Permafrost
Permafrost
Permafrost (/ˈpɜːrməˌfrɒst/) is a permanently frozen layer of soil, sediment, or rock that remains at or below 0°C (32°F) for at least two years. It is a significant feature of the Earth's polar and alpine environments.
Etymology
The term "permafrost" is derived from the English words "permanent" and "frost", indicating its enduring and frozen nature. It was first used in 1943 by Siemon W. Muller, an American geologist, to describe the permanently frozen ground in Alaska.
Characteristics
Permafrost is characterized by its temperature, ice content, and thickness. It can extend from a few meters below the surface to more than 1,500 meters in the coldest regions. The upper layer of permafrost, known as the active layer, thaws during the summer and refreezes in the winter.
Distribution
Permafrost is found in high-latitude regions like the Arctic, Antarctica, and parts of the Himalayas. It also occurs in subsea continental shelves and alpine regions.
Related Terms
- Active layer: The top layer of ground subject to annual thawing and freezing in areas underlain by permafrost.
- Thermokarst: A land surface characterized by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws.
- Cryosphere: The frozen water part of the Earth system, which includes permafrost.
Impact
Permafrost plays a crucial role in the global climate system, as it stores large amounts of carbon. When permafrost thaws, it releases greenhouse gases, contributing to global warming.
See Also
External links
- Medical encyclopedia article on Permafrost
- Wikipedia's article - Permafrost
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