Permafrost

Similar term(s): pergelisol.

Definition:

A layer of soil or bedrock at a variable depth beneath the surface of the earth in which the temperature has been below freezing continuously from a few to several thousands of years.

More:

While the top layer of soil heats up in the summer, permafrost exists in deeper layers where the summer heating fails to melt the frozen ground. A continuous layer of permafrost is found in areas where the annual mean temperature is below about −5°C (23°F).

Source: based on AMS Glossary of Meteorology  

To read about this term in context:

GreenFacts Summary on Climate Change 2007 Update:

Translation(s):

Español: Permafrost
Français: Permafrost

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