What Forces Can Erode Rocks?

Gravity

• Gravity causes mass movement, which includes mudflows, landslides or slump. Each of these movements weathers rocks and causes them to break away form the earth's surface. Landslides, for instance, occur when soil and rock slide down a steep hill or slope. Sometimes large amounts of rock fall during landslides. Mudslides happen when a mixture of soil, water and rock flow downhill; they typically occur during heavy rains or after an earthquake. Slumps occur when water soaks a base of a slope that is rich in soil and clay. This causes a large mass of rock and soil to break away, causing the slope to look as though part of its bottom was pulled out from underneath it.

Water

• Water, both in liquid and ice form, is a major contributor to erosion. The force of rain or moving bodies of water can cause rocks to loosen and break off, changing the earth's landscape. Rivers can create waterfalls, valleys or flood plains through erosion. When it rains in colder temperatures, the water gathers in rocks' crevices and cracks and eventually turns to ice. As it freezes, it expands, breaking apart the rocks. As the ice melts, it trickles down the rocks and carries fragments of the cracked rocks away. Additionally, acid rain causes the chemical erosion of rocks.

Wind

• Wind causes erosion through abrasion or deflation --- the removal of surface materials. Wind can force fragments of rocks or entire rocks to break off the surface of a mountain or slope.

Glaciers

• Mountain glaciers form when snow and ice begin to build up on the surface of rocks. The glaciers weigh heavily on the rocks, forcing them to move downhill. As the glacier slumps down the mountain, the rocks change the terrain by carving out a path. When the glacier melts, it transports the rocky debris to nearby bodies of water.

Plants and Animals

• Plants, such as mosses and lichens, take root in rocks' cracks and crevices. They expand these cracks as they grow, causing fragments of the rocks to fall off. Small and large critters crush and trample rocks as they scurry across them or burrow underground.

Human Activity

• Human activity, such as construction, deforestation or land mining can also cause rocks to break away from their surfaces. When construction workers, for instance, begin work on the project, they may change the surface of the land to ensure it is level for building on. Human activity is one of the more dangerous causes of erosion because it causes rocks to erode quickly. Today, many are working to minimize the impacts of construction or mining through the implementation of erosion and sediment-control measures to prevent soil and rock movement.