AQA Geography - Glacial processes

Valley glacier
A glacier bounded by the walls of a valley, and descending from high mountains, from an ice cap on a plateau, or from an ice sheet.
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Ice cap
A dome-shaped mass of glacier ice, usually situated in a highland area, and generally defined as covering up to 50,000 square kilometres.
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Ice sheet
A mass of ice and snow of considerable thickness, defined as covering an area of more than 50,000 square kilometres.
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Piedmont glacier
A glacier that spreads out as a wide lobe as it leaves a narrow mountain valley to enter a wider valley or a plain.
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Cold-based (polar) glaciers
Cold-based (polar) glaciers occur in polar latitudes where the temperature of the snowfall is far below freezing and the glacier remains at well below freezing point
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Warm-based (temperate/ alpine) glaciers
Warm-based (temperate/ alpine) glaciers – water is present throughout the ice mass and acts as a lubricant
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How do Cold based glaciers occur?
when the bulk of the ice is below the pressure-melting point and therefore frozen to the bed rock Antarctica and Greenland, little ice movement occurs.
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How do warm based glaciers occur?
where ice is warmer at the base (at the pressure melting point), allowing meltwater to be present.  Alps, Alaska.
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How do cold based glaciers move?
Internal Deformation
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Internal Deformation
occurs when the weight of ice and gravity causes the ice crystals to deform.
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How do warm based glaciers move?
Basal Slippage
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Basal Slippage
is the act of a glacier sliding over the bed due to meltwater under the ice acting as a lubricant.
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what does the Rate of movement depends on?
Gravity – steeper the gradient, the greater the pull Friction – Less friction, more movement Meltwater – Lubrication of the ground allowing slip Ice temperature Ice mass – The heavier it is, the more energy it has to move
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Thermal Regime
This is the temperature profile of a glacier - basically the variation in temperature with depth
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Pressure Melting Point (PMP)
At ground pressure the melting point is 0oC Under pressure the melting point is lower, causing ice to melt below freezing
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Extensional flow
If ice flows over a steeper slope it will flow faster leading it to become thinner and fracturing. This leaves large gaps in the ice which are called crevasses
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Compressional flow
Ice flowing over a gentle slope causes the slowing of the ice, causing it to pile up and become thicker. Crevasses close.
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Geomorphological processes
are natural mechanisms of weathering, erosion and deposition that result in the modification of the surficial materials and landforms at the earth's surface
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name 4 Geomorphological processes
weathering Erosion Transportation Deposition
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examples of Weathering
frost action, nivation; ice movement: internal deformation, rotational, compressional, extensional & basal sliding
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examples of Erosion
plucking & abrasion
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Where does Rotational flow occur?
this occurs within the corrie (cirque).
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How does Rotational flow occur?
Ice moving downhill can pivot about a point, producing a rotational movement. This, combined with increased pressure within the rock hollow, leads to greater erosion and an over-deepening of the corrie floor
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The glacier uses this to adhere to part of the ground. Then, as the glacier forces the ice frozen to the ground to continue moving down slope, the rock may be pulled out of the ground and moved down slope as well.
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Once glaciers have rock and sediment at their bases they can push this sediment against the ground and use it like sandpaper. This abrasion of rock against rock can scour the landscape and leave large gouges, small striations, or even a finely polish
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3 types of glacial transportation of Weathered material
Supraglacial Englacial Subglacial
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where does deposition occur?
Usually occurs on the ablation zone, close the the glacial snout
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why is Melt water hugely important in the fluvioglacial processes?
It is also responsible for the landscapes, by allowing glaciers to move by basal slippage within Temperate or warm based glaciers.
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How can meltwater move through a glacier?
, water can move on the glaciers surface (supraglacial channels), within the ice (englacial channels) and under the ice (subglacially).
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How water that flows on the surface then enters and englacial channe
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Melt water streams
When glacial ice melts, water runs out as streams of meltwater Warm-based glaciers produce lots of meltwater
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How might discharge change during winter?
In winter, melt water discharge may even stop, as temperature may never rise above the pressure melting point.
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What is the differences between meltwater and regular streams?
Meltwater streams cause erosion in the same way as normal rivers – but they cause more erosion than rivers the same size
