Landforms developed out of external forces

Erosion is the physical removal and transport of material by mobile agents such as water, wind or ice.

The three common agents of erosion are:

  1. Water
  2. Wind
  3. Ice

These agents are mobile at the Earth’s surface and are responsible for the transport of sediment.

Erosion and mass wasting appear to be similar processes but have distinctly different causes. The movement of sediment by erosion requires mobile agents such a water, wind and ice. That is, the sediment is transported by the movement of the agents. Mass wasting (commonly referred to as landslides) involves the transfer of rock and soil downslope under the influence of gravity. Gravity is the key factor in mass wasting and the movement of material does not require a mobile agent.

Erosion (transport of sediment) usually ends with the deposition of sediments (and soil). Deposition occurs when the forces responsible for erosion are no longer sufficient to transport the sediment.

There are a wide variety of landscapes on the Earth’s surface where the deposition of sediments occur as the result of fluvial (rivers), aeolian (wind) and glacial (ice) erosion.