Periglacial processes - Active layer processes

Question 1

Give three active layer periglacial processes?

Answer 1

• Cryoturbation
• Frost cracking
• Frost-heave

Question 2

Describe the process of cryoturbation?

Answer 2

Repeated freezing and thawing within the active layer causes expansion and contraction of the surrounding material beneath the ground. Horizontal beds of sediment are folded into formations called involutions.

Question 3

Give one feature associated with cryoturbation?

Answer 3

Involutions

Question 4

Describe the process of frost cracking?

Answer 4

Once the active layer freezes in the autumn, further sub-zero temperature decline causes the ground to contract and crack. These features extend from the surface through the active layer into the permafrost.

Question 5

Give some features associated with frost cracking?

Answer 5

• Ice wedges
• Ice-wedge polygons

Question 6

Describe the process of frost-heave?

Answer 6

When the active layer starts to refreeze in the autumn, ice crystals develop. This increases the volume of soil and causes the soil surface to expand upwards, pushing stones to the surface. The process is most significant in soil composed of fine grains.

Question 7

Give one feature associated with frost-heave?

Answer 7

Patterned ground