Permafrost

This article is about frozen ground. For other meanings, see Permafrost (disambiguation).

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In geology, permafrost or permafrost soil is soil that stays in a frozen state for more than two years in a row.

Related Topics:
Geology - Soil - Frozen

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The extent of permafrost can vary as the climate changes. Today, approximately 20% of the Earth's land mass is covered by permafrost (including discontinuous permafrost) or glacial ice. Seasonal frost commonly overlays permafrost and is called the active layer as it will thaw during the summer. Plant life can be supported only within the active layer because growth can occur only in soil that is fully thawed for some part of the year. Thickness of the active layer varies by year and location but is typically 0.6 - 4 m (2 to 12 feet) thick. The depth of the permafrost can in areas of continuous permafrost and harsh winters be very great (440m (1330 feet) at Barrow, Alaska and as much as 1493m (4510 feet) in the northern Lena and Yana River basins).

Related Topics:
Climate change - Earth - Glacial ice - Active layer - Plant - M - Feet - Barrow, Alaska - Lena - Yana River

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