Soil, silt and rock located in perpetually cold areas, and that remains frozen year-round for two or more years.; A thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.
References
- UN Environment (2019). Global Environment Outlook – GEO-6 : Healthy Planet, Healthy People. Nairobi. DOI 10.1017/9781108627146.
GEO-1-6
Soil, silt and rock located in perpetually cold areas, and that remains frozen year-round for two or more years.; A thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.