Periglacial Landscapes Flashcards Preview

A level Geography - Physical > Periglacial Landscapes > Flashcards

Flashcards in Periglacial Landscapes Deck (21)
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1
Q

Define permafrost

A

Frozen ground which remains frozen all year round for at least two consecutive years.

Found at high altitudes and latitudes

2
Q

What is the active layer

A

Thin layer of soil above the permafrost

3
Q

Permafrost can reach….km deep

A

1.5

4
Q

Give a typical feature of a periglacial area

A

Ice wedge polygons

5
Q

Permafrost covers…% exposed land surface in the Northern Hemisphere

A

25

6
Q

What is talik

A

Unfrozen ground within a periglacial area

7
Q

What is continuous permafrost

A

No gaps - found where the mean annual temperature is colder than - 5ºC

Arctic circle

8
Q

What is discontinuous permafrost

A

Widespread and some gaps - mean annual temperature is -1ºC to -5ºC

9
Q

What is sporadic permafrost

A

Isolated + small areas - mean annual temperatures are just below zero

10
Q

Define periglacial areas

A

used to be places at or near ice sheets/glaciers. Now associated with permafrost

Not covered by snow and ice all year round

11
Q

Why do permafrost regions contain seasonal wetlands

A

The active layer in the summer becomes boggy marshes - permafrost prevents melted water draining downwards

12
Q

Why does the temperature of the permafrost increase with depth

A

Lower altitudes, increased distance from the cold air, closer to the heat at the centre of the Earth

13
Q

Distinguish the terms periglacial and permafrost

A

Periglacial = associated with areas of permafrost but also includes areas of unfrozen ground, whereas permafrost is only areas of frozen ground

14
Q

What is frost-heave

A

Small-scale upwards displacement of soil particles as a result of the freezing and expansion of water in the active layer, just below the ground surface

15
Q

What is frost creep

A

When soil particles on a slope show a dominant movement downhill under gravity. Particles are raised perpendicular to the ground surface by frost heave and are dropped down further vertically due to gravity on thawing

Repeated cycles can cause particles to ‘creep’ downslope

16
Q

What is ground ice

A

develops when a supply of water exists and freezes to form a core of ice which can force sediment upwards towards the surface

17
Q

What is solifluction

A

The downslope movement of rock and soil particles due to gravity, including processes such as soil creep, mudflows and landslides.

Gelifuction refers specifically to soil flows in periglacial regions which occur when the active layer thaws and moves downslope under gravity, over the permafrost.

18
Q

What are ice wedges and how are they formed

A

Narrow surface ridges of irregular pentagons

Extremely low temperatures - cracks develop.
Meltwater falls into these cracks in the summer and freezes in the winter (expanding to form ice wedges).

19
Q

What are pingos and how are they formed

A

Mounds of earth-covered ice up to 70m high
Form on a site of a lake that has generally been filled with soil

In the summer, the ice core melts and the centre may collapse

20
Q

What are blockfields and felsenmeers and how are they formed

A

Extensive frost shattering bedrock consisting of broken u angular fragment of rock

Subjected to repeated cycles of freezing and thawing. More likely to occur in moderate rather than extreme conditions

21
Q

What are solifluction lobes

A

Small scale, tongue-like platforms that slip slowly downhill

The downslope movement of soil and rock in response to gravity in a periglacial environment - significant summer melting areas.