The last expansion of the polar ice sheets took place about 18,000 years ago.

最后一次扩大发生在一万八千年前。

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Warmer temperatures cause water to expand,a phenomenon called thermal expansion, and cause glaciers and polar ice caps to melt.

VOA: standard.2009.11.09

The agency said worse case scenarios, including the contribution of polar ice melt and thermal expansion, could result in much higher levels occurring but these were now thought to be unlikely.

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