frozen ground or permafrost

thaw basin

a depression of the permafrost table created by naturally induced thawing.

suscitic cryogenic fabric

a distinct soil micromorphology, resulting from the effects of freezing and thawing processes, in which coarser soil particles have vertical or near-vertical orientation.

surface thawing index

the cumulative number of degree-days above 0°C for the surface temperature (of the ground, pavement, etc.) during a given period.


A type of Pleistocene-age (formed 1.8 million to 10,000 years before present) permafrost that contains a significant amount of organic material with ice content of 50– to 90 percent by volume. Thawing yedoma is a significant source of atmospheric methane.

A yedoma in Russia shows the thick layer of ice and carbon material exposed along this body of water. --Credit: Vladimir Romanovsky

zone of gas-hydrate stability

that portion of the subsurface where the conditions of temperature and pressure are suitable for the formation and preservation of gas hydrates.

zero curtain

the persistence of a nearly constant temperature, very close to the freezing point, during annual freezing (and occasionally during thawing) of the active layer.

Young's Modulus

the ratio of increase in stress acting on a test specimen, to the resulting increase in strain, under constant transverse stress.

well-bonded permafrost

ice-bearing permafrost in which all the soil particles are held together by ice.

wedge ice

ice occurring in an ice wedge.

waterbody encircling a palsa

a water-filled depression surrounding a palsa.


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