Erosion

Wind and water move the earth.

Rain can wash soil away. A falling raindrop hits the ground. It makes a small hole. This moves tiny bits of dirt.

Water flows down hills. It can make small paths. These paths can grow deep. This is called erosion.

Waves hit the shore. They break rocks into pieces. This makes sand and small stones.

Ice can also move earth. Big sheets of ice scrape the ground. This changes the land. Erosion is a part of our world.

Erosion is a way the Earth changes. It happens when water, wind, or ice move soil and rock. These materials move from one place to another. This is different from weathering. Weathering breaks things down, but it does not move them.

Rain can cause many types of erosion. First, a raindrop hits the soil. This is splash erosion. It makes small holes and kicks up dirt. Next, water flows over the land in a thin layer. This is sheet erosion. If the water forms small paths, it is called rill erosion.

If the paths become very deep, they are called gullies.

Rivers also move earth. Fast water can wear away the banks of a river.

In some places, moving water melts frozen ground. This is called thermal erosion.

At the coast, waves hit the cliffs. This can break rocks into pieces. Waves also throw sand and stones against the cliffs. This is called abrasion.

Even big glaciers can erode the land. They scrape the ground as they move.

Erosion is a way the Earth's surface changes over time. It happens when things like water, wind, or ice move soil and rock from one place to another. This is different from weathering, which breaks materials down but does not move them.

Once material is moved, it is left in a new spot through a process called deposition. Erosion can happen over very small distances or across thousands of kilometers. It is a natural part of our world, but it can also change landscapes very quickly.

Rainfall creates several steps of erosion on the ground. It often starts with splash erosion, where a falling raindrop hits the soil and creates a small crater.

Next comes sheet erosion, where water flows over the land in a thin layer. If the water forms small, shallow paths, it is called rill erosion.

If these paths become very deep and wide, they are known as gullies. Gullies are large enough that they cannot be fixed by normal farming tools. Extreme gully erosion can even create strange landscapes called badlands.

Rivers and streams are also powerful tools for moving earth. As water flows, it can wear away the banks of a river or deepen the valley floor.

In some cold places, moving water can melt frozen ground, which is called thermal erosion. This happened at the Lena River in Siberia, where banks made of permafrost slumped away.

On a river bend, the water moves faster on the sharp side, causing it to erode away. On the wider, slower side, material often builds up instead. Glaciers also erode the land by scraping the ground as they move.

At the coast, the ocean uses many methods to reshape the land. Waves can hit a cliff and trap air in cracks, which helps break the rock.

This is called hydraulic action. Waves also throw sand and stones against cliffs, a process known as abrasion.

Some rocks even dissolve in seawater, which is a type of chemical erosion. This can create features like sinkholes in certain landscapes. Even living things can contribute to this through bioerosion, where they scrape or grind the rock.

While erosion is natural, human activities have made it happen much faster. Global soil erosion has increased by 10 to 40 times because of people.

In the Appalachian Mountains, intensive farming has caused erosion at up to 100 times the natural rate. Activities like deforestation, building roads, and urban sprawl all speed up this process. This can lead to problems like losing healthy soil for plants or clogging waterways with sediment. Protecting the land is a hard job, but there are ways to limit how much soil is lost.

Erosion is the process of removing material from one location on the Earth's crust. This material can be soil, rock, or even dissolved substances. Once removed, these materials are transported to a new location. This second step is known as deposition, where the material is finally placed down. It is important to distinguish erosion from weathering. Weathering involves breaking materials down, but it does not involve movement. Erosion, however, relies on movement by agents like water, wind, or ice.

Physical erosion occurs when rock or soil is moved as clastic sediment. This is different from chemical erosion. In chemical erosion, material is removed through dissolution, which means it dissolves into a liquid. The agents that drive these processes are varied. Rainfall and surface runoff are major drivers on land. Rivers can wear down bedrock through constant flow. Coastal areas face erosion from sea waves and currents. Glaciers move through processes like plucking and abrasion. Wind and groundwater also play significant roles in reshaping the surface.

Rainfall creates a specific sequence of soil erosion stages. The first stage is splash erosion. This happens when a falling raindrop hits the soil and creates a small crater. This impact ejects soil particles into the air. If the rain continues, sheet erosion may follow. This is the transport of loosened particles by a thin layer of overland flow. If water gathers into small, shallow paths, it becomes rill erosion. Rills are ephemeral, meaning they are temporary, concentrated flow paths.

The final and most severe stage of water erosion is gully erosion. Gullies form when runoff accumulates and flows rapidly through narrow channels. These channels are deep enough that they cannot be fixed by normal tillage. Extreme gully erosion can lead to the formation of badlands. Badlands occur in areas with high relief and easily eroded bedrock. This often happens in climates where protective vegetation cannot grow.

Rivers and streams also reshape the landscape through distinct mechanisms. Valley erosion occurs as water flows along a linear feature. This process deepens the valley and extends it into the hillside. In early stages, valleys often have a V-shaped cross-section. As the stream reaches a base level, lateral erosion begins. This widens the valley floor and creates a floodplain. During floods, erosion is much more intense. Water carries sediment using traction, where pebbles and boulders scrape the surface.

Coastal erosion is driven by several powerful hydraulic and mechanical forces. Hydraulic action occurs when waves compress air inside rock joints, causing cracks. Wave pounding happens when the sheer energy of a wave breaks pieces off. Abrasion, or corrasion, occurs when waves launch sediment against a cliff. This is often the most rapid form of shoreline erosion. Additionally, corrosion involves the dissolving of rock by carbonic acid in seawater. Some organisms even contribute to this through bioerosion, which is the scraping or grinding of rock.

While erosion is a natural cycle, human activity has greatly accelerated it. Human activities have increased the global rate of soil erosion by 10 to 40 times. In the Appalachian Mountains, intensive farming has caused erosion at 100 times the natural rate. Deforestation, road building, and urban sprawl also stimulate these processes. Excessive erosion leads to "on-site" problems like the loss of nutrient-rich soil. This can cause ecological collapse or desertification. "Off-site" problems include the sedimentation of waterways and the damage of roads.

Understanding these processes helps scientists manage the environment. Water and wind erosion are the primary causes of land degradation. Together, they are responsible for about 84% of the world's degraded land. This makes excessive erosion one of the most significant environmental issues today. By studying how sediment moves, we can find ways to protect vulnerable soils. Many prevention and remediation practices exist to help limit this damage.