Transcript 1. Lithosphere

LITHOSPHERE
GLACIATION
Introduction
Higher Geography
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LITHOSPHERE
 As more snow falls the
pressure makes the earlier
snowflakes melt.
INTRO
GLACIATION
Repeated melting and
re-freezing forms
granules called firn or
névé.
 Further compression
forms larger crystals of
glacial ice.
 It can take 30 to 40
years for snow to form
dense glacial ice.
 Gravity now moves the
glacier downslope.
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LITHOSPHERE
INTRO
GLACIATION
Ice erodes in the upland
areas using three main
processes and creates a
number of interesting
features
The products of erosionmoraine and other materialare transported to lower
ground where they are
deposited in areas in
specific shapes.
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LITHOSPHERE
EROSION
GLACIATION
PROCESS 1 Freeze-thaw/ frost shattering
Water from
melted snow
collects in cracks
and crevices in
rocks above
glaciers.
At night
temperatures
drop below
freezing and the
water changes
into ice as it
expands by 9%.
Water expands when
frozen and forces the
crack wider. When it
warms, ice melts and
the wider crack can hold
even more water.
After several
sessions, the rock
shatters.
 Sharp, angular pieces
of rock called scree fall
to the foot of the
slope.
This is a repeated
process
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LITHOSPHERE
EROSION
GLACIATION
PROCESS 2-Plucking
Glacial ice
freezes into the
cracks and
crevices made by
the freeze-thaw
process and as
the glacier
moves, loose
pieces of rock
are pulled or torn
out.
Note; This rock has joints
and bedding planes!
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LITHOSPHERE
EROSION
GLACIATION
PROCESS 3-Abrasion
Abrasion occurs when pieces of rock debris that are
embedded in the ice rub away at the rocks on the
valley floor and sides like sandpaper.
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LITHOSPHERE
EROSION
The rock is scratched, polished,
smoothed and eventually worn away
by the scouring action.
GLACIATION
Striations are
scratches made on
the existing
surface by rocks
that are embedded
in the bottom of
the glacier as it
moves forward.
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LITHOSPHERE
Features of
erosion
GLACIATION
CORRIES
Snow collects in hollows, especially on the less sunny
north and east facing slopes, turns to glacial ice and
moves downwards under the force of gravity
Rocks are plucked out and the hollow is widened by
abrasion to become a corrie.
A corrie is a deep, rounded hollow with a steep back wall.
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LITHOSPHERE
Features of
erosion
GLACIATION
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LITHOSPHERE
Features of
erosion
GLACIATION
Formation of a corrie
Describe and explain the formation of a corrie
8 marks
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LITHOSPHERE
GLACIATION
Before:
During the ice age and especially in the winter months
snow will gather on natural hollows in the landscape.
This gathering of snow usually occurs in the less sunny
north and east facing hills as it has less sun the
glacier does not have a chance to melt.
During:
The weight of the glacier turns the snow into ice and
once the ice reaches an uneven equilibrium it will start
to move downhill by gravity. When moving the glacier
erodes the landscape through plucking and abrasion
(here explain plucking and abrasion). These processes
deepen and widen the hollow. As the glacier moves
some ice will still be stuck to the back wall making the
bergschrund.
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LITHOSPHERE
GLACIATION
After:
Frost shattering still occurs once the ice age has left.
(explain frost shattering). This makes the jagged
summit and means scree continues to form in the Corrie
Lochan. Morraine left by the glacier can hold in the
water at the edge of the corrie.
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LITHOSPHERE
Features of
erosion
GLACIATION
Back
wall
scree
lip
Once the glacier retreats, the corrie may be filled
with water. A small, generally circular loch is
formed. This is known as a tarn or corrie lochan.
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LITHOSPHERE
Features of
erosion
GLACIATION
On an OS map,
corries are shown
as horseshoeshaped features.
scree
N
Note the contours are
very close together,
especially on the steep
backwall. Note also the
bare rock symbol.
Note the eastfacing aspect;
snow lasts longer
before melting.
tarn
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LITHOSPHERE
Features of
erosion
GLACIATION
Red Tarn
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LITHOSPHERE
Features of
erosion
GLACIATION
ARETE
An arete is a narrow, sharp-edged ridge
which forms the side walls of corries or
separates different glacial valleys.
Continually eroded by frost shattering. 16
LITHOSPHERE
Features of
erosion
GLACIATION
On a map an arete
is hard to see. It is
a long ridge between
to corries or
valleys.
The red lines mark
the spines of the
three aretes.
= arete
These corries and aretes
are in the Cairngorms.
bare rock
scree
horn
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LITHOSPHERE
Features of
erosion
GLACIATION
Striding Edge
Striding Edge
arete on
Helvellyn,
Lake District
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LITHOSPHERE
Features of
erosion
GLACIATION
MATTERHORN
Pyramidal peaks are also called horns.
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Corrie formation
LITHOSPHERE
GLACIATION
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Formation of a pyramidal peak
LITHOSPHERE
arête
tarn
The Ridge is the
ARETE
GLACIATION
Pyramidal peaks
are formed when
three or more
corries cut
backwards into the
same mountain.
corrie
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LITHOSPHERE
Features of
erosion
GLACIATION
Stages in the formation of a U-shaped valley
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LITHOSPHERE
GLACIATION
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Features of
erosion
GLACIATION
These are the actions that form this feature.
