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What is permafrost? What are the forming conditions of permafrost?
发布时间: 2020-09-04 11:20

  With the aggravation of global warming, people pay more and more attention to permafrost. Once the permafrost melts in large quantities, the threat to human beings cannot be ignored. So what is permafrost? How was it formed and what conditions were there?

  Definition of permafrost**

  The scientific name of permafrost is permafrost, also known as permafrost. It is essentially a soil rock layer, but it is frozen for many years. The distribution of Permafrost on the earth is gradually thinning from high latitude to low latitude. In the Arctic, the thickness of permafrost reaches more than 1000 meters, while near 48 degrees north latitude, the thickness of permafrost decreases to 1 to 2 meters, which is also the southern boundary of permafrost.

  The permafrost is usually divided into two layers, the upper layer will cycle between melting and freezing with seasonal changes, while the lower layer is in a long-term or even permanent ice state under the existing climate conditions of the earth.

  In most cases, the water content in permafrost even exceeds the potential water saturation of surface materials. However, in some cases, the permafrost does not necessarily contain water. For example, in some places, the main rock type in the permafrost is the non porous bedrock.

  Formation conditions of permafrost**

  First of all, the local annual average temperature must be lower than zero. Otherwise, it can only form seasonal frozen soil instead of permafrost;

  There must be long-term accumulation. It is found that the thickness of permafrost in the Arctic usually reaches several hundred meters or more, and the atmospheric low temperature can not be transmitted so deep. Therefore, the formation time of the Arctic permafrost has experienced at least several hundred years or even longer;

  In general, a large number of permafrost are concentrated in high latitude, the only exception is the permafrost zone of the Qinghai Tibet Plateau. High latitude and high altitude are important conditions for the formation of permafrost.

   (source: soil flow network)