Special Sub-Topic: Permafrost Click Here To Play: Permafrost

Permafrost or permanently frozen ground is traditionally defined as:

ground that remains at or below 0 degrees C for at least 2 years. Only two winters are required for ground to be considered permafrost making the word permanently frozen ground a bit of a misnomer but that is the recognized definition.

Permafrost covers what percentage of the earth's surface?

about 25 percent. The percentage fluctuates between 20 and 25 percent and adds up to about 150 million square kilometers.

Where has the deepest penetration of permafrost been measured to date?

Russia. Measurements in excess of 600 meters have been made in the northern Siberian region of Russia. Depths of 300-400 m exist in Alaska and Canada with shallower depths in Antarctica due to the insulating effect of the ice caps.

The distribution of permafrost is controlled by many variables but the most important is:

climate. Climate itself has so many variables that its effect on the ground thermal regime far outweighs all other factors.

Which feature develops as a result of permafrost degradation?

alas. Alas is the Russian term for a large depression formed when permafrost thaws and subsides. The other features are aggradational caused by the growth of ground ice.