Mr Gallacher’s Glaciation Notes- Erosion, Deposition and Land Management
1. Processes of Erosion
Plucking
Plucking creates steepness. Plucking is when the ice freezes onto the rock face and
pulls large chunks of rock away, as the ice moves downhill.
Abrasion
Abrasion creates deepness and smoothness. Abrasion is when rocks trapped between
the ice and the rock face scrape along the rock face, wearing away the rock. Abrasion
is like the action of sand paper.
Freeze-Thaw OR Frost Shattering
Freeze thaw or frost shattering is when water enters the pores or cracks in a rock.
Repeated heating and cooling creates a freeze thaw action. This causes the crack in the
rock to get bigger, until it eventually breaks and shatters.
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2. Formation of a Corrie
Before Glaciation
1. Temperatures: begin to drop and it starts to snow. The snow gathers in a north
facing hollow. This is because the sun cannot melt it here.
Neve forms: The layers of snow build up and a neve is formed as the air is
squeezed out. As the air is squeezed out, the granules of snow crystalize and the
snow turns to ice. It also turns blue in colour.
During Glaciation
2. The ice moves downhill under the force of gravity. The glacier creates momentum
because ice over 30Km thick can flow in a plastic form due to changes in its internal
crystal structure. This allows the ice to change shape as it moves downhill.
3. The hollow has become much deeper, forming a nivation hollow due to the forces of
plucking and abrasion. A bergschrund forms – this is a large crevasse which
separates the flowing ice from the ice attached to the back wall.
4. Plucking creates a steep back wall. Plucking is when the ice freezes onto the rock
face and pulls large chunks of rock away, as the ice moves downhill. Abrasion
creates a deep smooth base. Abrasion is when rocks trapped between the ice and
the rock face scrape along the rock face, wearing away the rock. Abrasion is like
the action of sand paper.
5. Frost Shattering weathers the peak of the mountain, making it jagged. Rocks fall
off and are transported by the glacier. This aids abrasion. This is when water
enters the pores or cracks in a rock. Repeated heating and cooling creates a freeze
thaw action. This causes the crack in the rock to get bigger, until it eventually
breaks and shatters.
6. Friction causes the glacier to melt near the rock face, which lubricates the ice.
This helps rotational slip to move the glacier out of the hollow.
7. As the glacier moves out of the hollow, it loses energy and starts to deposit rocks
which it is carrying. These rocks build up to form the corrie lip.
After Glaciation
8. Temperatures rise and it the ice/snow begins to melt. Glaciers retreat. Glacial melt
water is often left in the corrie, which forms a lochan or a tarn.
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3. U-Shaped Valley, Hanging Valley, Misit Stream and Scree
U-Shaped Valley and hanging valleys are formed in a very similar way to the
formation of corries, arêtes and pyramidal peaks. Like the corrie, it takes place
over three stages.
Before Glaciation
1. Temperatures: begin to drop and it starts to snow. The snow gathers in a v-shaped
valley.
Neve forms: The layers of snow build up and a neve is formed as the air is
squeezed out. As the air is squeezed out, the granules of snow crystalize and the
snow turns to ice. It also turns blue in colour.
Interlocking Spurs: Interlocking spurs are present in the v-shaped valley where
the river was not powerful enough to erode through hard bands of rock.
During Glaciation
2. Bulldozing: The ice bulldozes through the valley making the sides steeper and the
valley deeper.
3. Plucking creates steepness. Plucking is when…
4. Abrasion creates deepness. Abrasion is when…
5. The glacier rocks back and forward to create friction, which acts as a lubricant.
The lubricant helps the glacier move through the valley.
6. Spurs: The glacier is so powerful that, unlike the river, it has the power to erode
the interlocking spurs. When this occurs, a truncated spur is created.
After Glaciation
7. Temperatures rise and the ice begins to melt.
8. Misfit Stream- where the glacial deposits build up to form moraine along the base
of the u-shaped valley, often a misfit stream will form in the depression between
moraines.
9. Ribbon Lake- where the glacial meltwater fills the valley often a ribbon lake is
formed.
10. Scree- scree is often formed on the steep slopes of the U-shaped valley. Scree is
when frost shattering attacks the cracks and weaknesses in the rock. The rock
fragments are made looser when the weaknesses are further attacked by wind and
rain. Scree is loose fragments of rock on the valley slopes.
Hanging Valley
Often in the tributary valley, a smaller glacier will form. The same processes take
place, but on a much smaller scale. The tributary valley is made wider and deeper, but
not as deep as the main valley. When the ice retreats
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4. Glacial Deposition – Moraines, Drumlins, Erratics
What is glacial deposition?
Glacial deposition is when the glacier loses energy and as a result, it starts to deposit
any rocks, fragments or debris it is carrying. Glacial Deposition takes place in two
forms:
a. Glacial Deposits- this is when the glacier drops debris that it is carrying as it
retreats. Glacial deposits (often called till) are unsorted mounds and are
described by geologists as unstratified.
b. Fluvio-glacial deposits- these are formed by the meltwater streams which are
formed as the glacier melts. The meltwater streams deposit the debris as they
move downstream. These types of deposits are sorted or stratified.
