Question

Answer in detail:

Explain the landforms formed by different agents through the process of abrasion.

Answer 1

Abrasion involves the scratching and polishing of the surface of bedrock by the particles which are moving onto it. Let us study different landforms formed by different agents of erosion through the process of abrasion.

Work of Seas Waves:

1. Sea cliffs:
   Sea cliffs are carved where waves strike directly against rocks. The softer rock along the coastline gets eroded first.
2. Caves:
   Sometimes, waves can erode the softer part and make it hollow enough to be called a cave.
3. A sea arch:
   A sea arch forms when waves erode a layer of soft rock underneath a layer of hard rock.
4. Sea stack:
   If a sea arch collapses, it creates a sea stack, which looks like a large rock in the middle of the water.
5. Headland:
   The part of land projecting into the sea is called headland.
6. Wave-cut platforms:
   Surfaces at the base of the cliffs are called wave-cut platforms. Extensive platforms are developed where the rocks are least resistant to wave erosion. They are visible at lower water levels, such as at low tide.

Work of Wind:

1. Ventifacts:
   Abrasion carves the windward side of rock into a smooth sloping surface. These rocks are called ventifacts.
2. Mushroom rocks :
   The high rising rocks in the path of the wind are attacked by the sand that moves with the wind.
   Winds and the particles they carry attack the base of an individual rock.
   The larger top part is .not eroded as much as the basal part because the particles are not lifted at a height.
   The particles at medium height are smaller but their velocities are high. Hence, their impact is more.
   As a result, the portion of rock at medium height is eroded more and the rock as a whole gets the shape of a mushroom.
3. Yardang:
   In areas where hard and soft rocks are found, the softer rocks get more eroded faster.
   The eroded portion of softer rocks appear like elongated ridges and harder rocks appear as elevated portions.
   A yardang is the remaining part of a ridge where rocks have been eroded.

Work of Glaciers:

1. Roche moutonnee :
   They are bedrock hills that are smoothly rounded on the upper side by abrasion and plucking on the lower side.
2. Cirque :
   An armchair like feature is formed when ice movement accompanied by weathering and mass wasting steepens the wall at the head of the glacier.
   It deepens into an armchair-shaped depression called a cirque.
3. Arete:
   Often two or more cirques develop side by side.
   This leaves the area between any two of them into a narrow wall. This is called arete.
4. Horn:
   When three or more cirques are formed, the headward erosion of the glacier erodes the summit.
   This leads to the formation of a characteristic peak which is called a horn. The Matterhorn in the Swiss Alps is an example.
5. U-Shaped Valleys:
   When glaciers move ahead, they erode the sides as well as the bottom of the valleys they flow through. This makes the valley broad at the bottom, forming a 'U'. This is called a U-shaped valley.