Online Geography Resources

Base knowledge and understanding

Context

The aim of this lesson:

• To be able to explain permafrost, patterned ground, solifluction, thermokarst, pingos.

Alternative map projections

Permafrost

Permafrost is defined on the basis of temperature, as soil or rock that remains below 0°C throughout the year, and forms when the ground cools sufficiently in winter to produce a frozen layer that persists throughout the following summer.

The atmospheric climate is the main factor determining the existence of permafrost. However, the spatial distribution, thickness and temperature of permafrost is highly dependent on the temperature at the ground surface. The temperature at the ground surface, although strongly related to climate, is influenced by several other environmental factors such as vegetation type and density, snow cover, drainage, and soil type. [Source]

Thermokarst

Thermokarst is a land surface characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws, that occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Alps. There are many kinds of thermokarst, including collapsed pingos, linear and polygonal troughs (patterned ground). Most thermokarst features relate to minor environmental changes which promote thawing.

Pingos

Patterned Ground

Solifluction

Review

Explain what permafrost is and where it is found. [6 marks]

Explain a reason for the formation of patterned ground in periglacial environments. [6 marks]

Explain the periglacial process of solifluction. [6 marks]

Explain the appearance of thermokarst environments. [6 marks]

Explain the periglacial landform pingos. [6 marks]