making it difficult for scientists to measure the speed and patterns of erosion. However, ice sheets do erode remarkably quickly-as much as half a centimeter (0.2 inch) every year.

Other Forces of Erosion

Factors Impacting Erosion

Some of the natural factors impacting erosion in a landscape include climate, topography, vegetation, and tectonic activity. Climate is perhaps the most influential force impacting the effect of erosion on a landscape. Climate includes precipitation and wind. Climate also includes seasonal variability, which influences the likelihood of weathered sediments being transported during a weather event such as a snowmelt, breeze, or hurricane. Topography, the shape of surface features of an area, can contribute to how erosion impacts that area. The earthen floodplains of river valleys are much more prone to erosion than rocky flood channels, which may take centuries to erode. Soft rock like chalk will erode more quickly than hard rocks like granite.

Vegetation can slow the impact of erosion. Plant roots adhere to soil and rock particles, preventing their transport during rainfall or wind events. Trees, shrubs, and other plants can even limit the impact of mass wasting events such as landslides and other natural hazards such as hurricanes. Deserts, which generally lack thick vegetation, are often the most eroded landscapes on the planet.

Finally, tectonic activity shapes the landscape itself, and thus influences the way erosion impacts an area. Tectonic uplift, for example, causes one part of the landscape to rise higher than others. In a span of about 5 million years, tectonic uplift caused the Colorado River to cut deeper and deeper into the Colorado Plateau, land in what is now the U.S. state of Arizona. It eventually formed the Grand Canyon, which is more than 1,600 meters (one mile) deep and as much as 29 kilometers (18 miles) wide in some places.

Erosion and People
Deposition, Soils, and Sediments
Eroded sediments have profoundly influenced the development of civilizations around the world. Agricultural development is often reliant on the nutrient-rich soils created by the accumulation of eroded earth. When the velocity of wind or water slows, eroded sediment is deposited in a new location. The sediment builds up in a process called sedimentation and creates fertile land. River deltas are made almost entirely of sediment that has eroded from the banks and bed of a river.

The rich delta soils of the San Joaquin and Sacramento rivers in northern California, for example, have created one of the most agriculturally productive areas in the world. Loess is an agriculturally rich sediment made almost entirely of wind-blown, eroded sediment.

The Yellow River in central China gets its name from the yellow loess blown into and suspended in its water. The fertile lands around the Yellow River have been among China's most productive for thousands of years.

Erosion is a natural process, but human activity can make it happen more quickly. Human activity altering the vegetation of an area is perhaps the biggest human factor contributing to erosion. Trees and plants hold soil in place. When people cut down forests or plow up grasses for agriculture and development, the soil is more vulnerable to washing or blowing away. Landslides become more common. Water rushes over exposed soil rather than soaking into it, causing flooding.

The rise in temperature is also quickly melting glaciers. The slower, more massive form of glacial erosion is being supplanted by the cumulative impact of rill, gully, and valley erosion. In areas downstream from glacial snouts, rapidly melting glaciers are contributing to sea level rise. The rising sea erodes beaches more quickly.

Erosion control is the process of reducing erosion by wind and water. Farmers and engineers must regularly practice erosion control. Sometimes, engineers simply install structures to physically prevent soil from being transported. Gabions are huge wireframes that hold boulders in place, for instance. Gabions are often placed near cliffs. These cliffs, often near the coast, have homes, businesses, and highways near them. When erosion by water or wind threatens to tumble the boulders toward buildings and cars, gabions protect landowners and drivers by holding the rocks in place.

Living shorelines are another form of erosion control in wetland areas. Living shorelines are constructed by placing native plants, stone, sand, and even living organisms such as oysters along wetland coasts. These plants help anchor the soil to the area, preventing erosion. By securing the land, living shorelines establish a natural habitat. They protect coastlines from powerful storm surges as well as erosion.

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Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water.

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The process known as weathering breaks up rocks so that they can be carried away by the process known as erosion. Water, wind, ice, and waves are the agents of erosion that wear away at the surface of the Earth.

Water Erosion

Water is the most important erosional agent and erodes most commonly as running water in streams. However, water in all its forms is erosional. Raindrops (especially in dry environments) create splash erosion that moves tiny particles of soil. Water collecting on the surface of the soil collects as it moves towards tiny rivulets and streams and creates sheet erosion.

