In this unit you will learn:
1. The formation of erosional and depositional features in
glaciated and coastal landscapes.
2. To identify features on an OS map.
3. Rural land use conflicts and their management related
to glaciated and coastal landscapes
Glaciation is the study of ice and
its impact on the environment.
When people talk about the Ice
Age, they are often referring to
the most recent glacial period,
which peaked about 21,000 years
ago and ended about 11,500 years
ago.
During that time the Northern and
Eastern parts of the British Isles
were covered in ice.
Glaciers were formed which move
down valleys with great erosive
power.
These glaciers carved new
scenery.
Ice Age Cycle
clip
Ice ages happen due to
periods of global
cooling.
* You will revisit this in
the climate change and
atmosphere unit.
SNOUT = the end of a glacier.
CALVING = when large chunks of the glacier break off.
Aim: To explain the formation of a glacier
and identify features of glacial erosion.
Watch the video
clip on the
following slide.
Snow builds up in
layers.
Air is squeezed out
to form ice.
• As more snow falls the pressure makes the
earlier snowflakes melt.
• Repeated melting and re-freezing forms
granules called firn and neve.
• Further compression forms larger crystals of
glacial ice.
• It can take 30 to 40 years for snow to form
dense glacial ice.
• It moves downslope under its own weight.
Can you name features of glaciated scenery?
TASK: Glue this into your notes.
Identify the features below.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Pyramidal Peak
Arête
Corrie
Tarn
Alluvial fan
Ribbon Lake
Truncated spur
Misfit stream
Hanging Valley
U-shaped valley
Lateral moraine
Features are created
due to glacial
processes of
erosion. These are
the different ways
the ice erodes the
land:
1. Ice plucking
2. Abrasion
3. Frost
shattering/
freeze thaw
weathering
• ICE PLUCKING = ice freezes around the rocks
and pulls/plucks them away when the glacier
moves. Ice sticks to the rock.
• ABRASION = when rocks rub against other
rocks the friction grinds them down like sand
paper.
Rocks act as
tools to erode
ABRASION
• FROST SHATTERING = water seeps into the
cracks in the rocks and expands when it turns
to ice. Repeated freezing and thawing
weakens the rock and it breaks into pieces.
Temperatures
>0 degrees
Temperatures
<0 degrees
Identify the
processes
that could
have caused
this.
•
•
•
•
•
•
•
Corrie
Pyramidal Peak
Arête
U- Shaped Valley
Hanging Valley
Truncated Spurs
Ribbon Lake
Aim: You must be able to explain the
formation of these features in detail.
Exam questions often ask for diagrams to
explain the formation of features.
• Snow collects in a North/N.East facing hollow.
As it is a more shaded aspect snow doesn't
melt as quickly. The snow compacts and air is
squeezed out to form glacial ice.
• The glacier moves downhill due to gravity.
• Melt water under the glacier lubricates
the ice and helps it to move.
• As the glacier moves, it pulls away rocks that
are stuck to the ice. Ice plucking forms a steep
back wall.
ROTATIONAL
SLIDING
• Exposed rocks are loosened by a process
called frost shattering. Broken rocks fall into
the glacier through crevasses.
• Rocks trapped at the bottom of the glacier
grind away other rocks like sandpaper. This is
abrasion and it deepens the hollow.
• A gap between the wall and the ice develops,
called a bergschrund.
• Most
erosion is
where the
weight of
the ice is
heaviest.
• Ice in a corrie has a rotational movement
which means that the front of the corrie is less
eroded, and a lip forms.
• After glaciation an over-deepened, armchair
shaped hollow with a steep back wall and
smooth sides remains. This is a corrie.
• It often fills with meltwater or rain to form a Tarn,
e.g. Red Tarn.
Aim: To explain the formation of
an arete and pyramidal peak.
Ben Nevis Arete
Ben Nevis Arete
• An arête is a narrow knife-edged ridge where
two corries have eroded back to back.
• That is, when the back walls of a corrie have
been eroded back so far that only a narrow,
knife-edged ridge separates them.
• The steep back walls are formed through ice
plucking and frost shattering.
Starter Task
Number the following: Glacier, ice plucking,
abrasion, frost shattering, rock lip, steep back
wall.
identify the features 1-4.
• Found where 3 or more corries are located in
the same mountainside.
• Plucking and freeze-thaw action at the
backwall of each corrie occurs to such an
extent that the rounded summit is eroded into
a sharp peak or point.
