Erosion takes place usually through the following agents:
- Running Water
- Coastal Waves
- Chemical Solution
(1). Running Water:
Running water in the form of rivers and streams is a major source of erosion. Rivers and the streams act as sculptors, carvers, and cutters of the mountains, valleys, and plains through which they pass. The rivers disgorge billions of tons of the silt manually into the oceans whereas a part of the load is spread over the plains and deltas. Rivers are actually complex gradational systems depending on the slope (gradient) of the valley, the form of the valley, and the amount of water. Flowing water also plays a key role in shaping the landscape of deserts. On their way to the oceans, the rivers are joined by small rivers (tributaries). Thus the geomorphic history of the region can be studied through its stream system. The erosion by rivers takes place in the following ways:
- Hydraulic Action: The running water dislodged and drags away rock material from the valley floor and sides. It is called hydraulic action.
- Abrasion: The erosion action of boulders, pebbles, and grains of sediment along the river valley is called abrasion.
- Corrosion: It is the process by which rocks and minerals are dissolved by stream water. For example, limestone is eroded by hydraulic action, abrasion, and corrosion. Similarly, sandstones are weakened when their cement is dissolved.
(2). Glacial Movement:
Glaciers also perform erosional work to some extent as they gradually move down the slope of mountains. This activity can be classified as under:
- The glaciers carry out erosional work in the mountainous regions by plucking big pieces of rocks, grooving, scratching, and chiseling.
- The glaciers build new areas by depositing rock material.
- The large glaciers disturb the drainage system in the mountains and valleys.
(3). Winds Action:
The wind is a great agent of erosion due to the following actions:
Wind performs erosive work by lifting huge quantities of loose material on the Earth such as particles of sand and dust. It also polishes the surface of rocks.
- In the desert areas, the wind carries huge amounts of sand from one place to another forming dunes. thus it carries out depositional work.
(4). Coastal Waves:
The coastal waves also perform major erosive work alongside the coastal areas. Main destructional forms resulting from erosion include sprouting horns, chasms, stacks, and offshore benches. Similarly, the waves also carry out depositional work through which the development of shoreline and coastline takes place. The hydraulic action of waves has a direct shattering effect on the rocks. The material broken from the cliffs is transported by water to other places. It is called coastal deposition. Read: Depositional Landform