Permafrost characteristics and distribution Flashcards
What is the key environmental characteristic used to delimit current periglacial conditions?
The key environmental characteristic used to delimit current periglacial conditions is the presence of permafrost.
Define permafrost?
Permafrost is ground that remains at or below 0 degrees for at least two consecutive years. Permafrost may or may not contain ice and may be ‘unfrozen’, ‘partially frozen’ or ‘frozen’ depending on whether water or ice are actually present or not.
Permafrost is a thermal condition independent of what?
Permafrost is a thermal condition independent of its water/ice content.
Define the term cryotic?
The term cryotic refers to ground with a temperature below 0 degrees. The term refers solely to the temperature of the material.
Permafrost is more accurately known as what?
Permafrost is more accurately known as permanently cryotic ground that may or may not contain ice and may be ‘unfrozen’, ‘partially frozen’ or ‘frozen’ depending on the state of water or ice.
What is the study of permafrost known as?
The study of permafrost is called geocryology
What is the active layer?
The active layer is the zone of greatest temperature fluctuation within the upper layer of permafrost, which freezes and thaws seasonally. Its lower limit is the permafrost table, which causes the active layer to be poorly drained.
When does the active layer reach its maximum depth?
The active layer reaches its maximum depth at the end of summer, extending downward by up to 3 meters depending on the length and intensity of summer heating.
What is talik?
Talik is unfrozen ground within a permafrost environment.
Where is talik located?
In some places, localised unfrozen layers or taliks are located on top, underneath or within masses of permafrost.
What happens to permafrost thickness as latitude decreases?
Generally permafrost thickness decreases with decreasing latitude.
What are the three types of permafrost?
- Continuous permafrost
- Discontinuous permafrost
- Sporadic permafrost
Describe continuous permafrost?
Continuous permafrost forms in the coldest areas of the world where mean annual air temperatures are below -6 degrees. It can extend downwards for hundreds of meters.
Describe discontinuous permafrost?
Discontinuous permafrost is more fragmented and thinner.
Describe sporadic permafrost?
Sporadic permafrost occurs at the margins of periglacial environments and is usually very fragmented and only a few meters thick; it often occurs on shady hillsides or beneath peat.
