Glaciated landscapes Flashcards
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What is a glacier?
Moving body of ice
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How far do some glaciers move per day?
Up to 25cm per day
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Why do glaciers move?
Gravity forcing them down
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Why are glaciers important and how many people rely on them?
Drinking water, crop irrigation, tourism, recreation and hydroelectricity
1/3 of the world’s population rely on glaciers
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What is happening to many glaciers around the world?
What does this cause?
Many glaciers around the world are melting (negative mass balance).
This is causing sea levels to rise 2.6m in the last 60 years, causing extinction of animals, loss of resources, ecosystems and habitats
UNIT 1
Where are glaciers found
High latitude (poles) and altitude (mountainous) locations, where the temperature is regularly below 0 degrees Celsius (Cryosphere)
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Examples of accumulation (inputs) of snow.
Wind blown snow, Precipitation, desublimation (condensation into ice), avalanche debris.
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Examples of ablation (outputs) of snow
Meltwater, Calving (breakaway of ice), Rock debris, wind-blown snow, avalanche debris, solar energy, sublimation (evaporation from ice).
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Where does accumulation occur?
Where does ablation occur?
What is the line of equilibrium?
accumulation at head
ablation at toe
line of equilibrium is where inputs = outputs
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Describe the formation of glaciers
Snow falls, which contains ait, more snow falls, compacting the pre existing snow. Snow that survives one winters freezing and one summers thawing is called firn. In summer meltwater percolates into the firn, in winter it refreezes, causing it to become denser. After several years and a depth of 20m, there is very little air left and glacial ice is formed.
UNIT 1
What is mass balance?
Positive?
Negative?
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Mass balance is the growth or retreat of a glacier
Positive - growth
negative - retreat
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Draw a Glacier flow diagram
:)
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What is till?
Unsorted material deposited directly by glacial ice
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What is a moraine?
Deposited sediment from a retreating glacier
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Moraines formation
Till is deposited by glacier, debris dropped on top of glacier and material eroded from plucking.
Retreating glacier causes sediment to be deposited, causing a recessional moraine to form
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Glacier advance and retreat
Positive mass balance means glacier advances, becoming thicker and ploughs over moraines.
Negative mass balance means glacier retreats, but is still flowing forward due to gravity, causing the glacier to become thinner.
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Mass balance graph and description:
In winter there is lots of accumulation, in spring and autumn there is equal amounts of accumulation and ablation in summer there is more ablation then accumulation.
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What percentage of glaciers currently have a negative mass balance
75%
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How much of the earth’s surface is covered by glaciers?
10%
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How much of the world’s freshwater is stored in glaciers?
75%
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What is a ice period
permanent ice at the poles
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What is an interglacial period?
Periods of warm, causing glaciers to have a negative mass balance
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What is a Glacial period?
Period of cold, causing glaciers to have positive mass balance.
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When was the Holocene period
Interglacial or Glacial?
11,500 ybp to present
Interglacial
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When was the Devensian period?
Interglacial or Glacial?
80,000 ybp to 11,500 ybp
Glacial
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When was the Ipswichian period?
Interglacial or Glacial?
80,00 ybp to 100,000 ybp
Interglacial
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When was the Wolstonian period?
Interglacial or Glacial?
100,000 ybp to 140,000 ybp
Glacial
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When was the Hoxian period?
Interglacial or Glacial?
140,000 ybp to 200,000ybp
Interglacial
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Why do cycles of Interglacial or Glacial periods exist?
Changes in long-term cyclical change, due to changes in Earth’s orbits around to sun, leading to a variation of insolation received by the earth, caused mostly by Milankovitch cycles.
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What is the current tilt of the axis of the earth?
23.5 degrees
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Perihelion meaning.
Aphelion meaning.
Closest point to the sun
Furthest point from the sun
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Winter solstice
Summer solstice
Equinox
Shortest day
Longest day
Equal insolation of both hemisphere
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What are Milankovitch cycles?
How much of they impact the amount of incoming insolation
Orbital variations.