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Why does this differences occur?
The confinement of the ice means they flow quickly under pressure, so they can carry lots of material which can erode the landscape
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meltwater channels
wide and deep streams that form deep troughs in the landscape
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what are the 4 Erosional processes
Hydraulic Action Corrasion/ Abrasion Corrosion/ Solution Attrition
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Hydraulic Action
where the sheer force of the water erodes the stones, bed and banks of the meltwater channel
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Corrasion/ Abrasion
where stones in transport are thrown into the bed and the banks eroding them
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Corrosion/ Solution
where weak acids within the water react with the rocks and bed and bank of the meltwater channel
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where stones in transport are thrown into one another
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What is the meltwater water like?
Flows under considerable pressure, High velocity and Very turbulent
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what are the 4 Transportational Processes
Solution Suspension Saltation Traction
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- minerals are dissolved in the water and carried along in solution
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- fine light material is carried along in the water.
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- small pebbles and stones are bounced along the channel.
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- large boulders and rocks are rolled along the channel.
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why and how does deposition occur?
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.
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How is deposition found?
Deposits may be found in layers (stratified) as a result of seasonal variations in meltwater flow.
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what are The main features produced by fluvioglacial deposition?
The main features produced by fluvioglacial deposition are eskers, kames and the outwash plain.
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what are periglacial environments?
Areas that experience a cold climate, with intense frost action and the development of permafrost- tundra areas
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where are periglacial envronments found?
areas such as the tundra of northern Russia, Alska and Canada, together with a high mountainouos area such as the Alp, experience a periglacial climate.
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climate of periglacial envronments
climate of periglacial regions is marked persistently low temperatures. Summers are short but temperatures can sometimes reach about 15 degrees celcius. In winter, the temperatures remain well below zero and in some areas many fall below -50 at times
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Where subsoil temperatures remain below zero for atleast two consecutive years permafrost will occur.
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what are the three types of perma frost?
Continuous, Discontinuous and sporadic
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what is the difference between Discontinuous and sporadic
Discontinuous – found in slightly warmer regions where freezing conditions do not penetrate great depths. Sporadic – mean annual temperatures are around or just below freezing, so permafrost appears only in isolated spots
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why does discontinuous occur?
Discontinuous due to breaks around rivers, lakes and the sea. Patches are frozen
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freeze thaw action
this process has already been descibed in detail on,previous card. In periglacial areas, screes develop at the foot of slopes as a result of frost shattering. On relatively flat areas, extensive spreads od angular boulders are left
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when the active layer thaws in the summer, excessive lubrication reduces the friction between soil particles. Even on slopes as shallow as 2 degrees, parts of the active layer begin to move downslope. This leads to solifluction sheets or lobes
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Frost heave
as the active layer starts to refreeze, ice cyrstals begin to develop. They increase the volume of the soil and cause an upward expansion of the soil surface. Frost heave is most significant in fine-grained material, and as it is uneven, it formsdome
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Pingos are hills with an ice core. They are between 3 to 70 metres in height and have a diameter between 30 to 1000 metres.
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is an irregular land surface consisting of hills and hollows formed when permafrost thaws.
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Terracettes are a series of small ridges in the ground, underneath vegetation, on a sloped piece of land. They are formed when the active layer thaws and gravity allows material to slump down underneath the vegetation.
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Blockfields are extensive areas of angular rock that have been created by regular freeze-thaw activity fragmenting exposed rock in situ. The material is left strewn across the level ground
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Ice wedges
are vertical masses of ice that penetrate down to 10 metres from the surface in some cases. They are formed as a result of the large amount of ground ice present and following significant temperature fluctuations
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Other cards in this set

Card 2


Ice cap


A dome-shaped mass of glacier ice, usually situated in a highland area, and generally defined as covering up to 50,000 square kilometres.

Card 3


Ice sheet


Preview of the front of card 3

Card 4


Piedmont glacier


Preview of the front of card 4

Card 5


Cold-based (polar) glaciers


Preview of the front of card 5
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