Why do glaciers carve U-shaped valleys?
Quick Answer
Glaciers carve U-shaped valleys because thick ice erodes both the floor and sides of a valley as it moves. This creates a wide, flat-bottomed valley with steep walls.
The Full Story
River valleys are usually V-shaped, but a glacier fills the valley and widens it by abrasion and plucking. Rocks frozen into the ice scrape the bedrock like sandpaper, while chunks of rock can be ripped away from the valley walls. Because the glacier is thick, erosion happens across a broad cross-section, not just at the center. When the ice retreats, it leaves behind a much broader U-shaped valley. The fjords of Norway and the Yosemite Valley are classic examples of glacial carving.
Key Facts
YouTube Angle
Suggested video title for this topic:
"Why do glaciers leave valleys that look scooped out by a giant spoon?"