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A glacier flows while its ice stays solid

Ice in a freezer feels brittle and rigid, yet a massive mountain glacier can flow slowly down a valley like a river of stone. Under the immense weight of thick ice, individual ice crystals deform and slide past one another internally, while meltwater at the base can lubricate the glacier and let the whole mass slip over the bedrock below.

3–5 min

Questions you could explore

  • What changes inside ice when it deforms?
  • When can a glacier move over its bed?

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4–5 min

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A glacier flows while its ice stays solid | Speech Topic | speaking.app