Comment: 05:25 - 06:38 (01:13)
Source: Annenberg/CPB Resources - Earth Revealed 23. Glaciers
Keywords: "Louis Agassi", "James Zumberge", glacier, "glacial flow", glaciologist, drilling, Swiss, friction, creep, bedrock, "basal slip", "glacial melt", snout
Our transcription: Scientists like Agassi also wanted to understand how glaciers flow internally.
But it wasn't until early in the post World War II era that glaciologists were able to drill a hole through a Swiss glacier.
This was a hole several hundred meters deep, maybe a couple of inches in diameter or smaller, but they put an aluminum tube in that hole right down to the bottom of the glacier.
The scientists discovered that the tube bent as it shifted down-slope.
So just as friction slows movement of ice at the sides of glaciers, it slows movement at the base as well.
Scientists also discovered that glaciers not only creep over the bedrock, but in places break free to glide across it.
Such basal slip is lubricated by water melting from the ice.
Streams of this sub-glacial melt water commonly pour from the snouts of glaciers.
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