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