In streams, water is a very powerful erosional agent. The faster water moves in streams the larger objects it can pick up and transport. This is known as critical erosion velocity. Fine sand can be moved by streams flowing as slowly as three-quarters of a mile per hour.

Streams erode their banks in three different ways: 1) the hydraulic action of the water itself moves the sediments, 2) water acts to corrode sediments by removing ions and dissolving them, and 3) particles in the water strike bedrock and erode it.

The water of streams can erode in three different places: 1) lateral erosion erodes the sediment on the sides of the stream channel, 2) down cutting erodes the stream bed deeper, and 3) headward erosion erodes the channel upslope.

Wind Erosion

Erosion by wind is known as aeolian (or eolian) erosion (named after Aeolus, the Greek god of winds) and occurs almost always in deserts. Aeolian erosion of sand in the desert is partially responsible for the formation of sand dunes. The power of the wind erodes rock and sand.

Ice Erosion

The erosive power of moving ice is actually a bit greater than the power of water but since water is much more common, it is responsible for a greater amount of erosion on the earth's surface.

Glaciers can perform erosive functions - they pluck and abrade. Plucking takes place by water entering cracks under the glacier, freezing, and breaking off pieces of rock that are then transported by the glacier. Abrasion cuts into the rock under the glacier, scooping rock up like a bulldozer and smoothing and polishing the rock surface.

Wave Erosion

Waves in oceans and other large bodies of water produce coastal erosion. The power of oceanic waves is awesome, large storm waves can produce 2000 pounds of pressure per square foot. The pure energy of waves along with the chemical content of the water is what erodes the rock of the coastline. Erosion of sand is much easier for the waves and sometimes, there's an annual cycle where sand is removed from a beach during one season, only to be returned by waves in another.

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Learn About the Agents of Erosion and How the Elements Erode the Earth

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The process known as weathering breaks up rocks so that they can be carried away by the process known as erosion. Water, wind, ice, and waves are the agents of erosion that wear away at the surface of the Earth.

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The formation of river rocks requires moving water and smaller rocks. Rocks easily eroded by water more likely form river rocks. Typical rocks with jagged edges can fall into the bottom of a river or stream bed or remain on the river bank. The speed of the river determines how quickly the rock becomes a river rock.

In the river, water flows constantly over the rocks. The movement of water itself does not weather the rocks, but that water carries with it smaller pieces of rocks, sediment and silt with it. These tiny bits of broken stones hit the rocks at the bottom of the river, breaking off pieces of them, which the river carries away. The faster the water moves, the more sediment flows over the river rocks, hastening weathering.

Erosion occurs when the pieces broken from the rock get carried away by the river. These bits of rock create the sand and silt along the river banks and at the mouth of the river. Eventually, a narrow stream widens into a large river. This slows the speed of the water, and some of the broken pieces of river rocks (sediment) fall to the bottom of the river bed. River deltas form in this way when the water from a river moves very slowly at its mouth where it flows into a larger body of water.

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The formation of river rocks requires moving water and smaller rocks. Rocks easily eroded by water more likely form river rocks. Typical rocks with jagged edges can fall into the bottom of a river or stream bed or remain on the river bank. The speed of the river determines how quickly the rock becomes a river rock.

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How do glaciers shape the landscape? Animation from geog.1 Kerboodle.

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Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.

