Glacial Landforms UPSC: Erosional and depositional

Glacial erosion occurs through two primary mechanisms: plucking and abrasion. Plucking involves the glacier freezing onto bedrock, tearing out rock fragments as it moves. Abrasion refers to the grinding action of ice-entrained debris against the underlying surface, akin to sandpaper. These processes collectively sculpt the landscape into unique erosional features.

Cirques, also known as corries or cwms, are amphitheater-shaped hollows formed at the head of a glacier. They originate from the accumulation of snow in sheltered mountain hollows, which gradually transform into glacial ice. As the glacier grows, rotational movement within the ice deepens the basin, while freeze-thaw weathering at the headwall steepens the back and sides. A tarn lake often occupies the floor post-glaciation. Notable examples include the Cirque de Gavarnie in the Pyrenees and the Nanda Devi Cirque in the Indian Himalayas.

Adjacent cirques eroding a mountain from opposite sides create sharp, knife-edged ridges called arêtes. The Matterhorn in the Swiss Alps exemplifies a pyramidal peak or horn, formed when three or more cirques converge. In India, the Trishul Peak in Uttarakhand showcases similar characteristics.