1. Destination: Understand fluvioglacial
processes and landforms
Routes: Identify, describe and explain
the formation of meltwater channels,
eskers, kames, kettle holes, outwash
plains and varves

2.  Fluvio – rivers
 Glacial – glaciers
 Glacial meltwater erosion and deposition

3. What words could you use to describe the following?

4. • Angular?
• Sub-rounded?
• Sorted?
• Unsorted?
• Stratified (in layers)?
• Unstratified?
• Mainly gravel & sand?
• Clay & boulders?
Why might they
be different?

7. Subglacial stream
A stream that flows
beneath a glacier, and
which usually cuts into
the ice above to form a
tunnel.
Large subglacial stream channel
that formed beneath the glacier
Pastaruri, Peru when an ice-
dammed lake drained.
Fluvioglacial landforms are created by the
meltwater from glaciers, largely through
deposition but also by erosion

8.  When glacial ice melts, water runs out as
streams of meltwater
 Warm-based glaciers produce lots of
meltwater
 Surface meltwater filters through the glacier
(e.g. through crevasses or moulins) and flows
through tunnels underneath the glacier
before running out of the snout

9.  Put moulin dye video clip in here
 Wikipedia image of moulin

11.  Meltwater streams cause erosion in the same
way as normal rivers – but they cause more
erosion than rivers the same size
 The confinement of the ice means they flow
quickly under pressure, so they can carry lots
of material which can erode the landscape
 The streams form deep troughs in the
landscape called meltwater channels (wide
and deep)
 After the glacier has retreated, the deep
meltwater channels are left with shallow
streams running through them

12. Glacier
milk
Meltwater
from a
glacier,
which
commonly
has a milky
appearance
from
suspended
fine
sediment.
Meltwater from Vadret da Morteratsch, Grisons, Switzerland
Photo
taken on a
July
morning
Photo taken
in the
afternoon
after
ablation and
subsequent
runoff had
both
increased
considerably

13.  The melting of ice produces a great deal of
water that has the ability to carry much
debris.
 The water often flows under pressure so is
turbulent and of a high velocity.
 It can pick up and transport more material
than a river of a similar size.
 This water, with its load, is responsible for
the creation of deep subglacial valleys with
potholes.

14.  When the meltwater discharge decreases, the
loss of energy causes debris to be deposited.
 Heavier particles are dropped first, resulting in
sorting of the material.
 Deposits may be found in layers (stratified) as a
result of seasonal variations in meltwater flow.
 The main features produced by fluvioglacial
deposition are eskers, kames and the outwash
plain.
 Lakes on the outwash plain may have deposits in
them called varves.

16. Features of lowland glaciation
Area of fluvio-glacial landforms

17. Braided stream A relatively shallow stream with
many branches that commonly recombine and migrate
across a valley floor. Braided streams typically form
downstream of a glacier.
Tasman River, South Island, New Zealand, fed by Tasman Glacier off the picture to
the right, and the Hooker and Mueller glaciers in the valley in the centre background.

18.  Long ridges of material running in the
direction of ice advance
 Sinuous form, 5-20m high
 Sorted, coarse material, usually coarse sand
and gravel
 Often stratified (in layers)

19. Esker A long, commonly sinuous ridge of sand
and gravel, deposited by a stream in a
subglacial tunnel.
Esker (arrowed) in NW Spitsbergen, Svalbard,
Norway The ridge is about 3 m high

20.  Deposits made by subglacial streams.
 Channel of stream is restricted by ice walls, so
there is considerable hydrostatic pressure which
enables a large load to be carried and also
allows the stream to flow uphill for short
distances.
 Some eskers therefore run up gentle gradients.
 Bed of channel builds up above the surrounding
land and a ridge is left when the glacier retreats
during deglaciation.
 Sometimes, the ridge of an esker is combined
with mounds of material, possibly kames. This is
called a beaded esker.

22.  Mounds of fluvioglacial material
(sorted, often stratified, coarse sands and
gravel).
 Deltaic deposits left when meltwater flows
into a lake dammed up in front of the glacial
snout by recessional moraine deposits.
 When the ice retreats further, the delta
kame often collapses.
 Kame terraces are frequently found along
the side of a glacial valley and are the
deposits of meltwater streams flowing
between the ice and the valley side.

