Glacial Landforms

Notes

Glaciers are large, slow-moving masses of ice. Types: continental ice sheets (Greenland, Antarctica), valley (Alpine) glaciers, piedmont glaciers and ice caps. Glaciers erode by plucking (quarrying) and abrasion.

Erosional landforms

Cirque: an armchair-shaped hollow at the head of a glacier; a tarn lake forms when ice melts.
Arete: a knife-edge ridge between two cirques.
Horn (pyramidal peak): where several cirques cut a peak (Matterhorn).
U-shaped valley (glacial trough); truncated spurs.
Hanging valley: a tributary glacier valley left high above the main valley, often with a waterfall.
Fjord: a deep, narrow sea inlet formed when a glaciated valley is drowned (Norway, Chile, New Zealand, Alaska).
Ribbon lakes (finger lakes), roches moutonnees, crag and tail.

Depositional landforms

Moraines: ground, lateral, medial, terminal (end) and recessional moraines.
Drumlins: oval hills of till that give a "basket of eggs" topography; the steep end faces the direction the ice came from.
Eskers: long, winding ridges deposited by sub-glacial streams.
Kames and kame terraces; outwash plains (sandur); erratics (boulders carried far from their source); kettle holes and lakes; varves.

Examples: the Great Lakes and the lakes of Finland are glacial in origin. In India: the Gangotri glacier (source of the Bhagirathi, from Gomukh), Siachen (Karakoram; about 76 km, among the longest non-polar glaciers), Zemu (Sikkim), Pindari, Milam.

Key Points

Erosional: cirque, arete, horn, U-valley, hanging valley, fjord.
Depositional: moraines, drumlins, eskers, kames, outwash plains, erratics.
Fjord = drowned glaciated valley.
Drumlin = "basket of eggs"; esker = winding ridge.
Gangotri and Siachen are major Indian glaciers.

MCQs

Q1. An armchair-shaped hollow at the head of a glacier is a:

(a) Cirque
(b) Arete
(c) Drumlin
(d) Esker
Ans:
(a).

Q2. Which landform gives a "basket of eggs" topography?

(a) Esker
(b) Kame
(c) Drumlin
(d) Moraine
Ans: (c).

Q3. A fjord is:

(a) A drowned river valley (ria)
(b) A drowned glaciated valley
(c) A coral lagoon
(d) A coastal sand bar
Ans: (b).