3b. Peri-glacial landforms as a result of climate change Flashcards
1
Q
What does periglacial mean?
A
Near to or on the edge of a glacier
2
Q
What characteristics define a periglacial area?
A
- permafrost / active layer
- seasonal variations (above 0 in summer)
- freeze thaw cycles & frost heave
3
Q
Where are periglacial environments found?
A
- high latitude areas
- continental interiors
- high mountains (even at lower latitudes)
4
Q
What % of the Earth’s surface is covered by periglacial conditions?
A
25% (estimated that it was previously 50%)
5
Q
processes: frost heave
A
- stones heat up & cool down faster due to lower specific heat capacity
- as temp falls, water beneath stones freezes, expands pushing stones upwards towards surface
- ground ice also pushes material upwards creating a domes surface
6
Q
processes: freeze-thaw weathering
A
- happens due to seasonal fluctuations in temperature around freezing
(truly glacial climates like Antarctica stay below freezing all year)
7
Q
Periglacial landforms: patterned ground - sorted stone circles/polygons
A
- formed by frost heave:
- freeze-thaw in active layer above permafrost
- stone/larger particles have lower SHC so heat and cool faster
- temp drops –> surrounding material freezes –> expands –> pushes up large particles until exposed on surface –> roll down hill by gravity
8
Q
Periglacial landforms: patterned ground - stone stripes
A
- when stone circles form on a slope, the circles slowly move downslope, stretching into lines
9
Q
Periglacial landforms: open system pingo
A
- form in valley bottoms
- water collects in a valley bottom within an area of talik (unfrozen ground)
- when temp falls, water freezes & expands under artesian pressure
- surface material is forced to dome upwards
10
Q
Periglacial landforms: closed system pingo
A
- form beneath lake beds
- water from the lake seeps into talik beneath
- when temp falls, groundwater in talik is trapped by permafrost and frozen lake
- talik is compressed by expanding ice - under hydrostatic pressure
- eventually talik becomes frozen, expands, pushes up surface into a dome
11
Q
What impact will climate change have on patterned ground?
A
- rise in temperature has meant patterned ground is becoming more colonised and harder to identify
12
Q
What impact will climate change have on pingos?
A
- causes them to collapse
- when temperatures rise and the ice core thaws
- leaves a circular depression called an ognip