Subjects

Earth Science, Geology, Geography, Physical Geography

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmarks such as the Grand Canyon, in the U.S. state of Arizona. This massive canyon is 446 kilometers (277 miles) long, as much as 29 kilometers (18 miles) wide, and 1,600 meters (1 mile) deep. Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water. As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess, and alluvial sediments. Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering, in which living or once-living organisms contribute to weathering, can be a part of both processes. Mechanical Weathering Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. If temperatures drop low enough, the water will freeze. When water freezes, it expands. The ice then works as a wedge. It slowly widens the cracks and splits the rock. When ice melts, liquid water performs the act of erosion by carrying away the tiny rock fragments lost in the split. This specific process (the freeze-thaw cycle) is called frost weathering or cryofracturing. Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again, the structure of the rock weakens. Over time, it crumbles. Rocky desert landscapes are particularly vulnerable to thermal stress. The outer layer of desert rocks undergo repeated stress as the temperature changes from day to night. Eventually, outer layers flake off in thin sheets, a process called exfoliation. Exfoliation contributes to the formation of bornhardts, one of the most dramatic features in landscapes formed by weathering and erosion. Bornhardts are tall, domed, isolated rocks often found in tropical areas. Sugarloaf Mountain, an iconic landmark in Rio de Janeiro, Brazil, is a bornhardt. Changes in pressure can also contribute to exfoliation due to weathering. In a process called unloading, overlying materials are removed. The underlying rocks, released from overlying pressure, can then expand. As the rock surface expands, it becomes vulnerable to fracturing in a process called sheeting. Another type of mechanical weathering occurs when clay or other materials near rock absorb water. Clay, more porous than rock, can swell with water, weathering the surrounding, harder rock. Salt also works to weather rock in a process called haloclasty. Saltwater sometimes gets into the cracks and pores of rock. If the saltwater evaporates, salt crystals are left behind. As the crystals grow, they put pressure on the rock, slowly breaking it apart. Honeycomb weathering is associated with haloclasty. As its name implies, honeycomb weathering describes rock formations with hundreds or even thousands of pits formed by the growth of salt crystals. Honeycomb weathering is common in coastal areas, where sea sprays constantly force rocks to interact with salts. Haloclasty is not limited to coastal landscapes. Salt upwelling, the geologic process in which underground salt domes expand, can contribute to weathering of the overlying rock. Structures in the ancient city of Petra, Jordan, were made unstable and often collapsed due to salt upwelling from the ground below. Plants and animals can be agents of mechanical weathering. The seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces. Over time, trees can break apart even large rocks. Even small plants, such as mosses, can enlarge tiny cracks as they grow. Animals that tunnel underground, such as moles and prairie dogs, also work to break apart rock and soil. Other animals dig and trample rock aboveground, causing rock to slowly crumble. Chemical Weathering Chemical weathering changes the molecular structure of rocks and soil. For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation. This produces a weak acid, called carbonic acid, that can dissolve rock. Carbonic acid is especially effective at dissolving limestone. When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves. Carlsbad Caverns National Park, in the U.S. state of New Mexico, includes more than 119 limestone caves created by weathering and erosion. The largest is called the Big Room. With an area of about 33,210 square meters (357,469 square feet), the Big Room is the size of six football fields. Sometimes, chemical weathering dissolves large portions of limestone or other rock on the surface of the Earth to form a landscape called karst. In these areas, the surface rock is pockmarked with holes, sinkholes, and caves. One of the world's most spectacular examples of karst is Shilin, or the Stone Forest, near Kunming, China. Hundreds of slender, sharp towers of weathered limestone rise from the landscape. Another type of chemical weathering works on rocks that contain iron. These rocks turn to rust in a process called oxidation. Rust is a compound created by the interaction of oxygen and iron in the presence of water. As rust expands, it weakens rock and helps break it apart. Hydration is a form of chemical weathering in which the chemical bonds of the mineral are changed as it interacts with water. One instance of hydration occurs as the mineral anhydrite reacts with groundwater. The water transforms anhydrite into gypsum, one of the most common minerals on Earth. Another familiar form of chemical weathering is hydrolysis. In the process of hydrolysis, a new solution (a mixture of two or more substances) is formed as chemicals in rock interact with water. In many rocks, for example, sodium minerals interact with water to form a saltwater solution. Hydration and hydrolysis contribute to flared slopes, another dramatic example of a landscape formed by weathering and erosion. Flared slopes are concave rock formations sometimes nicknamed "wave rocks." Their c-shape is largely a result of subsurface weathering, in which hydration and hydrolysis wear away rocks beneath the landscape's surface. Living or once-living organisms can also be agents of chemical weathering. The decaying remains of plants and some fungi form carbonic acid, which can weaken and dissolve rock. Some bacteria can weather rock in order to access nutrients such as magnesium or potassium. Clay minerals, including quartz, are among the most common byproducts of chemical weathering. Clays make up about 40% of the chemicals in all sedimentary rocks on Earth. Weathering and People Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering. Burning coal, natural gas, and petroleum releases chemicals such as nitrogen oxide and sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments. For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world's largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion. But in recent years, acid rain has turned the statue's nose black and made some of its hair crumble and fall.