Q. Explain the conditions and processes
involved in the formation of a corrie. 5 marks
• You may wish to use an annotated diagram or
diagrams.
(2010 ppq)
Assess out of 5 marks.
Lesson Aim: To explain the formation
of a U-Shaped Valley.
Before Glaciation
A river meanders
around interlocking
spurs.
INTERLOCKING SPURS
• The build up of snow and ice during the Ice Age(s)
caused valley glaciers to move downhill under
gravity from their source in the mountains (corrie
glacier) following existing (V-shaped) river valleys
• The huge weight/volume of ice combined with
processes such as plucking, abrasion and rotational
sliding widened and deepened these valleys
• As the valley glacier advanced it abraded the former
interlocking spurs leaving truncated spurs and
steepened the sides of the valley/glacial trough
• The resulting U-shape of the valley left behind
when the ice melted may vary according to
rock hardness and the intensity of erosion.
• After glaciation a ribbon lake and misfit
stream tends to flow on the wide floor of the
valley. Also scree slopes (loose angular rocks)
can form at the base of the steep sides due to
frost shattering.
Stick this diagram into your notes.
Lesson Aim: To explain the formation of
a hanging valley.
• Hanging valleys are the product of different rates of erosion
between the main valley and the tributary valleys that enter it
along its sides.
• Hanging valleys are formed in the same way as U-shaped
valleys. These smaller tributary valleys, however, contained
much less ice and so the power to erode was less.
• As a result they were not eroded as deeply as the main valley,
so where they melt, the tributary valley was left ‘hanging
over’ the main valley.
• After the ice age, when rivers again flowed a waterfall would
very often flow over the hanging valley.
How was this
feature formed?
More resistant, hard
rock takes longer to
erode.
The ribbon lake is
dammed by a rock bar.
The glacier easily
erodes the soft rock
forming a rock basin.
Moraine may be
deposited by the
glacier which will
also dam the lake.
• At some points in the U-shaped valley, glaciers erode more
deeply than elsewhere.
• This might have been because the rock was softer and
more easily eroded or because the ice was thicker at this
point and therefore more powerful.
• Where ice did this, it would create an over deepened
hollow which filled with melt water after glaciation to
become a Ribbon Lake.
• The lake takes on the same shape as the valley in which it
was formed – so tends to be long and quite narrow.
• Ribbon lakes can occur when terminal
moraine or rock barrier stretches across the
valley floor, forming a dam.
• Ribbon lakes formed after the ice age as
outflowing streams were dammed by the
moraine or filled the over deepened parts of
the valley floor.
• Roches moutonnée
often have steep,
jagged faces created by
plucking on the lee
(far) side and a gradual
incline which is
smoothed and polished
by abrasion on the
other (stoss) end. It
may have striations on
it indicating the
direction of glacier
movement.
3
4
•
•
•
•
•
•
•
Outwash plains
Erratics
Moraine
Eskers
Drumlins
Kames
Kettle holes
Materials carried by the glaciers are deposited in two main ways;
• Glacial Deposits (unsorted) dumped from the melting ice, such
as moraines and till. These are jumbled mixtures of broken rock
material of many different sizes.
• Fluvo-glacial deposits (sorted) washed out of the ice by melt
waters, such as eskers. These are more rounded and have been
sorted by the action of the water, the heavier materials being
laid down first.
Lesson Aim:
• To explain the formation of an outwash plain.
• These are large areas of glacial sediment
deposited by melt water streams furthest
away from the glacial snout.
• They are formed from gravels, sands and clays,
the clays being furthest away from the snout
because the smaller particles are carried
furthest.
• Material that was already
deposited by older streams
and ice activity may be
reworked and sorted by the
streams forming the
outwash plain, and carried
beyond the original
maximum extent of the ice
sheet / glacier.
• Some idea of the former
extent of glaciation may be
seen from the thickness of
outwash plain sediments
which can be well in excess
of 50m thick.
OUTWASH PLAIN SUMMARY:
•
Melt water streams rush through the terminal moraine picking up rock pieces.
•
The streams then drop these pieces beyond the terminal moraine as they slow
down as they lose energy.
•
The largest pieces are dropped first and the smallest last.
These areas of sand and gravel, rounded and sorted by melt water are called
outwash plains.
• Moraine is a type of landform that is created when a
glacier deposits the material (till) that it has been
transporting. It is made up of unsorted angular rocks.
