Periglacial Landscapes

Question 1

Define permafrost

Answer 1

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

Found at high altitudes and latitudes

Question 2

What is the active layer

Answer 2

Thin layer of soil above the permafrost

Question 3

Permafrost can reach….km deep

Answer 3

1.5

Question 4

Give a typical feature of a periglacial area

Answer 4

Ice wedge polygons

Question 5

Permafrost covers…% exposed land surface in the Northern Hemisphere

Answer 5

25

Question 6

What is talik

Answer 6

Unfrozen ground within a periglacial area

Question 7

What is continuous permafrost

Answer 7

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

Arctic circle

Question 8

What is discontinuous permafrost

Answer 8

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

Question 9

What is sporadic permafrost

Answer 9

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

Question 10

Define periglacial areas

Answer 10

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

Not covered by snow and ice all year round

Question 11

Why do permafrost regions contain seasonal wetlands

Answer 11

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

Question 12

Why does the temperature of the permafrost increase with depth

Answer 12

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

Question 13

Distinguish the terms periglacial and permafrost

Answer 13

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

Question 14

What is frost-heave

Answer 14

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

Question 15

What is frost creep

Answer 15

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

Question 16

What is ground ice

Answer 16

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

Question 17

What is solifluction

Answer 17

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.

Question 18

What are ice wedges and how are they formed

Answer 18

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).

Question 19

What are pingos and how are they formed

Answer 19

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

Question 20

What are blockfields and felsenmeers and how are they formed

Answer 20

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

Question 21

What are solifluction lobes

Answer 21

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.