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National Geographic Society

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Last Updated

October 19, 2023

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Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering.

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The Earth's surface gets broken down through weathering.

Small pieces of the Earth get moved through erosion.

The small pieces are deposited somewhere else through a process called deposition.

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Learn about weathering, erosion & deposition! Our science video for kids teaches you how these forces of nature shape the surface of the earth! Watch now!

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Ohio would not be what it is today without the impact of the glaciers.

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This is a short article about the difference between weathering and erosion

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​ Weathering​ and ​ erosion ​ are processes by which rocks are broken down and moved from their original location. The difference between weathering and erosion is based on whether a rock's location has changed: Weathering degrades a rock without moving it, while erosion carries rocks and soil away from their original locations. Weathering often leads to erosion by causing rocks to break down into smaller pieces, which erosive forces can then move away.

TL;DR (Too Long; Didn't Read)

Weathering and erosion are sometimes use interchangeably, but they're different. ​ Weathering​ breaks large rocks into smaller pieces, while ​ erosion ​ moves those pieces away from the original rock.

The main difference between weathering and erosion lies in where the process takes place. Weathering degrades a rock without changing its location. Erosion, on the other hand, causes rocks - or particles of rock - to be carried away from their original locations and deposited elsewhere. Weathering often leads to erosion, breaking down the rock into small pieces that are easier for wind and water to carry away.

​ Wind abrasion ​ is an example of a process that includes both weathering and erosion. Wind picks up small pieces of rock and blows them against larger stones, causing small particles of the larger formations to break off - this is weathering. The same wind picks up these particles and takes them away from the rock they broke off of - this is erosion.

There are two distinct types of weathering, which alter and degrade rock in different ways. ​ Physical weathering ​ breaks down a rock's physical structure. For example, in cold environments water that gets into holes in rock and freezes will cause those holes to expand and eventually crack and split the rock.

The same process may be caused by salt buildup or growing tree roots. Another form of physical weathering occurs when wind or water causes rocks to rub against each other, smoothing their surfaces.

​ Chemical weathering ​ changes the chemical structure of rock, causing it to become softer or more brittle. For example, iron in a rock might react with oxygen to form easily degradable rust, or acids in rainwater may remove calcium from limestone and marble. Chemical weathering often precedes physical weathering, making rocks more vulnerable to forces like wind and rain.

Different types of erosion are usually differentiated by the force that carries rock, stone or soil away from its location. Water is the most common force that causes erosion. Rivers wear down and carry away rock and soil along their banks. The Grand Canyon was formed from millions of years of this sort of erosion. Similar erosion occurs in the ocean, where moving water and waves degrade and carry away particles of coastline rock.

Wind erosion can only occur on smaller particles of ash, dust and rock, but it can still move large quantities of these particles from their original locations and create impressive formations, such as sand dunes.

Erosion by ice is rare in most parts of the world, but ice can move much larger rocks than most other erosive forces. Ice may carry huge boulders miles away from their original locations.

​ Mass wasting ​ is a specific type of erosion that is caused by gravity. Mass wasting occurs when soil or rocks are carried away - not by wind or water - but by falling or sliding downwards.

A ​ rockslide​ or ​ landslide​ is a common example of mass wasting, as a large quantity of loose rock or soil rolls or slides down a slope. ​ Rock falls ​ occur when loose rock splits off from high cliffs. Mass wasting may also cause physical weathering by causing rocks to shatter upon hitting the ground or causing rocks to rub against each other while rolling and sliding.

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The Difference Between Weathering & Erosion

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Weathering and erosion are sometimes use interchangeably, but they're different. The difference between weathering and erosion has to do with location: Weathering breaks large rocks into smaller pieces without moving the rock, while erosion moves the pieces of rock away from their original location.

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Difference between Weathering and Erosion

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Weathering is the process by which rocks are broken down. Weathering agents can be wind, water, freezing & thawing (see the Exfoliation video on the right), glaciers, chemicals (such as acid rain),…

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Chemical Weathering Demo

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When materials like rocks and soil on the Earth's surface wear down to sand and gravel or move from one location to another, erosion is the main culprit. Landforms, like canyons, often get their shape as a direct result of erosion. Given enough time, water and ice can even cut through solid rock. But the most powerful force behind erosion is gravity. Gravity causes chunks of rock to fall from mountains and pulls glaciers downhill, cutting through solid stone. This kind of erosion -- gravitational erosion -- shapes the surface of the Earth as we know it.

