The influence of climate change in forming landforms

Question 1

Formation of patterned ground

Answer 1

Patterned ground is the collective term for a number of fairly small-scale features of periglacial environments
- as a result of frost-heave, large stones eventually reach the surface and that the ground is domed; the stones then move radially, typically 1-2 metres in diameter
- a particularly distinctive example of patterned ground can be seen in Barrow, Alaska

On the slope angles of 3-50 degrees, the larger stones move greater distance downslope and the polygons become elongated into stone garlands
- on slopes over 60 degrees, polygons lose their shape and stone stripes develop

Question 2

Formation of pingos

Answer 2

Pingos are round ice-cored hills that can be as much as 90 metres in height and 800 metres in diameter - they are essentially formed by ground ice which develops during the winter months as temperatures fall

Open system pingos form in valley bottoms where water from the surrounding slopes collect under gravity, freezes then expands under artesian pressure

Closed system pingos are those which develop beneath lake beds where the supply of water is from the immediate local area
- as permafrost grows during cold periods, groundwater beneath a lake is trapped by the permafrost below and the frozen lake above
- the saturated talik, or unfrozen ground, is compressed by the expanding ice around it and is under hydrostatic pressure
- when the talik eventually freezes it forces up the overlying sediments

Question 3

Formation of an ognip

Answer 3

Pingos collapse when temperatures rise and the ice core thaws, and when this happens the top of the dome collapses, leaving a rampart surrounding a circular depression, called an ognip