LITHOSPHERE
LANDSCAPE FEATURES RESULTING FROM GLACIAL AND
FLUVIOGLACIAL ACTION
Glacial
Action by ice
Erosion
Deposition
Corries
Arêtes
Pyramidal peaks
Hanging Valleys
Ribbon Lakes
Fiords
U-shaped valley
Ground Moraine
Moraine Ridges
Drumlins
Erratics
Fluvioglacial
Action by
Meltwater
Kames
Eskers
Outwash Plains
Before Glaciation
Corrie
Snow collects in the north
facing slopes in hollows as
more snow falls in winter than
melts in summer. North/northeast facing slopes are more
shaded so snow lies longer. As
more snow falls it is
compacted into ice(neve).
The ice will then begin to move
downhill due to gravity and
meltwater lubricating the
glacier.
During Glaciation
The erosive forces of the ice
erode the hillside, widening and
deepening the hollow. As the
glacier moves downhill it freezes
onto the back wall and tears rock
away eroding the steep backwall
by plucking, deepening and
widening the hollow into a basin
shape by abrasion. This is when
material trapped in the ice grinds
away at the solid bedrock below
like sandpaper. Rotational sliding
further deepens the central part of
the hollow floor as
gravity causes the ice to move.
Friction causes the ice to slow
down at the front edge of the
corrie, allowing a rock lip to form,
which traps water as ice melts,
leaving a lochan or tarn.eg Corrie
Cas
After Glaciation
Corrie formation
Corrie with tarn
Slide 74
Formation of an Arête
When two corries form back to back(use corrie note),
narrow ridges called arêtes form.eg Striding Edge
arete formation
Grib-Goch Arête, North Wales
Pyramidal Peak
Formation of a Pyramidal Peak
Arêtes
Matterhorn
When 3 or 4 corries erode back to
back around a hillside(use corrie
note), the arêtes between the
corries rise to a central peak,
called a pyramidal peak.eg Angels
Slide 71
Peak
Formation of a U-Shaped Valley (Glacial Trough)
V-shaped valley
U-Shaped Valley
Formation of U-shaped valley
Many small glaciers join to form a large main glacier which
deepens and widens and straightens a V-shaped valley,
forming a U-shaped valley. The valley is eroded by plucking
when the glacier freezes onto rocks and tears away when it
moves away. It is also eroded by abrasion when material
trapped inside the glacier scrapes away at the valley. This
main U-shaped valley has a wide flat bottom and steep sides
called truncated spurs which are eroded interlocking spurs.
On the flatter valley floor, a stream will meander called a
misfit stream. It is called this because it could never have
eroded the valley. If the U-shaped valley has been dammed
by an end moraine then a moraine damned lake is formed.
When a U-shaped valley meets the sea a fiord is formed
when sea water rose after the last ice age.
Hanging valley
Fiord picture
Glen Coe
Slide 82
Formation of a Hanging Valley
A small glacier flows down from a corrie eroding by
plucking and abrasion to join the main glacier found in the
main u-shaped valley. This smaller glacier doesn’t erode
as much as the main valley glacier and after the ice melts
this small tributary valley is left hanging above the main
valley. A small stream flows from the corrie and over the
hanging valley, forming a waterfall. At the bottom of the
waterfall an alluvial fan is formed by deposition.
Scree
In glaciated areas there is a constant process of freezethaw action (frost shattering). This is where water
enters cracks in the rock, freezes and expands by
9%. This forces the cracks slightly wider. This is
repeated many times and pieces of rock are broken
off. This builds up at the front of the slope as scree.
• Occurs on very steep slopes above 40˚.
• Where there is a lack of soil and vegetation.
• It is often found in areas of high altitude with low
temperature which causes frost-shattering or freezethaw action.
Scree
• Roots of trees can sometimes get into the cracks
in
the rock and cause the formation of scree.
LANDFORMS created BY GLACIAL DEPOSITION
GROUND MORAINE (Boulder Clay)
Ice carries moraine beneath it and on top of it. When the ice
melts it deposits the moraine. This forms a covering of soil
called boulder clay or till. This is clay soil with stones of
different sizes in it.
FORMATION OF TERMINAL MORAINE
Terminal Moraine
Animation
Direction of ice movement
A terminal moraine marks the maximum advance of a glacier
to the point where the climate was warm enough for it to
melt. This ridge was formed as ice bulldozed loose soil and
rock in front of it and from the constant deposition of melting
ice at the glaciers snout. All the material was deposited
where the ice melted building up a ridge. This ridge is made
up of unsorted rocks. This is called Terminal moraine
END MORAINES (or recessional moraines)
Erratic
Formed behind the terminal moraine. They mark interruptions
in the retreat of the glacier, when it remained stationary for long
enough to form a further small ridge.
ERRATICS (Rocks out of place)
Large boulders that are transported by glaciers and
deposited many miles away.
Fluvioglacial landforms
Fluvioglacial (action by meltwater)
Outwash Plain
When the glacier melts large amounts of water flows beyond
the terminal moraine. The water carries sand and gravel
beyond the terminal moraine, which is deposited by the river.
Larger pieces are dropped first followed by smaller ones.
What fluvioglacial feature is
this?
Eskers
A meltwater stream flows in a
tunnel beneath the melting ice
sheet. The stream carries and
deposits moraine filling up the
tunnel. When all of the ice melts
along ridge of moraine is left in
the shape of the stream’s tunnel.
These long ridges of deposited
material are called eskers.
Bedshiel Esker
Direction of flow
location of Bedshiel Esker
Drumlin
Drumlins are smooth, elongated mounds of material
formed parallel to the direction of ice movement. They
often consist of stones and clay, and are believed to
result from load, carried by the glacier, becoming too
heavy and being deposited. They owe their streamlined
shape to later ice movement.