Britannica Sources used in this answer

How do glaciers shape mountain landscapes?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A car drives along the Trans-Canada Highway with Mount Sir Donald's sharp, snow-capped peak rising above forested slopes in the Selkirk Mountains, British Columbia. — mountain Mount Sir Donald in the Selkirk Mountains, British Columbia, looms above a segment of the Trans-Canada Highway.

Glaciers profoundly reshape mountain landscapes through intense erosional processes that transform V-shaped stream valleys into broad, parabolic U-shaped valleys. As glaciers move, they remove loose debris and aggressively erode the bedrock along the base and lower sidewalls of valleys, creating steep or even vertical cliffs.21

This glacial sculpting creates several distinct landforms:

Cirques and Tarns: Glaciers often originate in cirques, which are amphitheatre-shaped hollows carved into mountainsides. When these basins are over-deepened and later fill with water, they form lakes known as tarns.2
Arêtes and Horns: As cirques erode headward, they narrow the ridges between parallel valleys into sharp, knife-edge arêtes. When multiple cirques erode around a single peak, they leave behind a jagged, pyramid-shaped horn, such as the Matterhorn.23
Hanging Valleys: Because smaller tributary glaciers erode their troughs less rapidly than the main glacier, they are left as hanging valleys high above the main valley floor once the ice melts, often resulting in waterfalls.13

Through these processes, glaciers replace the rugged, V-shaped profiles of river-carved mountains with the dramatic, smoothed, and deepened topography characteristic of high alpine ranges.24