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USGS CMG InfoBank: Erosive Power of Glaciers

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Comment: 10:05 - 10:56 (00:51)
Source: Annenberg/CPB Resources - Earth Revealed 23. Glaciers
Keywords: glacier, erosion, "glacial ice", "glacial polish", "glacial flow", bedrock, "glacial melt", grit, striation, valley, "valley profile", stream

Our transcription: The tremendous erosive power of moving ice is evident in areas where glaciers have melted away exposing the bedrock.
These surfaces were polished smooth by glacial ice.
Grit caught beneath the glacier carved long scratch marks, called "striations," in the polished rock as the ice flowed across it.
On a more impressive scale, the valleys once occupied by glaciers are carved out, acquiring steep walls and broad gently sloping floors.
This "U-shaped" valley profile contrasts greatly with the "V-shaped" profiles typical of un-glaciated stream valleys.

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