active layer processes

Question 1

Frost heave

Answer 1

• active layer starts to refreeze
• ice crystals begin to develop
  increasing the volume of the soil and causes an upward expansion of the soil surface (domed shape)
• most significant in fine-grained materials

Question 2

sorting

Answer 2

• active frost shattering (freeze thaw)
• areas = vert stoney
• repeated freezing and thawing = stoney solids raise, sort snd arrange into patterns
• fines (sand, silt and clays) tend to migrate downwards
• upward migration explained via frost pull / push

Question 3

Frost pull

Answer 3

Stones adheres to ice within a freezing active layer and is drawn upwards as the ground heaves

Question 4

Frost push

Answer 4

• Stones have a lower specific heat capacity
• heat up and cool down faster than surrounding soil
• Descending freezing front moves through a stone quicker than through soil on either side of stone.
• soil immediately beneath a stone is likely to freeze and expand, pushing stones up.

Question 5

Cryoturbation structures

Answer 5

• Repeated freezing and thawing of near-surface deposits may result in involutions
• (involutions = dips and hills)

Question 6

Nivation

Answer 6

• Effects of snow on the landscape
• These include abrasion and free-thaw
• Melted now triggers mass movements such as a solifluction and slope wash
• These processes may produce the shallow pits known as nivation hollows
• These hollows may trap more snow and deepen further = more novations so that cirques or thermo-cirques are formed

Question 7

Ice wedges

Answer 7

Intense cooling and contraction of the permafrost in winter may cause polygonal patterns of cracks