Glaciers carve U-shaped valleys from steeper river-cut gorges
Rivers saw narrow V-shaped canyons; thick glacier ice, loaded with rock grit, grinds and plucks bedrock into broad U-shaped troughs with steep walls and flat floors.
Over ice ages the same ice streams deepen tributary junctions, leave hanging side valleys, and dump ridges of till. When the ice retreats, the carved shape remains as a signature of frozen rivers that once filled the mountains.
Landforms keep a memory. U-shaped valleys prove glaciers are not only frozen water — they are slow excavators that rewrite mountain hydrology for millennia.
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