TL;DR (Too Long; Didn't Read)

Gravitational erosion describes the movement of soil or rock due to the force of gravity. Gravity impacts erosion in direct ways like landslides, mudslides and slump. It can also impact erosion in indirect ways, by pulling rain to the Earth and forcing glaciers downhill.

Gravitational erosion represents the movement of soil or rock from one place to another due to gravity's pull. When chunks of stone fall from a mountainside to the ground below, it is because gravity pulled them down. When a glacier moves through a mountain range, slowly flattening or carving the Earth's surface in that area, it is because the pull of gravity forces the glacier downhill. When mudslides or landslides occur, smoothing the sides of mountains or large hills, the gravity is at work.

Even though geologists recognize water and ice as the biggest agents of erosion, it is the force of gravity that powers them both.

Gravity impacts erosion in both direct and indirect ways. Direct impacts of the power of gravity include rocks, mud or soil moving downhill. No other agent, such as water or ice, is directly involved in these actions. Instead, gravity works alone to cause erosion.

Landslides often occur as a direct result of gravitational erosion. When soil loosens suddenly, due to another agent, like high winds or earthquakes, rocks and soil tumble downhill because of gravity's power. These materials gather momentum as they fall, causing more soil and rocks to tumble downhill right along with them. Landslides can drastically reshape the sides of hills or mountains any time they occur.

Gravitational erosion can also directly result in mudslides. When mud, formed high atop a hill or mountain, suddenly pulls away to slide downhill, once again the power of gravity is responsible. A mass of moving mud can wash away large amounts of soil as it streams atop soil's surface, and often dislodges rocks and even large boulders. If a mudslide is large enough, it can lead to dramatic, immediate changes in the shape of hills or mountainsides.

Gravity can also directly cause a phenomenon known as slump, in which large chunks of rock and soil suddenly break off and fall from the side of a hill or mountain. Unlike a landslide, rocks and soil no not roll down the side of a such landforms, but instead fall directly to the Earth below. This is how large chunks of mountains and hills can change shape because of slump.

As two of the best-known agents of erosion, neither water nor ice could cause erosion without gravity's help. Gravity's indirect impacts on erosion include pulling rain to the Earth, drawing floodwaters downward and dragging glaciers downhill.

Rain slowly wears down the surfaces of mountains, hills and other landforms with time, but rain does not reach Earth's surface on its own. Rain forms in clouds when water vapor condenses, and gravity pulls it to Earth. Over time, rain loosens soil and the wind blows it away, or the rain creates mud, which typically moves from the highest to lowest points down the side of a mountain or hill. Rain can also wear rocks down with time, though this process often takes millions of years to drastically reshape large landforms.

Glaciers are some of the most powerful agents of erosion. These giant formations of ice and snow moving across different parts of the Earth at different points in history, continue to do so today. Several million years ago, scientists postulated that glaciers moved across parts of North America, causing major geological changes in what is now the Midwestern United States. Yosemite Valley, located along California's Sierra Nevada mountain range in Yosemite National Park, got its shape when glaciers cut through the range's massive granite, leaving stunning and world-renown features like the sheered off rock-face of Half Dome and the massive El Capitan. Glaciers' slow and steady movement even flattened certain areas in modern-day Indiana with only a few gorges and elevated landforms left intact.

Glaciers move with the help of gravity. Over long periods of time, the pull of gravity forces them toward lower elevations. Glaciers freeze the land around them, then unfreeze a bit, just enough to move further downhill before freezing again. As this process occurs, glaciers break soil and rock apart, pulling them along while often scratching grooves into the bedrock beneath. Because of this, glaciers continually accumulate mass in the form of frozen dirt and rock, making them heavier. Thanks to gravity, the heavier a glacier becomes, the quicker it moves, and the more impact it has upon the land.

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When materials like rocks and soil on the Earth's surface wear down to sand and gravel or move from one location to another, erosion is the main culprit. Landforms, like canyons, often get their shape as a direct result of erosion. Given enough time, water and ice can even cut through solid rock.

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Weathering and Erosion: Crash Course Kids #10.2