Permafrost

Permafrost is soil or underwater sediment which continuously remains below 0 °C (32 °F) for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below a meter, the deepest is greater than 1,500 m (4,900 ft). Similarly, the area of individual permafrost zones may be limited to narrow mountain summits or extend across vast Arctic regions.

The ground beneath glaciers and ice sheets is not usually defined as permafrost, so on land, permafrost is generally located beneath a so-called active layer of soil which freezes and thaws depending on the season.

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Source: Wikipedia · Image: Wikimedia Commons · Public domain

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Every species, image, fact, and figure is drawn from Wikipedia and Wikimedia Commons, used under public-domain and Creative Commons licenses. No content is AI-generated.