Glacial Features Geography 12

Cirque An arm-chair shaped depression. Often where alpine glaciers begin their formation. The depression is hollowed out as the glacial ice begins to erode through freeze-thaw and plucking.

Arête A thin, knife-like ridge usually formed with two glaciers erode parallel U-shaped valleys. The term comes from the French word for fishbone, because this is what they are sometimes described as looking like.

Pyramidal Peak AKA Glacial Horn. Formed when three or more cirques have modified a mountain side. Most famous: Matterhorn in Switzerland.

Hanging Valley Smaller glaciers may feed into the larger glacier forming smaller U-shaped valleys on the larger valley sides. When the glaciers melt, we are left with valleys that appear to be hanging on the sides of the large valley. Waterfalls are commonly associated with hanging valleys.

Roche Moutonée Rock formation created by the passing of a glacier. When the glacier erodes to the bedrock, tear- drop shaped hills can form. They taper in the up ice direction.

Crag and Tail Formed when the glacial moves over rock that is resistant to erosion. The glacier erodes the surrounding softer material. The Crag is the rock that is more resistant and servers to protect the less resistant rock behind it (the tail).

Drumlin An elongated whale-shaped hill made of unconsolidated till or ground moraine. Its long axis is parallel with glacial movement with the blunt edge facing up ice. Typically 1-2 km long and 300 - 600 m wide. Often found in drumlin fields.

Kettle Lake A shallow, sediment-filled body of water formed by retreating glaciers. Large blocks of ice break off the nose of a retreating glacier and a covered with sediment. They will eventually melt forming these lakes.

Tarn Mountain lake formed in a cirque.

Esker A long winding ridge of stratified gravel and sand. Believed to have been formed in ice walled tunnels and streams.

Moraine Any glacially formed accumulation of unconsolidated debris. Many different types named for where they form within the glacier.

Lateral Moraine Parallel ridges of material deposited along the sides of the glacier.

Ground Moraine Material deposited at the base of a glacier. Till may be modified into drumlins as the glacier moves over it.

Terminal Moraine AKA End moraine. Form at the end point that the glacier travelled to. Usually in the shape of the nose of the glacier. Lakes may form behind the terminal moraine as the glacier retreats.

Recessional Moraines Created as the glacier retreats. Formed parallel to the terminal moraine. Like ‘mini’ end moraines indicating times that the glacial movement stopped.

Medial Moraine Runs down the middle of a valley form. Forms when two glaciers meet and there lateral moraines are fused together.

Erratic Piece of rock that differs in size and composition from the native rock to the area in which is rests. Rock has been transported by a glacier and deposited somewhere else. Range in size from pebbles to large boulders.