Causing up to 25% variation
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Stretch (eccentricity) of the orbit description
Impacts
Time frame
Impact of orbital shape (more oval vs more circular). At most elliptical there is 23% more insolation then at furthest point. Every 100,000 years
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Axis tilt (Obliquity).
Impacts
Time frame
Tilt of the earth, varies between 22.1 and 24.5 degrees. Tilted towards the sun causes warmer climates, vice versa.
Over 41,000 years
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Wobble (precession)
Impacts
Time frame
earth wobbles in orbit due to the relationship between the sun and moon (Tidal forces). Causes variations in temperatures. Takes 25,771.5 years
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What is long term climate change caused by?
Milankovitch cycles
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What is responsible for glacial and interglacial periods?
Milankovitch cycles
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What is positive feedback in relation to glacial budget
Positive feedback amplifies changes in a glacial budget. Cooling leads to further cooling, warming leads to more warming
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What is surface albedo?
Earth’s reflectivity
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Why is it important to have high surface albedo?
More reflective surfaces, so more insolation is reflected back into space, causing decrease in temperature.
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What happens when there is low surface albedo?
Ice has melted, so there are less reflective areas, Insolation is absorbed into water, causing the temperature to increase
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How much insolation is reflected and absorbed by ice and snow (high albedo)
90% reflected to space
10% absorbed
(lower temperatures)
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How much insolation is absorbed/reflected with water (low albedo)
6% reflected
94% absorbed
(temperatures increase)
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Positive feedback relationship in with positive mass balance
Cooling of climate, Artic sea water freezes (ice cover increases), Darker surfaces hidden, increased albedo, decreased absorption of insolation…
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Positive feedback in relationship with negative mass balance
Increases in temperature, Artic sea ice melts, darker surfaces revealed, Albedo reduced, Increased absorption of solar radiation.
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Why is it hard to undo glacial melting
Warming leads to more warming due to positive feedback loops.
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Negative feedback in relation to glacial budget
Negative feedback reduces changes in a glacial budget. Warming leads to cooling
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Give an example of negative feedback in relation to glacial budget
Younger Dryas, due to thermohaline
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What is the thermohaline ocean circulation
Brings warm salty water to northwest Europe, causing warm winter conditions.
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What happens to cold water vs hot water
Cold water sinks
Hot water rises
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What is the Younger Dryas period
Towards the end of the last glacial period (Devensian) when temperatures were rising, the disruption to this ocean current in the North Atlantic led to a rapid period of cooling known as the Younger Dryas.
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When did the Younger Dryas occur?
13.25 thousand ybp to 11.25 thousand ybp
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How long did Younger Dryas period last
2 thousand years
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What was the drop of temperature in Greenland during the Younger Dryas?
-35 to -50 degrees celcius
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What was the change of ice accumulation in the Younger Dryas period
0.25 -> 0.32
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Explain how thermohaline currents caused the Younger Dryas period
Northern regions heated by the oceans. Ocean circulation is driven by Coldwater sinking in the North Atlantic. 12,800 years ago, freshwater made surface water less dense, keeping it from sinking. Air became colder for more then 100 years due to lack of northward transport of warm water. Northern Hemisphere has conditions like the last ice age. Rewarming occurred 11,600 years ago, within less then a decade ocean circulation was restored.
https://www.youtube.com/watch?v=kqWIwp1beIw
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Give 3 short term causes of climate change
Solar forcing (sunspots (increased solar outputs), Volcanic eruptions, Anthropogenic (human) factors.
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What is solar forcing?
Energy released by sun
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What is solar output linked to?
Sun spot activity
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How often do sunspots fluctuate?
On an 11 year cycle
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What was the little ice age caused by?
Low level of solar outputs
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When was the little iceage?
1645-1715
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What happened during the little ice age?
Sea ice expanded into Atlantic, Iceland and Greenland were impossible to ship too.
Baltic sea, rivers in the UK (like the Thames) froze over.
Permanent snow in Scotland covered Cairngorm mountains.
Glacier advanced in the Alps and threatened nearby towns
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Why do volcanic eruptions impact glaciers
Volcanoes release sulphur dioxide and ash into stratosphere, these reflect income solar radiation, leading to a decrease in temperature.