23. Kame terrace Valley-side terrace or bench
formed by the deposition of fluvial sediment
along the margin of a glacier. The terrace is left
stranded on the hillside after the glacier has
receded.
Kame terrace

24.  Kames – supraglacial material
 Eskers – subglacial material

26.  Draw a labelled sketch to show the
characteristics of eskers (4 marks)
 Explain the formation of eskers (5 marks)

29.  Found in front of the glaciers snout.
 Deposited by meltwater streams issuing from
the ice.
 Consist of material brought down by the
glacier and then picked up, sorted and
dropped by running water beyond the
position of the ice front.
 Coarsest material travels shortest distance
before being deposited.
 Deposits are layered vertically, which
reflects the seasonal flow of meltwater
streams.

30. Outwash plain (aerial view)
A relatively flat spread of debris deposited by meltwater streams
emanating from a glacier
Outwash plain in front of Thompson Glacier, Axel Heiberg Island, Canadian Arctic

31.  Meltwater streams that cross the outwash plain are
braided.
 This happens as the channels become choked with
coarse material because of marked seasonal
variations in discharge.
 The outwash plain often contains small depressions
filled with lakes or marshes – kettle holes.
 Kettle holes form when blocks of ice, washed onto
the plain, melt and leave a gap in the sediments.
 The gap then fills with water to form a small lake.
 Aquatic plants become established in the lakes which
leads to the development of a marshy area, then
peat.

32. Outwash plain (ground view)
A relatively flat spread of debris deposited by meltwater
streams emanating from a glacier.
Glaciologist crossing an outwash plain in front of Midre Lovénbreen in NW
Spitsbergen, Svalbard

35. Kettle holes
Kettleholes form in the following way:
 As the glacier retreats it may leave large
blocks of buried ice.
 This ice slowly thaws over time and the
covering gravel collapses leaving a
depression.
 These depressions are called kettle holes.
 If the depressions are deep enough to tap
the water table a kettle hole lake forms.

37. Kettle (red arrows) (or kettlehole) A self-contained bowl-
shaped depression within an area covered by glacial stream
deposits, often containing a pond. A kettle forms from the burial
of a mass of glacier ice by glacial or stream sediment, followed
by its subsequent melting.
Kettles in the forefield of Glacier du Mont Miné, Valais, Switzerland.

38. Varves
A varve is a distinct layer of silt lying on top of a layer of
sand, deposited annually in lakes found near to glacial
margins
The coarser, lighter coloured sand is
deposited during late spring when
meltwater streams have their peak
discharge and are carrying their
maximum load.
As discharge
decreases towards
autumn when
temperatures begin
to drop, the
finer, darker silt will
settle.

39.  Lakes on the fringe of the ice are filled with
deposits that show a distinct layering.
 A layer of silt lying on top of a layer of sand
represents one years deposition in the lake – a
varve.
 The coarser, lighter coloured layer is the spring and
summer deposition when meltwater is at its peak
and the meltwater streams are carrying maximum
load.
 The thinner, darker coloured and finer silt settles
during autumn and winter as stream discharge
decreases and the very fine sediment in the lake
settles to the bottom.
 A good indicator of age of lake sediments and past
climates.

41. Proglacial lakes and overflow channels:
 Glacial meltwater has great erosive power because of
its volume and the large amounts of debris it
contains.
 During deglaciation, lakes develop on the edges of
the ice, some occupying large areas.
 Overflows from these lakes which cross the lowest
points of watersheds will create new valleys.
 When the ice damming these meltwater lakes totally
melts, many of the new valleys are left dry, as
drainage patterns revert to the preglacial stage.
 In certain cases, however, the postglacial drainage
adopts them, giving rise to new drainage patterns.

42.  Large meltwater lakes of this kind occurred
in the Midlands (Lake Harrison), the Vale of
Pickering in North Yorkshire (Lake Pickering)
and the Welsh borders at the end of the last
glaciation.
 The River Thames is thought to have
followed a much more northerly course
before the Quaternary – its modern course
formed when ice filled the northern part of
its basin and forced it to a different route.

43. Proglacial lake
A lake developed immediately in front of the glacier, commonly
bordered by the mounds of unconsolidated deposits that
characterise the terminal zone of a glacier.
Proglacial lake at Sheridan Glacier near Cordova, Alaska.

45. Summary
diagram –
features
produced by
glaciation

46.  Assess the role of meltwater erosion and
deposition in the formation of fluvioglacial
landforms (15 marks)

47.  Draw a labelled sketch to show the
characteristics of eskers (4 marks)
 Explain the formation of eskers (5 marks)