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Permafrost is frozen ground (soil/rock/sediment) that stays below 0 °C for at least two consecutive years; practically, it corresponds to mean annual temperatures of 0 °C or below.
Permafrost is defined as soil, rock, or sediment that remains frozen for more than two consecutive years. In practice, it occurs where the mean annual temperature is at or below 0 °C (32 °F). Permafrost typically lies beneath an “active layer” that freezes and thaws seasonally, and the boundary between the active layer and permafrost is sometimes called the permafrost table. Temperature criteria also determine how continuous permafrost is across a region. Permafrost formation is favored when mean annual air temperatures are below freezing, though local factors (such as snow insulation in some boreal forests) can create exceptions. If mean annual soil surface temperatures are only slightly below 0 °C, permafrost may form only in sheltered spots, producing discontinuous permafrost; colder mean annual soil temperatures support continuous permafrost. In addition, permafrost depth is limited by geothermal heat: it extends downward until geothermal warming and the mean annual surface temperature reach an equilibrium at 0 °C, defining the base depth of permafrost.
Permafrost is frozen ground (soil/rock/sediment) that stays below 0 °C for at least two consecutive years; practically, it corresponds to mean annual temperatures of 0 °C or below.
Permafrost usually underlies a seasonally thawing active layer; the active-layer/permafrost boundary is the permafrost table.
Continuity (sporadic, discontinuous, continuous) depends strongly on mean annual soil surface temperature, with warmer conditions producing patchier permafrost.
Permafrost depth is constrained by geothermal heat; the base depth occurs where the equilibrium temperature at depth reaches 0 °C.
Soil, rock, or sediment that continuously remains below 0 °C for two years or more.
The top layer of ground that freezes and thaws seasonally above the permafrost.
The boundary between the active layer and the permafrost itself.
The depth where geothermal heat and the mean annual surface temperature reach equilibrium at 0 °C.
Categories of permafrost coverage determined by mean annual soil surface temperature, where colder conditions support more widespread (continuous) permafrost.
“Can you explain what "Permafrost is frozen ground (soil/rock/sediment) that stays below 0 °C for at least two consecutive years; practically, it corresponds to mean annual temperatures of 0 °C or below." means in simple terms?”