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Give three examples of Volcanoes that have impacted on climate change
Laki, Iceland, 1783, Europe was 3 degrees Celsius lower.
Tambora, Sumbawa Island, 1815, reduced temperatures by 0.7 degrees Celsius for 3 years
Mount Pinatubo, 1991, decreased temperatures by 0.4 degrees Celsius.
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What is Anthropogenic factors of short term climate change
Human activity linked to combustion of fossil fuels, releasing greenhouse gasses, causing enhanced greenhouse effect.
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How much has temperatures increased by due to anthropogenic factors
1.2 degrees Celsius since 1880
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How much of the Himalayas glaciers are in retreat?
95%
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How far were glaciers in the Himalayas retreating?
10-60m a year. Many small valley glaciers retreat 1km since the little ice age. Small glaciers have already dissapeared
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How much higher are temperature in the Himalayas? What effect is this having?
+ 1.6 degrees overall. Decreasing amounts of snowfall
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What percentage of glacier mass in the Himalayas are at risk?
1/4 of glacial mass could disappear by 2050
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How far has the Chota Shigiri Glacier in the Himalayas retreated?
950m from 1962 to 2008
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Where is the Glacier National Park USA
Montana
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By what year will the Glacier National park be glacier free?
2030
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How many Glaciers have disappeared in the Glacier national park since 1850?
In 1850 there were 150, in 2010 there was 25
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Why do New Zealand have areas of glacial growth?
Westerly atmospheric circulation, causing increased snowfall. Causing positive mass balance
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Why do areas in New Zealand have zero ice mass balance?
Equal amounts of loss and gain of ice
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Why are some areas in New Zealand glacial retreats
Glacial lakes have begun to grow at snouts. Causing calving away from the glacier into icebergs. Glaciers with lakes attached have lost 10% of mass over 30 years.
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What was ice extent like during the Devensian? What else did this impact upon?
Ice reached much further south, covering parts of the UK. Sea ice reached Iceland and Greenland. Due to this coastlines were much bigger as there were lower sea levels
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Why are Glaciers found at high latitudes?
Axis tilt of earth means they get less sunlight, meaning snow can fall consistently and meltwater will refreeze
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Why are glaciers found at high altitudes?
Low pressure, cool air (due to work done to rise), causing snowfall
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What is the cryosphere?
Parts of the crust and atmosphere that are below zero degrees for a part of the year
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How are icebergs formed
Broken of of glaciers into water via calving
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What is permafrost
permanently frozen ground
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What is the morphology of glaciers?
Form, shape and structure of ice
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What two factors impact the morphology of a glacier?
Climate and topography of land
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What is climate? And how does it impact a glacier’s morphology
Climate is contorlled by annual temperature cycle. Warmer climate causes negative mass balance vice versa.
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What is topography? And how does it impact glaciers morphology?
Topography is the natural shape of the land. Land surface, e.g. altitude. Controls physical dimensions of the glaciers and how they can flow.
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What is an unconstrained land mass?
morphology and flow pattern that is not fully dependent of the topography of land
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What is a constrained ice mass?
Morphology and flow pattern that is strongly based on topography
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Ice sheet:
Description, size, constrained or unconstrained?
Example
Topography is submerged in ice, forms gently sloping domes of ice several km thick. +50,000km2. Unconstrained. Antarctic ice sheet
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Ice cap:
Description, size, constrained or unconstrained?
Example
Smaller version of an ice sheet. >50,000km2. Unconstrained. Vatnajökull ice sheet
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Ice field:
Description, size, constrained or unconstrained?
Example
Ice covering upland area, does not bury topography. 10-10,000km2. Constrained. Patagonian ice fields
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Valley glacier:
Description, size, constrained or unconstrained?
Example
Confined between valley walls, finishing in a narrow tongue, made from ice caps, sheets or cirques. 3-1500km2. Constrained, Aletsch glacier, Swiss Alps
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Piedmont glacier:
Description, size, constrained or unconstrained?
