Periglacial landforms

Question 1

How are open-system pingos formed?

Answer 1

Groundwater freezing - explain.
Water comes from the outside.
Ice expansion causes the over-lying sediments to heave upwards - dome feature.
Height - 50m.
East Greenland type.

Question 2

How are closed-system pingos formed?

Answer 2

Groundwater freezing - explain.
Water is trapped/enclosed between the freezing surface and the permafrost.
Overlying-sediments are pushed into a dome.
Mackenzie type.
Northern Canada - 1,000 pingos.
Sometimes collapses - leaves a hollow filled with meltwater = ognip.

Question 3

How is patterned ground formed?

Answer 3

Frost heave.
Ice lens grows in the autumn - active layer repeatedly freezes and thaws daily - uneven layer.
Water migrates into the ice lens - capillary action.
Ice lens grows - pushes surface up.
Larger stones roll outwards - fine sediment in the middle.
1-5m - stone polygons - gentle slopes.
6+ degree slopes - stone stripes.
E.g. Arctic Tundra.

Question 4

How are ice wedges formed?

Answer 4

Ground contraction.
Winter - ground contractions - cracks created.
Summer - cracks open again - filled with meltwater.
Meltwater - sediment - fills cracks.
Repeated process over 100 years - widens and deepens.
1m wide, 2-3m deep.
Ice-wedge polygons on the surface.
E.g. North West territories, Canada.