Lesson 5: Periglacial Landscapes

Question 1

Define periglacial

Answer 1

Non-glacial cold environments, which are characterised by periods of extreme cold, dry conditions

Question 2

What are periglacial areas also called?

Answer 2

Tundra

Question 3

Define tundra

Answer 3

Term describing the treeless vegetation of dwarf shrubs, grasses, lichens and mosses

Question 4

Normal temps for tundra

Answer 4

3 down to -50 degrees

Question 5

Precipitation levels in tundra?

Answer 5

Under 600mm annually

Question 6

Define permafrost

Answer 6

Permafrost is permanently frozen ground where subsoil temperatures remain below 0°C for at least two consecutive years

Question 7

% of Earth with periglacial conditions?

Answer 7

20%

Question 8

% of Earth with periglacial conditions in Pleistocene?

Answer 8

33%

Question 9

Depth some permafrost can reach?

Answer 9

1500m

Question 10

Describe continuous permafrost

Answer 10

-Forms in the coldest areas of the world where mean annual temperatures are below -6°C
-Found at the highest latitudes
-Can extend downwards for hundreds of metres

Question 11

Describe sporadic permafrost

Answer 11

Mean annual temperature is only just below freezing and permafrost cover amounts of less than 50% of the landscape

Question 12

Describe discontinuous permafrost

Answer 12

-Shallower and permanently frozen ground is fragmented by patches of unfrozen ground (talik)
-The surface layer of the ground melts during the summer months

Question 13

What is isolated permafrost?

Answer 13

Less than 10% cover

Question 14

Effect of climate on distribution

Answer 14

Temperature and moisture determine the presence or absence, depth and extent of permafrost

Question 15

Effect of water bodies on distribution

Answer 15

Lakes tend to be warmer so remain unfrozen

Question 16

Effect of slope angle and aspect on distribution

Answer 16

Influencing solar radiation and therefore melting, freeze-thaw and wind

Question 17

Effect of ground surface/geology on distribution

Answer 17

Rock and soil types can determine degree and depth of permafrost

Question 18

Effect of vegetation cover on distribution

Answer 18

Can insulate the ground

Question 19

Describe freeze-thaw weathering/frost shattering

Answer 19

Water freezes in joints of rock and expands, weakening the rock, causing disintegration. Repeated

Question 20

% ice expands by

Answer 20

10%

Question 21

Landform from freeze-thaw

Answer 21

Blockfields - angular frost shattered rocks - flat surface
Scree - on slopes

Question 22

Describe solifluction

Answer 22

Downslope movement of saturated active layer under influence of gravity (gelifluction over impermeable permafrost)

Question 23

Landform of solifluction

Answer 23

Solifluction lobes - tongue-shaped feature at foot of slope

Question 24

Describe nivation

Answer 24

Processes weaken and erode the ground beneath a snow patch - freeze-thaw, solifluction, meltwater erosion

Question 25

Landform of nivation

Answer 25

Rounded nivation hollows formed in upland areas

Question 26

Describe frost heave

Answer 26

Freezing and expansion of soil water causes the upward dislocation of soil and rock
Ground freezes and large stones become chilled. Water below the stones freezes and expands pushing the stones upwards forming small domes

Question 27

Landforms of frost heave

Answer 27

Stone polygons

Question 28

Describe groundwater freezing

Answer 28

Water is able to filter down into the upper layers of the ground and freezes. Expansion of ice causes overlying sediments to heave upwards in a dome

Question 29

Landform of groundwater freezing

Answer 29

Pingo - ice-cored dome

Question 30

How high can some pingos be?

Answer 30

50m high

Question 31

Describe ground contraction

Answer 31

Dry areas of the active layer refreezes, ground contracts and cracks. Meltwater enters the crack during summer and freezes in winter. Repeated freezing and thawing widens joints

Question 32

Landform of ground contraction

Answer 32

Ice-wedge polygons - large-scale polygonal patterns on the ground surface

Question 33

Describe aeolian action

Answer 33

Due to limited vegetation cover, wind is able to pick up and transport fine, dry sediment from ground surface

Question 34

Landform of aeolian action

Answer 34

Loess - accumulation of wind-blown deposits

Question 35

Describe meltwater action

Answer 35

Thawing creates meltwater which erodes stream or river channel. Refreezing at the onset of winter causes reduction in discharge and sediment deposition in channel

Question 36

Landform of meltwater action

Answer 36

Braided streams - multiple channels separated by islands of deposited material

Question 37

Example of blockfields/screeslopes

Answer 37

Canadian shield / Baffin island
Northern Manitoba

Question 38

Example of solifluction lobe

Answer 38

Yukon, Canada

Question 39

Example of nivation hollows

Answer 39

Dovrefjell, Scandes Mt, Norway

Question 40

Example of stone polygons

Answer 40

Chic-Choc Mountains, Quebec, Canada

Question 41

Example of pingo

Answer 41

Ibyuk Pingo, Mackenzie Delta, Canada

Question 42

Example of ice wedge polygons

Answer 42

Beaufort Sea Coastline, Yukon, Canada

Question 43

Example of loess

Answer 43

Cypress Hills, Alberta, Canada

Question 44

Example of braided streams

Answer 44

Yukon river, Canada

Question 45

What are the two types of pingo?

Answer 45

open and closed

Question 46

Beyond what angle does the ground have to be for patterned ground not to occur?

Answer 46

30 degrees

Question 47

What can the height and diameter of pingos be?

Answer 47

30-70m in height
100-500m in diameter