periglacial landforms

Question 1

what is periglaciation?

Answer 1

cold environments in which ice is the dominant force but no glaciers are present

Question 2

how are periglaciated areas defined more widely?

Answer 2

an area with:
-permafrost
-with some seasonal temp variation where the mean temp for at least some period in the summer rise above 0 degrees
-where freeze-thaw cycles dominate the landform creating processes

Question 3

what % of periglaciated areas make up the world?

Answer 3

25%

Question 4

what is permafrost?

Answer 4

the permanently frozen ground where soil temperatures have remained below 0 degrees for at least two years

Question 5

what is continuous permafrost?

Answer 5

summers are so cold that there is only a very superficial surface melting of the ground
it has established to reach up to a depth of 1500 m

Question 6

what is discontinuous permafrost?

Answer 6

found in slightly warmer areas
permanently frozen ground separated by unfrozen less cold areas
slightly warmer zones due to the proximity of surface water

Question 7

what is the annual mean temperature of areas of discontinuous permafrost?

Answer 7

1 and -5 degrees

Question 8

what is sporadic permafrost?

Answer 8

found when mean annual temperature is just below 0 degrees, and the summer temperatures reach several degrees above, bus isolated pockets of permanently frozen ground remain below the surface

Question 9

what is the active layer?

Answer 9

summer temperatures sufficient to melt the surface layer of permafrost. This layer can be very mobile. It varies in thickness depending on the latitude and vegetation cover.

Question 10

where can periglaciated environments be found?

Answer 10

in the northern hemisphere
above 66.5 degrees of latitude

Question 11

what is the result of freeze thaw action in periglaciated areas?

Answer 11

screes develop at the foot of slopes as a result of frost shattering. On relatively flat areas, extensive spreads of angular boulders are left- knows as blockfield or felensmeer.

Question 12

where does nivation take place in periglaciated areas?

Answer 12

beneath patches of snow in hollows, particularly on north-east facing slopes.

Question 13

what happens during nivation in periglaciated areas and what does it form?

Answer 13

physical and chemical weathering operates under the snow, causing the underlying rick to disintegrate. As the snow melts in summer, the weathered particles are moved out downslope by the meltwater and SOLIFUCTION. Leads to formation of NIVATION HOLLOWS which can become CORRIES.

Question 14

what is solifuction?

Answer 14

1. when the active layer thaws in the summer, excessive lubrication reduces friction between soil particles
2. this leads to solifluction sheets or lobes often forming terraces on the side of the valley

Question 15

what is frost heave?

Answer 15

stones have a different specific heat capacity than finer sediment. stones under surface are pushed up through finer material which freezes and thaws until they eventually reach the surface where they fall down a mound forming patterns in the ground.

Question 16

what is a pingo?

Answer 16

dome-shaped hill that is commonly up to 500m in diameter and up to 50m in height

Question 17

where are pingos found?

Answer 17

common in periglacial areas that are characterised by permafrost and a seasonally changing active layer

Question 18

what is at the core of a pingo?

Answer 18

an ice lens of varying size and the surface layer is made of soil often topped with vegetation
this surface can contain cracks as a result of ground swelling

Question 19

where are closed systems pingos found?

Answer 19

typically to the Mackenzie River delta in Canada

Question 20

closed system pingos stage one

Answer 20

-on low-lying areas where permafrost and continuous permafrost can be found
1. in this area of Canada there are hundreds of small lakes where water is trapped in small depressions during summer because the ground underneath is permanently frozen and effectively impermeable
2. over the winter, ground water underneath the lake sediments within the talk can be trapped by ice from the lake surface, as the lake freeze and advancing permafrost within the ground

Question 21

close system pingos stage 2

Answer 21

1. this decrease in temperature causes this groundwater to freeze into an ice lens, which grows over time as water freezes to the ice lens due to the increase in the hydrostatic presser
2. this causes the sediment above to bulge upward into the characteristic pingo shape

Question 22

what is hydrostatic pressure?

Answer 22

the pressure of fluid exerted by a confined fluid, such as water under or in a glacier

Question 23

where are open system pingos formed?

Answer 23

occur in valley bottoms of discontinuous permafrost and talik where water form slopes collects under gravity and becomes trapped between the descending freezing plane is the active layer and the surrounding permafrost.

Question 24

open system pingos formation.

Answer 24

water from slopes becomes trapped between the descending frozen layer and active layer and the surrounding permafrost. It freezes and expands under artesian pressure- promoting growth of an ice lens- pushes land above it as it expands. water underneath the permafrost can move through talik and the permafrost due to CAPILLARY ACTION and ARTESIAN PRESSURE causes water to migrates to lens and freezing pushing ground further upwards.

Question 25

where are open system pingos common?

Answer 25

east greenland

Question 26

what is capillary action?

Answer 26

movement of water through talik

Question 27

what is artisian pressure?

Answer 27

draws moisture to the lens

Question 28

what is a collapsed pingos called?

Answer 28

ognip

Question 29

how can pingos rupture?

Answer 29

if they become too large and if the ground cracks it exposes the ice lens to the suns energy and atmosphere, this can cause them to melt then collapse

Question 30

what happens after a pingo collapses?

Answer 30

it leaves a ruptured pingo with a depression and in the middle of that can fill with water and a lake, and a rampart around the edge that it price to the mass wasting process of solifluction