What is permafrost?
Permafrost is ground that remains frozen for at least two consecutive years.
Formation, concepts and processes
The active layer above may thaw in summer and refreeze in winter. Frozen ground may contain ice, organic matter and minerals in varying proportions. Permafrost need not carry permanent snow and occurs beyond polar regions.
Examples, applications and limits
Warming can cause subsidence, infrastructure damage and altered drainage in ice-rich ground. Thawing organic matter may affect greenhouse gas emissions. Local ground temperature, snow cover and topography shape outcomes.
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