Terminal Moraine•
This is an unsorted crescent shaped mound of rocks and debris which mark the
furthest point the glacier travelled.
•
The snout of the glacier pushed rocks and gravels forward which remained in
the same place well after the glacier melted or retreated.
•
If more than one glacier has been present, but not travelled as far as the
original, a second form of terminal moraine is found called recessional moraine.
Ground Moraine
•
Often called Boulder Clay or Till
•
Material was transported by glacier and deposited when the ice retreated.
•
Ground Moraine is considerably deep
Lateral Moraine
•
Found at the side of where the glacier would have been
•
The debris from freeze-thaw (scree) is left
behind marking out how wide the glacier was.
Medial Moraine
This is when two glaciers converage, as do the lateral
moraines, which merge to form medial moraine. As
medial moraine is two moraines together it is often
thicker and deeper.
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Drumlins
Drumlins are: Drumlins are small hills formed by glacial deposition. Drumlins are
formed as a result of glacial deposits which mean that they are unsorted mounds of
glacial till.
Trigger: Drumlins are formed when the melting glacier stops moving due to a trigger
such as a rock, or slow melting chunk of ice in the ground. The glacier begins to melt
around the trigger and the materials build up to form the steep stoss of the drumlin.
Stoss and Lee: The stoss is made steeper by plucking, as the glaciers erosional powers
are still at work. The rest of the debris forms on the opposite side of the trigger,
forming the gentle lee slope. The lee is left facing the direction that the ice moved in.
Erratic
Erratic are large pieces of rock which are plucked by the glacier and transported down
the valley. Erratic are large pieces of rock found in low lying areas and are different to
the bed rock of the area they are found.
Kettle Hole
A kettle hole is a depression found in the ground,
filled with water.
As the glacier melts, chunks of ice often melt
slowly into the ground. As the fluvio-glacial
streams flow around the ice, they deposit
sediments.
The sediments build up to form an outwash plain.
The ice continues to slowly melt. Sediments then build up on top of the ice. Eventually,
the sediments collapse, fall into the depression and the kettle hole is formed.
If a kettle hole is deep enough to reach the water table, it forms a kettle lake.
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Land Use conflicts and Solutions : Glaciated Upland
There are a number of land use conflicts and matching solutions which take place in
glaciated upland areas like Loch Lomond and the villages which surround it. A summary
of what we have studied is listed below:
Conflict
Tourists leave farmers
gates open which allows
sheep to escape.
Tourists going for long
walks across farmers fields
can lead to footpath
erosion
Loch Lomond Is notorious
for illegal camping and
outdoor drinking which
upsets farm animals and
local people.
House Prices increase in
honeypot areas like Balloch
and Luss due to the demand
by tourists. Tourists also
buy up these houses for
holiday homes which leads
to the ghost town effect.
Many of the services in
the area are aimed only
at tourists. This means
that the price of goods in
shops often increase.
Ghost Town Effect- in low
season the honeypot tourist
areas are often left with
few tourists which can lead
to seasonal unemployment
in places like Luss
Tourists cause traffic
problems at peak times like
bank holidays and weekends.
They cause congestion on
the narrow A82 road,
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Solution
Step Stool fences or kissing gates which mean the
gates close automatically meaning sheep stay in the
field
Wooden planks or boards can be put down on popular
routes which save people walking on the grass.
Often, some footpaths are closed and people are
directed to other ones which allow the old ones to
regenerate.
Park Rangers are employed to educate people about
the countryside code and respecting the area.
National Park Police have the power to disperse
people which stops them from drinking outside
Camping is illegal in Loch Lomond, unless it is in a
designated approved camping area.
Local bylaws in some villages/areas often stop people
from buying up local properties unless they are born in
the area or have rented for a period of time.
Help to buy schemes introduced by the recent
government have offered a 20% equity loan to help
people onto the property ladder.
IN some areas, there is a postbus which delivers mail
but also picks up local people and takes them around
the area.
Large super markets are often given incentives to
develop in or around these areas to bring down the
price of commodities.
At loch Lomond, more activities have been introduced
in low season. For example, there is now a drive in
movie theatre at Halloween and Christmas.
Out of town car parks on the outskirts of villages
stops cars from entering the village making it less
congested.
There are extensive car parking facilities south of
Loch Lomond at Loch Lomond Shores.
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Lithosphere: Glaciation
around villages like Luss and
often park on grassy verges
if there are no other
parking spaces available.
HEP stations are deemed
as an eyesore due the
industrial looking pipes.
They are also noisy during
construction which detracts
from the peacefulness of
the area, sought by
tourists.
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Sustainable transport links have been developed
between Glasgow and Loch Lomond. There are regular
bus services and direct trains to Balloch Train
Stations.
Often, trees are planted around the pipes of the HEP
station which disguises the industrial looking pipes.
To minimise noise pollution, the HEP Stations are built
in low season when there are less tourists about.
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Lithosphere: Glaciation