Example
Valley Glacier that extends beyond end of a mountain into flat area, spreading out. 3-1000km2. Constrained. Malaspina, Alaska
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Cirque glacier:
Description, size, constrained or unconstrained?
Example
Occupies a hollow on a mountain side, calves out a corrie. 0.5-0.8 km2. Constrained. Styggebrean Norway
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Ice shelf/sea ice:
Description, size, constrained or unconstrained?
Example
Large area of floating glacier ice, many glaciers coalesce (fuse). 10-10,000km2. unconstrained. Larsen Ice shelf
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What is thermal regime?
the temperature of the ice
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What are the two types of thermal regimes, and what is the difference?
Cold based (polar glaciers) - Glacier is permanently frozen to ground. Average temperature is well bellow 0, surface temperature is -20 to -30. High latitudes.
Warm based (temperate glaciers) - Glacier is not frozen to bedrock. Temperature fluctuates to above melting point, causing meltwater, this is due to the pressure melting point (water melts due to high pressure, even while temperature is below 0 degrees celcius). High altitudes.
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Why are glaciers able to move?
Glacial ice can deform
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What is pressure melting?
Ice melts at temperature below 0 degrees, due to pressure of overlying ice.
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What is the equation for pressure melting?
melting point falls at a rate of 1 degree Celsius for every 100kg/cm3 of pressure
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In what thermal regime do glaciers melt. Why?
Warm based glaciers reach pressure melting point at depth. Causing meltwater.
Cold based glaciers do not melt as temperature is far from pressure melting point all thought the glacier.
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What is Regelation
Ice melts under pressure, when pressure is relieved water refreezes
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Is Basal sliding warm based or cold based?
Warm
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What is Basal sliding? This is not a specific type of movement, all warm based glaciers do this.
Only occurs when there is meltwater, acting as a lubricant reducing friction, enabling movement.
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What is enhanced Basal creep? Cold or warm?
Glacier comes into contact with an obstacle. Ice deforms around obstacle, but does NOT reach pressure melting point. Warm based only.
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What is the Stoss and Lee side?
Stoss - up side
Lee - down side
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What is Regelation slip. Cold or warm?
f temperature of ice is close to pressure melting point, increased pressure from the stoss side (up movement) of glacier will induce melting. Glacier is able to slip and meltwater flows around obstacle to the Lee side, pressure is reduced and meltwater refreezes - linking to regulation. Warm only.
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What is internal deformation. This is not a specific type of movement, all warm and cold based glaciers do this.
individual grains of ice withing glacier responding to pressure, this is NOT melting. This is effected with ice thickness and slope angle.
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What is intergranular flow? Warm or cold based?
Displacement of ice grains relative to one another. Bottom grains are stationary while top rotate clockwise, this is due to slope angle as it is reliant on gravity. A steeper slope angle causes more movement. Warm and cold based.
UNIT 2
What is Laminar flow? Warm or cold based?
Layers of ice slipping over one another. Ice at the bottom has slower relative velocity then ice at top. This is due to slope angle as it is reliant of gravity. A steeper slope angle causes more movement. Warm and cold based.
UNIT 2
What is the deformation of ice called? What is it caused by? Warm or cold?
Ice creep. Caused by increased ice thick and/or slope angle. Warm and cold
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How does ice deformation cause ice faults, fractures and crevasses.
Ice is not able to deform quick enough
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Explain extensional and compressing flow.
When slope gradient is increased, ice accelerated, causing crevasses. This is extensional flow.
When slope gradient is decreased, ice slows down, causing ice behind to catch up, leading to ice thickening, and crevasses to close. This is compressing flow.
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What is subglacial bed deformation? Warm or cold based? What does this cause?
Glacier moves over weak, loose rock, causing sediment to deform under weight of glacier. Warm based glacier only.
In Icelandic glaciers this causes 90% of glacial movement
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What thermal regime glaciers move faster?
Warm
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What is the range of movement in a glacier per year?
3-300m per year
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How does slope angle impact velocity?
Higher slope angle = more velocity
vice versa
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How does thermal regime impact velocity?
