Periglacial Processes & Associated Forms

Inactive Layer Permafrost

Inactive layer refers to the soil below which is frozen year-round because the heat fails to penetrate

Alpine

Permafrost in mountains

Subsea

Permafrost in oceans

Active Layer Permafrost

Top layer, called "active" because it is the part that thaws every summer and freezes every winter. Sometimes the layer can be very thick or not thick at all (about 5 meters to some cm).

Thaw Cycle

Warm weather melts ice and snow, filling pavement cracks with water. As temperatures drop, the water freezes and expands, breaking up the pavement.

Discontinuous Permafrost

DISCONTINUOUS Sporadic Isolated

Segregated Ice

Wedges Lenses

Patterned Ground

https://www.google.com/search?q=segregated+ice+wedges+and+lenses&biw=1280&bih=611&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBwQsARqFQoTCKikhJDAk8kCFQNEJgode_UAKQ#tbm=isch&q=periglacial+patterned+ground&imgrc=oJ_auwvN0cChKM%3A

Pingo

A dome-shaped mound consisting of a layer of soil over a large core of ice, occurring in permafrost areas

Interstitial Cycle

AKA ground ice Ice forms between the pores of the ground = heaving Develops anywhere the ground freezes

Talik

An area of unfrozen ground surrounded by permafrost

Permafrost

Thick layers of soil or sediments and rocks that remains frozen for at least two consecutive years A thick subsurface layer of soil that remains frozen throughout the year, occurring chiefly in polar regions.

Continuous Permafrost

Where there is at least 90% of ice in the ground CONTINUOUS

Relict

Where we used to have a lot of permafrost at a given time but now there is just one random patch