Here are the key periglacial processes likely occurring around the glacier shown in Figure 2: - Frost shattering of rock producing scree slopes at the base of valley sides due to repeated freezing and thawing. - Solifluction occurring on valley sides within the active layer, transporting fine material downslope and leaving lobes and terraces. - Nivation occurring in hollows beneath snowpatches on north-facing slopes, deepening the hollows through frost action and meltwater erosion. - Patterned ground such as stone stripes forming in better drained areas subjected to freeze-thaw cycles. - Fluvial erosion by meltwater streams flowing from the glacier, causing erosion and leaving braided

1. Learning destination: understand what
permafrost, frost heave, groundwater
freezing, nivation and solifluction are and
what landforms they create
Routes: Identify, describe and explain the
formation of nivation hollows, ice wedges,
patterned ground, pingos and solifluction
lobes

2.  What glacial feature does this Wordsworth poem
describe?
“As a huge Stone is sometimes seen to lie
Couched on the bald top of an eminence;
Wonder to all who do the same espy,
By what means it could thither come, and whence;
So that it seems a thing endued with sense:
Like a Sea-beast crawled forth, that on a shelf
Of rock or sand reposeth, there to sun itself”
W Wordsworth 1807 The Leech Gatherer

3.  Areas that experience a cold climate, with
intense frost action and the development of
permafrost
 Aka tundra areas
 20-25% of the Earth‟s surface is periglacial, e.g.
northern North America and Russia above the
Arctic Circle
 Experience conditions close to glacial (near an
ice sheet e.g. Greenland). Peri = near.
Consistently below 0 degrees celsius.
 Temporally close to glacials (e.g. Highland
Scotland)
 Very cold climate with distinctive landforms
 May exhibit temperate climates today

4. Where are periglacial environments?
• High altitudes – around ice masses in mountain ranges. Also in
high altitude plateau areas e.g. the Tibetan plateau and Bolivian
plateau
• High latitudes e.g. northern Asia, North America and northern
Europe
• Continental interiors – due to continentality, e.g. Siberia, central
Asia

5.  Permanently frozen ground
 Impermeable
 Subsoil temperatures must remain below zero for
2 years or more for permafrost to develop
 The extent, depth and continuity of the
permafrost layer varies through time according
to fluctuations in climate
 During summer, when air temperatures are
above freezing, the surface layer thaws to form
an active layer up to 4m deep.
 The active layer gets easily waterlogged due to
frozen ground beneath so will easily flow if there
is a gradient - solifluction

6.  Continuous – found in coldest regions (mean
below -5) e.g. the Arctic where there is little
thawing even in summer. Affects soil and rock to
a depth of 700m in Canada and twice that in
Siberia
 Discontinuous – found in slightly warmer regions
where freezing conditions do not penetrate to
such great depths (20-30m). Discontinuous due
to breaks around rivers, lakes and the sea.
Patches are frozen.
 Sporadic – mean annual temperatures are around
or just below freezing, so permafrost appears
only in isolated spots

9.  Define the term „periglacial‟ – 2 marks (also
in June 2011)
 Explain the annual changes in the active
layer above the permafrost – 4 marks

11. Describe the distribution
of permafrost shown in
Figure 3 – 4 marks
June 2012

14. Blockfield
Felsenmeer

15.  Provides a great deal of erosive material in
glaciers, so already studied
 In periglacial areas, screes develop at the
foot of slopes due to frost shattering
 On relatively flat areas, extensive spreads of
angular boulders are left, known as
blockfield or felsenmeer (sea of rocks)
 E.g. the Glyders, North Wales

18. Patterned ground
Stone polygons
Stone stripes

19.  Results from the direct formation of ice
crystals in the soil as it starts to refreeze
 On freezing, fine-grained soils expand
unevenly upwards to form domes.
 As stones cool down faster than the
surrounding soil, small amounts of moisture
in the soil beneath the stones freeze and
turn to ice, expanding by 9% as they do so.
 By repeatedly freezing and thawing over
time, these ice crystals and lenses heave
stones upwards in the soil.

