Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water. A similar process, weathering, breaks down or dissolves rock, but does not involve movement. Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier).

THE FORCES OF EROSION: WATER, GLACIERS, AND WIND But the most powerful erosive force on earth is not wind but water, which causes erosion in its solid form — ice-and as a liquid. Water in its liquid form causes erosion in many ways.

Major factors that affect the amount of erosion are soil cloddiness, surface roughness, wind speed, soil moisture, field size, and vegetative cover. A discussion of each follows. The cloddiness of a given soil largely indicates whether the wind will erode it.

The two main types of erosion are:

• Abrasion – as the glacier moves downhill, rocks that have been frozen into the base and sides of the glacier scrape the rock beneath.
• Plucking – rocks become frozen into the bottom and sides of the glacier.

Glacier Landforms

• U-Shaped Valleys, Fjords, and Hanging Valleys. Glaciers carve a set of distinctive, steep-walled, flat-bottomed valleys.
• Cirques.
• Nunataks, Arêtes, and Horns.
• Lateral and Medial Moraines.
• Terminal and Recessional Moraines.
• Glacial Till and Glacial Flour.
• Glacial Erratics.
• Glacial Striations.

Glaciers erode the underlying rock by abrasion and plucking. Glacial meltwater seeps into cracks of the underlying rock, the water freezes and pushes pieces of rock outward. The rock is then plucked out and carried away by the flowing ice of the moving glacier (Figure below).

Glaciers can shape landscapes through erosion, or the removal of rock and sediment. They can erode bedrock by two different processes: Abrasion: The ice at the bottom of a glacier is not clean but usually has bits of rock, sediment, and debris. It is rough, like sandpaper.