Erosional landforms

When glaciers slog down a mountain, they do some serious damage to it. Here is a introductory list to the forms of erosion caused by glaciers.

After passing, glaciers turn V-shaped valleys into U-shaped valleys ("glaciated valleys") with a wide, flat floor and steep sides. Fjords are one example of glacier valleys. Other examples can be found in most mountain ranges the world over. When a smaller glacier meets a larger one, the larger one will erode its valley's bottom more than will the smaller one, leaving the smaller one as a hanging valley, with a sharp drop from its outlet to the floor of the larger valley (which can make for some spectacular waterfalls, after the glaciers are gone).

A Cirque, also known as a corrie or a cwm, is a steep-walled semicircular basin formed by a small 'pocket glacier', which often feeds into a larger glacier. Aretes are narrow, jagged ridges formed when two cirques abut each other, eroding a ridge from two sides. A horn is a sharp point formed by three or more cirques eroding around a mountain peak, giving it very steep, sharp cliffs. The Matterhorn in Switzerland is an example of a horn. A tarn lake is refers to water that has collected in a cirque.

The continental ice sheets of ancient ice ages also scooped out large shallow basins in the land, which have often filled and become lakes. Many of the lakes on the Canadian Shield, including the ever popular Great Lakes, were created this way.

Roches moutonnées form when plucking and abrasion work together (see glacial erosion); the glacier drives up a hill, polishing the slope smooth, and then it does some serious plucking on the downslope. The result is a smooth, low up-slope, and a sharp, bumpy down-slope. Roches moutonnée translates as 'fleecy rocks' in French, on the theory that they look like a field of fluffy sheep from a distance. They are also sometimes called sheepbacks in English.

Depositional landforms

Glaciers are really big, and last for a really long time; therefore, even things that seem minor, like rocks falling down from the valley walls and silt deposits from streams, have plenty of chance to build themselves up into noteworthy formations. Here's a brief survey of some of the litter glaciers leave behind them.

As glaciers flow they pick up till, which is deposited in mounds called moraines. The largest of these are the terminal moraines, where the base of the glacier melts, dropping all of its collected till; Long Island is a famous example of a terminal moraine. Other types of moraine are the lateral moraines, where till collects at the edge of the valley, usually due to rocks from the valley walls falling onto the glacier, and medial moraines, where two glaciers meet, compacting their medial moraines betwixt them. Ground moraines are not hills per se, but the comparatively level deposits of till left by a quickly melting glacier.

The end moraine and the outwash plain may be studded with kettles, where large chunks of ice were deposited in with the till, and then melted, leaving large holes. The outwash plain will probably also have erratic boulders, boulders that have been washed far from their original homes are left surprised and naked in the middle of a field or swamp.

An esker is a winding ridge of deposited sand, gravel, and silt which is formed by streams of meltwater running underneath the glacier. These streams don't just run under the glaciers, but also over, beside, and through. Sometimes a pocket in the ice will collect silt and till; when the glacier melts, these are left as irregular, steep-sided mounds called kames. When these deposits fall in a stream running between the valley wall and the glacier, they may remain standing after the glacier melts, forming terraces; these are called kame terraces.

Drumlins are elongated oval mounds, placed like speed bumps across the path where a glacier had once passed over; we do not know what processes formed these.

This is not by any means a complete listing of glacier related landforms. I think I've covered the high points, but gosh darn it, there's hundreds of odd little geologics formed from glaciers, ice sheets, silt and till, and other glacier related processes. Ice is just plain cool.

Log in or registerto write something here or to contact authors.