20.  In areas where temperatures fluctuate
between 0 degrees and -4 degrees C, the
frost heaving and subsequent thawing is able
to sort material to form patterned ground.
 The larger stones move outwards down to
the very low slopes of smaller domes because
of their weight.
 On gentler slopes stone polygons are
created, but where the ground is steeper
(greater than 6 ̊) the stones are dragged
downhill by gravity into more linear
arrangements known as stone stripes.

24. Describe the patterned ground shown in
Figure 2 and explain its formation – 6 marks

26. Pingos

27.  Freezing of water in upper layer of soil
where permafrost is thin or discontinuous
leads to the expansion of ice within the soil
 This causes the overlying sediments to heave
upwards into a dome-shaped feature known
as a pingo
 Less than 50m in height, 0.5km across, found
in sandier soils = open-system or East
Greenland type

28.  Closed-system pingos or Mackenzie type pingos
are more typical of low-lying areas with
continuous permafrost
 On the site of small lakes, groundwater can be
trapped by freezing from above and by the
permafrost beneath as it moves in from the
lakeside
 Subsequent freezing and expansion of trapped
water pushes the overlying sediments into a
pingo form
 If the centre collapses it may infill with water to
form a small lake
 Over a thousand of these pingos have been
recorded in the Mackenzie delta (Canada)

30.  Draw 3 diagrams:
1. Formation of an open-system (East
Greenland) type pingo
2. Formation of a closed-system (Mackenzie)
type pingo
3. A ruptured pingo

32.  Draw a labelled sketch to show
characteristics of a pingo and suggest an
explanation for its formation – 7 marks

35. Ice wedges
Ice wedge polygons

36.  Refreezing of the active layer during winter
causes the soil to contract and cracks open up on
the surface
 During melting the following summer, the cracks
open again and fill with meltwater and its
associated fine sediment, which helps to
partially fill the crack
 Repetition widens and deepens the crack to form
an ice wedge up to 1m wide and 3m deep
 A near polygonal pattern is produced on the
surface, similar to frost heave polygons
 Forms ice wedge polygons

39. Nivation hollows

40.  Occurs mainly between north and east facing
slopes beneath patches of snow in hollows
 Frost action below snow which involves
freeze-thaw and solifluction and meltwater
 Freeze-thaw disintegrates underlying rock
 During spring thaw, weathered particles
moved downslope by meltwater and
solifluction
 Leads to nivation hollows which may be the
start of corrie development

42. Solifluction lobes

43.  Summer thaw in the active layer releases a
lot of meltwater
 Water cannot percolate downwards due to
frozen ground so it saturates the soil
 It reduces internal friction between particles
making the soil mobile
 The soil flows even on slopes of only a few
degrees
 Leaves behind rounded tongue-like features
forming terraces on the side of valleys –
solifluction lobes

46.  Stepped features below vegetation, pushed
forward and rolled under like Caterpillar
truck
 Where vegetation is sparse, stones heaved to
the surface are pushed to the front of the
advancing lobe and form a small stone bank
at the front of the lobe
 Many parts of southern Britain experienced
these conditions during the Quaternary ice
age and these deposits, which filled in
valleys are known locally as head (coombe in
chalky areas)

48.  Periglacial areas are often open and sparsely
vegetated. This means that erosion by water
and wind can be high.
 Water erosion is seasonal, occurring in
mainly spring and summer when the active
layer melts.
 This can bring short periods of high discharge
in rivers bringing high levels of fluvial
erosion.
 Drainage is braided due to high amounts of
debris being carried by meltwater streams.

50.  Unobstructed winds reach high velocities
 Cause erosion through abrasion
 They dislodge fine, unconsolidated materials.
 Result in grooved and polished rock surfaces
and in stones shaped by the wind, called
ventifacts
 Fine material of outwash plain is picked up
and carried long distances
 It is deposited elsewhere as areas of loess
 Loess is found in many parts of North
America and Eurasia, just south of the
Pleistocene ice sheet limit

53.  Outline periglacial processes likely to be
occurring around the glacier in Figure 2 – 5
marks