Erosion is the gradual wear-and-tear of Earth’s surface by natural forces. Erosion forms mountain peaks and valleys as well as beaches and sand dunes.
Water is the main agent of erosion, flowing in rivers and forming streams to carry rocks and soil downstream. Gravity also plays a part, pulling mountainside down or creating landslides as an agent of change.
Water
Water erosion occurs when moving streams or rivers collect and transport rock and sediment particles. This often happens as weathering breaks down solid rock into fragments that can easily be transported by water currents.
Erosion rates depend on factors like water flow speed, rock size and shape, slope of land surface and climate; areas experiencing more rain, severe thunderstorms and less vegetation cover typically experience greater erosion rates.
Water is the primary agent of erosion. Most erosion occurs when water scourges through soil, picking up and carrying away sediment particles that settle, then is carried off by gravity or wind. Living shorelines using native plants, sand and oyster shells to stabilize coastal regions may help mitigate erosion by anchoring soil to provide habitats for small animals; however, cutting back vegetation may only accelerate it by eliminating natural protection provided by plant roots that helps slow water flow.
Wind
Wind erosion is one of the primary sources of erosion. Wind picks up loose soil particles and transports them by suspension, saltation and surface creep – often breaking them up during contact rubbing against hard materials such as rock. As they rub against them and break them up they cause rock or material erode by rubbing against each other and wearing away at them, creating sand dunes on beaches or deserts, gravel deposits along rivers or lakes and shaping mountains and valleys along their route.
Human activities can hasten erosion by cutting down trees, overgrazing cattle, and other human actions. Erosion is most rapid where plants have been destroyed to expose exposed soil. Without vegetation to hold onto it, more soil may wash away with each wash of wind or rain – leading to billions in annual losses of valuable topsoil created over many decades that costs billions in lost profits each year.
Gravity
Gravity works together with water, wind and ice to erode certain areas. For example, rivers that flow downstream can gather rock fragments, soil particles and debris as they travel. Over time, these particles wear away at riverbank sides before depositing them at canyon bottoms or along shorelines.
Wind also contributes to erosion by lifting loose sand and dust from dry land and carrying it away, sometimes for hundreds of miles – as seen when bits of desert soil from northern Chad are transported all the way to Brazil by wind currents.
Gravity can cause erosion quickly, as seen with sudden movements of rocks and earth known as landslides or avalanches, while in other instances, materials move more gradually over time; examples include slumps or mudflows. To slow or prevent erosion, planting trees and other forms of vegetation, building retaining walls and keeping drainage channels free are all effective means.
Ice
Ice is one of the most powerful forces used to erode rocks. Glaciers can sculpt landscapes into stunning forms, forming corries, aretes and pyramidal peaks. Frozen-thaw weathering uses water seeping into cracks in rocks before freezing and expanding over time to weaken it and make eroding easier.
Glaciers move across rocks they carry, scraping against them to create glacial striations marks – these scratch marks can erode away and leave behind permanent evidence of glacier action on particularly steep mountains.
Glacial erosion is also responsible for creating various other landforms such as ribbon lakes, truncated spurs and U-shaped valleys. You can learn more about them with this collection of resources.