Warm based glaciers have more velocity due to
- Water acting as lubricant
- More movement options
- Basal sliding
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What are glacial surges?
Periods of rapid movements
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How much faster can a glacier move in surge conditions?
Up to 1000 times faster
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What are glacial surges caused by?
change of flow pattern of subglacial meltwater
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Describe surge conditions
Water builds underneath glaciers. Increase of ice in accumulation zone. During winter subglacial meltwater channels are closed, increasing accumulation of ice. During summer ice accumulation is so great that subglacial meltwater channels do not open. Pressure melting point and subglacial meltwater separates basal ice from it’s bed, lubricating it and causing faster velocity. Abundant water increased pore water pressure, adding to movement, Surge occurs and glacier returns to normal flow.
UNIT 2
What case study is used for glacial surges
Muldrow Glacier, 2021
UNIT 2
When did Muldrow Glacier last surge? How far did it move?
1956, moving 4 miles
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How far did Muldrow Glacier move? How much more is this then normal? What did this cause?
200ft in 4 days, 10-20m in one day, 100x faster then normal, caused massive crevasses
UNIT 2
Where does Muldrow lie that impacts surge conditions
Lies on a fault line, which causes earthquakes
UNIT 3
What is weathering?
Breakdown of rock, in situ
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What are the two processes of weathering
Physical processes and chemical processes
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What is erosion
Removal of rock by ice, water, wind or gravity
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What are two types of weathering?
Freeze thaw / frost shattering, dilatation
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Explain freeze thaw weathering
Water enters a crack in a rock, the temperature fluctuates on either side of 0 degrees Celsius. Water freezes and expands by 9% in volume. Putting pressure on rock, after repeated cycles the rock splits
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What impacts freeze thaw weathering?
Geology of rock (more porous (absorption)/ bedding (gaps in formation)
Climate - temperature must be able to fluctuate between 0 degrees Celsius
Altitude - decrease in temp higher up
Aspect - Orientation of rock, North vs Southern hemisphere
UNIT 3
What is an example of freeze thaw?
Summit of Glyder Fawr
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Explain dilatation
Rocks fracture parralell to pressure when the pressure is released (glacier melts). Rocks expand and fracture fue to the pressure release. Called pressure relase or unloading.
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What are three erosional processes?
Abrasion, Plucking, Sub-glacial meltwater erosion.
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Explain abrasion
Weathered rocks are embedded as sub glacial debris (under glacier), this scrapes away at rock. Large pieces of rock cause scratches and striations, while fine particles cause smoothing an polishing (like sandpaper). When the debris gets worn away it turns into rock flour.
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What are the factors effecting abrasion?
Ice thickness - thicker ice causes more erosion due to higher pressure, but too thick and the glacier becomes hard to move
Subglacial meltwater - Increases speed of glacier, but too much lubricant means the glacier will not erode
Relative hardness/resistance of debris and bedrock - if bedrock is harder there will be less erosion, weak debris turns into rock flour
Shape of debris - angular debris causes striations and cracks, fine sand and clay smooth and polish
Supply of debris - More debris causes more erosion, but it depends on the type of debris. Too much causes lower speed
Speed of glacier - Fast movement causes more erosion up to a point - too fast causes less erosion
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Explain plucking
meltwater seeps into cracks in the rock, it refreezes, when the glacier moves to rock is plucked from the bedrock, causing the entrapment of rocks
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What does plucking need to occour?
fractures in bedrock, resistant obstacles and meltwater
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Plucking also occurs in what movement?
Regelation slip
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What is sub glacier meltwater erosion?
Meltwater channels under glacier, high velocity causes erosion at the glacier’s bed and the widening and deepening of channels
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What is an example of sub-glacial meltwater erosion?
Gwaun valley, North Pembrokeshire (South Wales)
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How does sub-glacial meltwater occour?
Increase of meltwater in summer, water flows into cracks and forces rocks out (hydraulic action).
Rocks grind and scrape rock (abrasion)
Ricks bounce around, making them rounder (attrition)
Chemicals in rock release minerals (corrosion)
Lateral erosion and vertical erosion find path of least resistance
UNIT 3
Why are sub-glacial meltwater channels powerful?