LITHOSPHERE
a) A glacier flows into an earlier 'V' shaped valley with
interlocking spurs.
b) The glacier abrades and plucks the sides and floor of
the river valley.
c) The valley is greatly deepened, widened and
straightened.
d) When the ice melts the valley is 'U' shaped with
truncated spurs.
e) It now has very steep sides and a fairly flat floor.
f) Any rivers are called 'misfit streams’ because they
are far too small to have cut the valley.
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LITHOSPHERE
Features of
erosion
GLACIATION
Truncated spurs
Former hill spurs are ‘truncated’- their ends are cut
off by the ice action to form steep, sheer cliffs.
The yellow lines
show where the
spurs were
before they were
chopped off!
Note how they
defined a Vshaped valley.
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LITHOSPHERE
Features of
erosion
GLACIATION
A U-shaped valley in Canada.
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Features of
erosion
LITHOSPHERE
When a glaciated valley is
submerged or drowned by a
rise in sea level, a fiord is
formed.
GLACIATION
The sea lochs of western
Scotland are the best
examples of fiords in the
British Isles.
Fiord/fjord
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LITHOSPHERE
Features of
erosion
GLACIATION
A hanging valley
Vertical erosion in the main
glacier is far greater than in
the tributary glaciers. So
the valleys are not the same
depth.
After the glacier has
retreated, rivers flowing
down the tributary join the
main valley via a waterfall
Can you spot the river
delta,too?
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LITHOSPHERE
When a glacier
moves along the
valley, some
parts are
deepened more
than others due
to softer rock.
Features of
erosion
GLACIATION
When the glacier
retreats, the
deepest parts fill
with water and
become lakes.
Ribbon lakes
The English Lake
District owes its
character to these
narrow ribbon lakes
along its valley
floors.
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LITHOSPHERE
An alluvial fan
Erosion/
deposition
GLACIATION
Caused when a
stream falling from
a side valley
reaches flatter
ground on the valley
floor.
Material is dropped
at the ‘break of
slope’ to form this
fan shape.
alluvium = silt deposited by a river
(This is really a
depositional feature.)
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LITHOSPHERE
A crag and tail
Plug of
volcanic
rock
Erosion/
deposition
GLACIATION
Edinburgh Castle
tail
These are partly erosional, partly depositional features.
The rock face facing the ice is steepened by glacial
erosion. Softer rock on the other slope is protected
from erosion to form a tail of boulder clay.
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LITHOSPHERE
deposition GLACIATION
TYPES OF MORAINE
Lateral moraine is found on
the sides of the glacier.
Scree, from frost
shattering, is an important
source.
Ground moraine is
found at the base
(bottom) of the ice.
It is also called till
or boulder clay.
Supra-glacial
Englacial moraine is found
inside the ice itself.
Medial moraine is found
down the middle of the
glacial surface and occurs
when the inner lateral
moraines of two glaciers
join.
Terminal moraine is found
in front of the snout of
the glacier if it is
stationary. It represents
the maximum advance of
the ice.
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LITHOSPHERE
deposition GLACIATION
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LITHOSPHERE
Terminal moraine
deposition GLACIATION
Snout of glacier
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LITHOSPHERE
GLACIATION
Before the ice melts
At the front of the glacier (known
as the snout)
a large pile of rocks and boulders
has been
“bulldozed” into a large pile.
LITHOSPHERE
After the ice has melted
GLACIATION
The glacier has now gone, and a pile of rocks and
stones known as terminal moraine is left.
Sometimes this mound can block streams from a
melting glacier, and moraine-dammed lakes are
formed.
LITHOSPHERE
ERRATICS
deposition GLACIATION
Erratics are large rocks
that are completely
different from the type
of rocks on which they
rest
They were carried
by the ice-sheet,
sometimes for
hundreds of
kilometres
and then
deposited.
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LITHOSPHERE
deposition GLACIATION
ESKER
Glacial streams are found
under the ice.They are
loaded with debris (sand
and gravel) carried by the
meltwater.
As the ice retreats, the
river deposits its load.
The built-up river bed is
called an Esker.
This river has dried up!
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LITHOSPHERE
deposition GLACIATION
An esker is a steep-sided, long, winding ridge, made
up of gravel and sand. Most are tree-covered.
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LITHOSPHERE
DRUMLIN
Drumlins are smooth,
rounded
mounds of ground
moraine.
The steep (stoss)
side faces the
direction the ice
moved from.
Drumlins often occur
in swarms or groups
on the valley floor.
deposition GLACIATION
Side view
Plan view
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Exam style questions
LITHOSPHERE
GLACIATION
Question 1
Corries are landscape features present in
glaciated upland areas.
Explain the conditions and processes involved
in the formation of a corrie. 8 Marks
You may use diagrams to illustrate your answer.
Fully annotated diagrams can receive full
marks.
LITHOSPHERE
GLACIATION
Question 2
As a glacier moves downhill it can create a
massive glacial trough.
Explain the conditions and processes
involved in the formation of a glacial
trough.
You may use diagrams to illustrate your
answer. Fully annotated diagrams can
receive full marks.
LITHOSPHERE
GLACIATION
Question 3
Terminal moraine can be found at the end of
the glacier.
Explain how it forms, the conditions of the
land and what the land can be used for after
the glacier retreats.
You may use diagrams to illustrate your
answer. Fully annotated diagrams can receive
full marks.