There are several types of moraine:
Lateral
Medial
Ground
Recessional
Terminal
• Lateral moraine is found on the sides of the glacier.
Scree, from frost shattering, is an important source.
• Medial moraine is found down the middle of the glacial surface
and occurs when the inner lateral moraines of two glaciers join.
• Ground moraine is found at the base (bottom) of the ice.
It is also called till or boulder clay.
• Boulder clay is glacial moraine consisting of thick clay with angular rocks.
The exact composition will depend on the rocks eroded by the glacier.
Boulder clay is sometimes called till.
• As the ice sheet advanced, it bulldozed loose
rock and soil in front of it.
• When the ice melted, the material was
dropped where the ice melted, building up
ridges of moraine.
• Terminal Moraine
is made up of
jagged pieces of
rock and are
unsorted (large
and small pieces
mixed together).
• It marks the
furthest extent of
the ice and forms
across the valley
floor.
Lesson Aim: Explain the
formation of eskers.
Eskers are long trails of moraine
deposited by rivers flowing through the
glacier. When the glacier melts the
material is deposited in a long line.
SUMMARY:
• A melt water stream flows in a tunnel
beneath a melting ice sheet.
• The stream carries and deposits
moraine filling up the tunnel.
• When the ice melts, a long ridge of
moraine is left in the shape of the
stream’s tunnel.
Q. Explain the formation of eskers.
Lesson Aim: Explain the formation of drumlins.
• Melting ice deposits large amounts of moraine.
• Drumlins are smooth, elongated mounds of material
formed parallel to the direction of ice movement.
• Often found in swarms. Drumlins form when ice is
moving.
• They consist of stones and clay, and are believed to
result from the load, carried by a glacier, becoming too
heavy and being deposited as it melted.
• Further forward movement of ice moulds the moraine
to form streamlined mounds.
• Drumlins have a steep upstream side called
"stoss", and a gently sloping "lee" side.
• Water is sometimes trapped between
drumlins causing lakes to form.
Q. Explain the formation of a drumlin.
3 marks.
Kettles are fluvioglacial
landforms occurring as
the result of blocks of
ice calving from the
front of a receding
glacier and becoming
partially to wholly
buried by glacial
outwash.
When the ice melts the
water is trapped.
You must be able to recognise glacial landscapes.
Re-cap – what features might you see on the
map?
Features you should be
able to recognise on a
map are:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Corrie
Tarn
Pyramidal Peak
Arête
Ribbon Lake
Misfit stream
Hanging Valley
U-shaped valley
Truncated spur
Corries are easy to spot on
maps.
• Contour lines are very close together showing
very steep land = steep back wall.
• The contour lines curve round due to the
armchair shaped hollow.
• They are often filled with a corrie lochan/tarn.
• Sometimes shown as, “Coire” or “Cwm”
Corrie
with
tarn
Corries
without
tarn
What feature forms when two corries form
back to back?
Arêtes
• 2 corries back to back
• Contour lines are very close together showing
very steep land = steep back wall.
• Ridge is shown by black rugged lines.
Pyramidal Peaks
• Can be difficult to spot
• 3 or more corries back to back
• Contour lines are very close
together showing very steep land
= steep back wall.
• Ridge is shown by black rugged
lines.
• “Summit” may appear.
U Shaped Valley
• Contour lines are very close together showing
very steep sides.
• White space in between shows flat land.
• Usually it has a ribbon lake or misfit stream.
Loose rocks often
found at the base of
steep cliffs = scree.
Misfit
Stream
Hanging Valley
• Smaller tributary valley joins onto
larger U-shaped valley.
• Usually has a waterfall.
Come out to the board and highlight the different
glacial features.
Come out to the board and highlight the different
glacial features found in the Lake District.
TASK: Identify the glaciated features using
map evidence.
Corrie
Remember!
Contour lines are very close
together showing very steep
land.
Arete
The contour lines are curved
showing a bowl-shape
Sometimes a tarn is evident
U-Shaped Valley
Where two corries form
back to back.
Contour lines are very close
together showing very steep
land. There is a long strip of
white in the middle showing
flat land.
The arete (ridge) is shown
as a black rugged line
2012 ppq
Study OS Map Extract number 1940/115: Snowdon (separate item), and Map
Q1.
(a) Describe the evidence which shows that Area A, shown on Map Q1, has
been
affected by the processes of glacial erosion.
You should refer to specific named features and make use of grid references.
2012 ppq