Ice adds pressure, increasing hydrostatic pressure and velocity
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Why do sub-glacial meltwater channels have different discharge patterns to normal streams?
discharge comes from ablation in winter, movement is based on topography and movement of ice
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What is a Macro landform?
What is a meso landform
What is a micro landform
Macro - big 1km+
Meso are often found in macro landforms
Micro are the smallest and often a few m
UNIT 3
What is a cirque/cwm/corrie
Macro/Meso/Micro?
Case study
A large bowl shaped hollow, found at the head of a valley glacier.
Macro
Cwm coch
UNIT 3
How many cirques surround the Nant Ffrancon valley? What direction do they face?
7, North east
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How are cirques/cwm/corrie formed
on North facing slopes in winter, small hollows freeze thaw weathering occurs. in summer meltwater removes the debris, enlarging the hollow, called nivation. Firn compacts into ice.
Accumulation results in rotational movement of ice, meltwater from pressure melting adds to this effects, this movement causes stage 2.
Ice rotates, removing fragments from the back wall via plucking, causing a steep, jagged backwall. Rock fragments cause ablation on the hollows floor, deepening the corrie. Crevasses, called bergschrunds add meltwater, causing more rotational movement. Pressure release causes dilation cracks to form, weakening the floor of the glacier, aiding erosion. Glacier begins to moves over the lip of the corrie and out of the rock basin. with abrasion on the stoss side and plucking on the lee side.
UNIT 3
What orientations are cirques. Why?
Northern hemisphere corries face north east. Receives the least amount of insolation (lower temperatures), meaning firn can form
UNIT 3
What is a rose diagram?
Circular histogram, showing directional data and frequency
UNIT 3
What is a Arete? How are they formed?
Macro/Meso/Micro?
Case study
Sharp, knife edge ridge, produced by two corries eroding back to back towards each over (or two glacial troughs).
Macro
Crib Goch - Snowdonia
UNIT 3
What does the Gribin Ridge (Arete) separate
Two cirques, cwm cneifion and cwm bochlwyd
UNIT 3
What is a Pyramidal Peak? How are they formed?
Macro/Meso/Micro?
Case study
Three or more corries erode, the remaining central area becomes sharp and steeper due to frost shattering.
Macro
Glyder Fawr - Snowdonia
UNIT 3
How tall is Glyder Fawr? What type of weathering occurs at the top because of its height?
1001m, freeze thaw weathering
UNIT 3
What is a Glacial Trough? How are they formed?
Macro/Meso/Micro?
Case study
A U shaped valley, formed when glaciers flow into a pre-existing v shaped river valley. Home to a misfit river
Macro
Nant ffrancon Valley
UNIT 3
How long and deep is Nant Ffrancon Valley
700m deep and 5km long
UNIT 3
What is a Truncated spur? How are they formed?
Macro/Meso/Micro?
Case study
steep cliff face in a glacial trough. In a pre existing river valley interlocking spurs occour, as the river erodes the path of least resistance. As the glaicer moves dont the valley these interlocking spurs are eroded.
UNIT 3
What landforms also occour in Nant Ffrancon valley?
Roche Mountonees, truncated spurs, hanging valleys and misfit river (Afon Ogwen)
UNIT 3
What is a Hanging valley? How are they formed?
Macro/Meso/Micro?
Case study
A smaller U shaped valley joins a larger glacier. because the small glacier erodes less vertically it is hanging above the larger glacier. May have waterfalls.
Macro
UNIT 3
What is a Ribbon lakes? How are they formed?
Macro/Meso/Micro?
Case study
Long, narrow lake found in glacial troughs. Glacier moves over alternating band of hard and soft rock. The glacier erodes the softer rock more then the hard rock. The outcrops of hard rock are called rock bars/steps. rainwater accumulates, creating a lake.
Macro
Llyn Ogwen - ribbon lake
Ogwen step - rock step
UNIT 3
How is a rock step formed?
Case Study
a change in geology, band of hard rock and band of soft rock. Glacier does not erode hard rock but erodes soft rock, causing a drop in altitude.
