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Periglacial landforms

You should be able to describe and explain the formation of various periglacial landforms including

• Tors• Blockfields• Pingos• Ice wedges• Patterned ground• Talus• Solifluction lobes

TORS, TALUS AND BLOCKFIELDS

Patterned ground

Ice Wedges

Talik

Permafrost Permafrost

Active Layer – unfrozen in summer

Atmosphere

Talik

Permafrost

PermafrostPermafrost

Atmosphere

Active layer freezes from surface down

This starts to freeze water in the Talik trapped between the freezing active layer and the permafrost, creating and ice lens

Permafrost

PermafrostTalik

Atmosphere

Ice Lens

Water rises to the ice lens due to hydraulic pressure

Crack appear where the surface ruptures

The formation of an open system pingo stage 1

The formation of an open system pingo stage 3The formation of an open system pingo

stage 2

Permafrost

Permafrost

Permafrost Advances during colder periods

Permafrost

Talik

Talik

A frozen lake with sediment on the floor insulates the ground beneath against the cold – this allows talik to exist

Lake sediment

Unfrozen water

Unfrozen waterUnfrozen waterIce forms from unfrozen water as permafrost advances , the ice lens increases in size due hydrostatic pressure

Lake sediment is pushed up into the dome shaped pingo

Closed system pingo formation stage 1

Closed system pingo formation stage 2

Periglacial landformsPatterned ground

Open system pingos

Closed system pingos

Solifluction sheets and lobes

Tors Ice wedge polygons

Nivation hollows

Talus (scree)

Blockfields

Key features (size, shape, appearance)

Processes involved

Explanation of how created

Located Example

http://www.arctic.uoguelph.ca/cpe/environments/land/land_frame.htm

Name the features on the diagram

Attempt question 5 and 7 on page 139 of WaughResearch question 8

Open system pingos

Large domes up to 50m high and 300m across. Circular in shape with a core of ice and surface of soil.

Freeze Thaw, Capillary actionFormation of Ice lenses

Open system pingos occur in valley bottoms where water moves to the base of the valley during the thaw season when the active layer has thawed. When temperature drops ice lenses can form in this location. Water migrates to these lenses by capillary action. On contact with the ice lenses the water freezes, swelling the size of the lense.Over time this will swell the size of the land surface to create round hills called pingos. When the pingo becomes too large cracks appear on the surface. This exposes the ice to the sun and melting occurs. The pingo collapses leaving a lake (ognip) surrounded by a ridge or rampart.

East Greenland

Describe and explain the formation of open and closed system Pingos

Locate your case studies of landforms on the map below