Glaciers carve a set of distinctive, steep-walled, flat-bottomed valleys. U-shaped valleys, fjords, and hanging valleys are examples of the kinds of valleys glaciers can erode.
Valley glaciers carve U-shaped valleys, as opposed to the V-shaped valleys carved by rivers. During periods when Earth’s climate cools, glaciers form and begin to flow downslope. Often, they take the easiest path, occupying the low V-shaped valleys once carved by rivers. As glaciers flow through these valleys, they concentrate erosive action over the entire valley, widening its floor and over-steepening its walls. After the glacier retreats, it leaves behind a flat-bottomed, steep-walled U-shaped valley.
Valley glaciers sometimes flow through narrow inlets (fjords) into the ocean. They over-steepen the walls around them, as they do when carving u-shaped valleys. Thus, fjords have tall, steep walls like glacial valleys, but their floors are below sea level and thus are inundated with ocean water.
A small mountain glacier may join a larger valley glacier, just as a stream may join a larger river. The smaller glacier, however, may not be as deep as the main one, and its base may be higher in elevation than the main glacier's base. When the glaciers retreat from the area where they formerly met, the floor of the u-shaped valley formed by the smaller glacier may be many feet above the main valley. Waterfalls often form at this point when rivers begin flow through the glacier valleys.
To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.
Last updated: February 9, 2018