Ogwen step
UNIT 3
How much of a drop is Ogwen step?
170m
UNIT 3
How long and wide is Llyn Ogwen? How was it formed?
1..5km long and 350m wide. Formed by Ogwen glacier
UNIT 3
What is a Roche Moutonnees? How are they formed?
Macro/Meso/Micro?
Case study
Resistant rock that is smooth on one side and rigid on the other. Formed during regulation slip, with abrasion on the stoss side and plucking on the lee side.
Meso
Pen y Benglog - on Ogwen step
UNIT 3
What is a Crag and tail? How are they formed?
Macro/Meso/Micro?
Case study
An steep wall of rock followed by a gentle slope. Resistant rock protects softer rock behind it, forming a gently sloping tail on lee side and a steep side, which has plucking and abrasion occur.
Meso
Edinburgh castle
UNIT 3
How tall is the Edinburgh Crag and Tail? What type of rock was it made from?
130m tall. Igneous rock
UNIT 3
What is a Striations? How are they formed?
Macro/Meso/Micro?
Case study
long scratches on bedrock, from abrasion
micro
Found on Roche Mountonees in Nant Ffrancon valley
UNIT 3
What is a Chatter marks? How are they formed?
Macro/Meso/Micro?
Case study
small intermittent chips from abrasion, ice is not in continuous contact with rock.
Micro
Found on Roche Mountonees in Nant Ffrancon valley
UNIT 3
What is a polished rock? How are they formed?
Macro/Meso/Micro?
Case study
sand, silt and clay (fine particles) polish rock surface, from abrasion.
Micro
Found on Roche Mountonees in Nant Ffrancon valley
UNIT 4
What is fluvial glacial transport?
Transport of debris by meltwater
UNIT 4
What does entrained rock debris mean?
Rock debris inside the glacier
UNIT 4
What are the four locations of debris
Surface (supraglacial) , Within (englacial), Base (subglacial), Front (proglacial)
UNIT 4
What is an erratic?
Different rock types to the bedrock
UNIT 4
What is an example of an erratic?
Canadian Rockies, transported over 300km and weigh over 16 000 tones
UNIT 4
How can debris mover from one area to another. What does some of this this depend on?
Supra -> englacial, snow covers supra debris, making it englacial, this causes layers of debris and ice
Englacial -> Supra, glacier melts top layer
Depending on the topography of the ground,
extensional flow, causes debris to flow into crevasses, becoming englacial
compressional flow, sub or englacial material is moved towards the surface (supra)
UNIT 4
What landforms are deposited by glacial ice, where are these found?
Drumlins, Terminal moraines, recessional moraines, Lateral moraines, medial moraines, push moraines.
These are found in the till planes
UNIT 4
What landforms are deposited by meltwater (fluvioglacial), Where are these found? Why?
Eskers, Kames, Kame terraces, Kettle Holes, Kettle Lakes, Varves. These are found in sandurs, or outwash plains, because the glacier has never reached
UNIT 4
What is glacial deposition called?
Glacial till
UNIT 4
What is Lodgement till?
What is lodgement till composed of?
How is till orientated?
Till that is plastered into the surface.
Rounded, compacted boulders, matrix of sand, mud and clay.
Orientated facing in one direction, the long axis shows direction of moment (aligned with the ice flow)
UNIT 4
What is an example of lodgement till?
Aberogwen
UNIT 4
What is Ablation till?
What is it composed of?
Where is this usually found?
Material is deposited due to ablation.
Composed of compacted, unsorted, unstratified material, meltwater removes finer (clay particles)
Found at the snout, ablation occurs, so glacier drops all the sediment, like a conveyer belt
UNIT 4
What is deformation till?
Wat is it composed of?
How is it formed/
sediment if folded, into well compacted shapes, composed of man materials.
Formed when a glacier re advances over a previously deposited till
UNIT 4
What is a moraine?
Accumulation of debris, left behind by a glacier after it retreats.
UNIT 4
What is a till plain?
Size?
Example
Flat area, formed by a glacial moraine, up to 50m thick.
