Periglacial landforms

Question 1

Periglacial landforms

Answer 1

• Patterned ground
• Ice wedges
• Pingos
• Blockfields
• Solifluction lobes
• Terracettes
• Thermokarst

Question 2

Patterned ground

Answer 2

• Stones on surface are arranged in circle, polygons, stripes
  = Frost heave or Frost contraction

Question 3

Frost heave

Answer 3

• Water underneath stones freezes and expands
  = Stone upwards
  = Reaching surface = roll down to edges of mounds
  = Form a circle

Question 4

Frost contraction

Answer 4

• Ground cracks in polygon shapes
• Gaps fill with stones
  = Polygon patterns on surface

Question 5

Ice wedges

Answer 5

FROST CONTRACTION
- Temps drop low in Winter
= Ground contracts and cracks form in permafrost
- Can re-open in same place
= Splitting ice wedge = more water seeps in + freezes
= Widening ice wedge

ICE WEDGES
- Spring - increase in temp
= Active layer thaws + meltwater seeps into cracks
- Ice-filled cracks formed

Question 6

Pingos

Answer 6

• Conical hill with a core of ice

Two types;

• Open system
• Closed system

Question 7

Open-system

Answer 7

• Discontinuous permafrost
• Groundwater forced up thru gaps between areas of permafrost
• Water collects + freezes = core of ice which expands
  = Push ground up

Question 8

Closed system

Answer 8

• Continuous permafrost = lake on surface
• Lake insulates ground = beneath remains frozen
• Lake dries up = no longer insulated
  = Permafrost advances around unfrozen ground
  = Water collects in centre of unfrozen ground
• Water freezes = core of ice that pushes ground upwards

Question 9

Blockfields

Answer 9

• Expanses of loose rocks
• Formed in place by frost shattering of bedrock layer
  = Repeated freezing + thawing

Question 10

Solifluction lobes

Answer 10

• Type of slope failure
  = Sediments form a tongue-shaped feature = differential downhill flow rates.
• Occur = saturated soils in high lats (within + beyond permafrost zone)
• Takes place under periglacial conditions = veg coverage is limited
• Winter = bedrock + soil are frozen
• Summer = active layer thaws - underlaying layer remains frozen
• Acts like impermeable rocks = surface meltwater can’t infiltrate down + temps aren’t high enough for effective evaporation.

Question 11

Terracettes

Answer 11

• Steps formed on a slope
  = Freezing + thawing of ground = particles move downhill
• Active layer affected by frost heave in Spring + Autumn
• Frost heave = soil move perpendicular towards surface due to expansion = freezing
• Thawing = particles move gradually downhill with every cycle of freezing + thawing.

Question 12

Thermokarst

Answer 12

• Landscape with irregular marshy or lake filled hollows
  = occurs when ice in ground melts = ground collapses
• Holes fill with water = uneven, marshy landscape