August 27, 2004
This photo was taken in southcentral Montana along the Beartooth Scenic Highway. The valley shown in the photo is a “glacial trough” sculpted by an alpine glacier that flowed though here during the last ice age over 10,000 years ago. Valleys carved by rivers in mountainous areas tend to have distinct V-shapes, whereas those shaped by glaciers tend to be U-shaped. During the ice ages glaciers formed in some of Montana’s high mountainous areas near the upper portions of river basins and then flowed down through river valleys. Along the way the glaciers plucked rock material from the valley walls, widening and re-shaping them as they plowed through.