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Comment: 08:59 - 10:05 (01:06)
Source: Annenberg/CPB Resources - Earth Revealed 23. Glaciers
Keywords: "J. Lawford Anderson", "glacial advance", "glacial retreat", glacier, "glacial ice", "glacial melt", "glacial flow", rock, silt, "mechanical weathering", bedrock, erosion, "glacial polish", topography, stream, snout

Our transcription: Whether the snout of the glacier advances or retreats, ice within the glacier itself is continuously flowing down-slope to melt away.
As it does so, the ice carries tons of rock, silt, and other debris.
Some of this material comes from the mechanical weathering and toppling of rocks onto the surface of the glacier; other material is plucked and scraped out by the ice as it flows across the bedrock.
Well, glaciers erode in a very characteristic style.
They polish.
They grind.
They gouge.
They pluck away at the rocks that are there, totally destroying any topography that was already present.
Any streams in its path are obliterated by the oncoming ice.
The ice itself is hardly pure; it's dirty; it's filled with everything that the ice has previously scratched and ground away at.
So a glacier is moving like ice-filled sandpaper and uses the rocks and sand debris within itself to further gouge and scrape the earth.

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