What Is Erosion and How Does It Shape the Earth's Surface?

Erosion Is a Central Concept in Geology

Providence Canyon, Georgia.
Providence Canyon State Park, Georgia. Providence Canyon was formed in the early 1800s from poor farming practices. Franz Marc Frei / Lonely Planet Images / Getty Images

Erosion is the name for the processes that both break down rocks (weathering) and carry away the breakdown products (transportation). As a general rule, if rock is just broken down through mechanical or chemical means, then weathering has occurred. If that broken-down material gets moved at all by water, wind or ice, then erosion has occurred. 

Erosion is different from mass wasting, which refers to the downslope movement of rocks, dirt, and regolith primarily through gravity.

Examples of mass wasting are landslides, rockfalls, slumps, and soil creep; visit the Landslides Photo Gallery for more information. 

Erosion, mass wasting, and weathering are classified as separate actions and often discussed individually. In reality, they are overlapping processes that usually act together. 

The physical processes of erosion are called corrasion or mechanical erosion, while the chemical processes are called corrosion or chemical erosion. Many examples of erosion include both corrasion and corrosion.

Agents of Erosion

The agents of erosion are ice, water, waves, and wind. As with any natural process that takes place on the Earth's surface, gravity plays a major role as well.

Water is perhaps the most important (or at least most visible) agent of erosion. Raindrops strike the surface of the Earth with enough force to break apart soil in a process known as splash erosion. Sheet erosion occurs as water collects on the surface and moves toward small streams and rivulets, removing a widespread, thin layer of soil along the way.

Gully and rill erosion occurs as runoff becomes concentrated enough to remove and transport larger amounts of soil. Streams, depending on their size and speed, can erode away banks and bedrock and transport large pieces of sediment. 

Glaciers erode through abrasion and plucking. Abrasion occurs as rocks and debris become embedded on the bottom and sides of a glacier.

As the glacier moves, the rocks scour and scratch the surface of the Earth.

Plucking takes place when meltwater enters cracks in the rock beneath a glacier. The water refreezes and breaks off large pieces of rock, which are then transported by glacial movement. U-shaped valleys and moraines are visible reminders of the awesome erosive (and depositional) power of glaciers. 

Waves cause erosion by cutting away at the shore. This process creates remarkable landforms like wave-cut platforms, sea arches, sea stacks, and chimneys. Due to the constant battering of wave energy, these landforms are usually short lived. 

Wind affects the surface of the Earth through deflation and abrasion. Deflation refers to the removal and transport of fine-grained sediment from the wind's turbulent flow. As the sediment is airborne, it may grind and wear away surfaces with which it comes in contact. Like with glacial erosion, this process is known as abrasion. Wind erosion is most common in flat, arid areas with loose, sandy soils. 

Human Impact on Erosion

Although erosion is a natural process, human activities like agriculture, construction, deforestation, and grazing can greatly increase its impact. Agriculture is particularly notorious.

Areas that are conventionally plowed experience upwards of 10 times more erosion than normal. Soil forms at about the same rate that it naturally erodes, meaning that humans are currently stripping away the soil at a very unsustainable rate. 

Providence Canyon, sometimes referred to as "Georgia's Little Grand Canyon," is a strong testament to the erosional effects of poor farming practices. The canyon began forming in the early 19th century as rainwater runoff from the fields caused gully erosion. Now, just 200 years later, guests can see 74 million years of beautifully layered sedimentary rock in the 150-foot canyon walls.