Ice-wedge polygons

Question 1

Where are ice-wedge polygons found?

Answer 1

Ice-wedge polygons are unique to periglacial areas and are usually found on valley floors.

Question 2

Describe the formation of ice-wedge polygons?

Answer 2

• During summer, when the active layer thaws, water flows down into the cracks which become filled with meltwater and debris
• In the subsequent winter, any water-filled cracks expand as ice forms. Over time, the cracks widen to form ice wedges.
• Repeated freezing and thawing leads to the formation of wedges through frost cracking that are 1 to 2 meters wide at the top and up to 8 to 10 meters deep; such features may take around 100 years to form.

Question 3

How do ice-wedge polygons differ from patterned ground?

Answer 3

Ice-wedge polygons differ from patterned ground in that they are larger, and their edges are slightly higher than their centres, whereas frost-heave polygons are domed.

Question 4

What happens to the active layer and what is the impact of this?

Answer 4

In the winter, the active layer freezes and the soil layer contracts and frost cracking forms natural polygonal patterns 5 to 30 meters across.