East Anglia
UNIT 4
What is a drumlin?
Where/how is it formed?
How can the direction of glacial ice be seen?
Why may it be hard to distinguish drumlins, what is multiple drumlins called?
Elongated hill, streamlined tail.
Formed sub glacially
Fluvial theory - Formed from subglacial meltwater flooding, deposits are then streamlined by glacial ice
Deformational theory - (accepted), glacier moves over an obstacle, till is plastered around it, becoming streamlined
Movement is seen by the direction of the long axis
Vegetation has grown over drumlins, making them harder to see
UNIT 4
What is an Example of a Drumlin?
Found throughout Conwy valley
UNIT 4
What is a lateral moraine?
What margin is it?
How is it formed?
Moraine that forms on the edge of a glacier
Ice-Marginal Landform
Rocks from freeze thaw weathering on rocks above the glacier fall on the sides of the glacier, or debris is wind blown.
UNIT 4
What is a medial moraine?
What margin is it?
How is it formed?
Can it be seen after glacier retreat?
Moraine that form in the middle of a glacier
Ice marginal landform
Two valley glaciers meet (confluence). Two lateral moraines merge.
Cannot be seen after glacier melts?
UNIT 4
What is a terminal moraine?
How is it formed?
Moraine that marks the furthest advance of a glacier. (Snout)
Glacier has a negative mass balance, so is retreating, causing the deposition of debris and boulders. After the glacier has fully retreated a terminal, crescent shaped moraine is left
UNIT 4
What can terminal moraines act as for meltwater?
Act as a dam for proglacial lakes
UNIT 4
What is a recessional Moraine?
How is it formed?
Where are they found?
Representation of where a glacier has paused for a time during retreat.
Formed in the same way as terminal
Found behind the terminal moraine, in bands
UNIT 4
What is a push moraine?
What is the orientation of clasts, due to the formation
Glacier advances over existing moraine.
Clasts orientate themselves vertically
Not permanent
UNIT 4
Why is glacial debris more angular when transported englacial then subglacial?
Englacial - few changes, position is fixed
Subglacial - Abrasion occurs, forming rock flour.
UNIT 4
How can fluvioglacial material be transported?
What is this called when in the glacier? What is it called when it is deposited beyond the snout?
Transported, sub, en, supra glacial
Called ice-contact fluvioglacial deposits…..proglacial deposits
UNIT 4
Compare glacial and fluvioglacial deposits:
Glacial -
Poorly sorted
Unstratified
Angular (freeze thaw)
Fluvioglacial -
Well sorted
stratified
Rounded - eroded by water
UNIT 4
What is …… when referring to deposits
Sorting
Stratification
Shape
Arrangement of clasts (rock fragments) into similar sizes
Layering of similar sized clasts
Degree of roundness of clasts, (as a result of attrition) (Powers Index of roundness)
UNIT 4
What is an Esker?
Fluvioglacial or Glacial?
Subglacial or Supraglacial?
How are they formed?
What is Imbrication?
Long winding ridges of debris.
Fluvioglacial
Sub/en glacial
Running water with a high velocity (due to hydrostatic pressure)transports sediment. Fluctuating velocities due to seasonal variations allow for deposition, (tunnel may become blocked, stopping the flow of water, allowing for rapid deposition) A retreating glacier exposes the esker.
Imbrication - class align themselves in direction of flowing water
UNIT 4
What is an example of an Esker?
Pentir Esker, 400m long, 5-10m high
UNIT 4
What is a Kame + Kame Terrace?
Fluvioglacial or Glacial?
Subglacial or supra glacial?
Zone?
How are they formed
Why is debris angular?
Mounds of sediment
Supraglacial
Fluvioglacial
Ablation zone
Surface meltwater (supraglacial) streams pick up sediment, and flow into lake depressions on the surface of the ice, dropping the sediment and filling the depressions.
If the lake is at the glacier edge, a kame terrace will form, whereas a kame will form if away from edge
When the ice melts material is deposited on the valley floor
Debris is angular because they come straight from freeze thaw, then transported into lakes, with little abrasion
UNIT 4
What is an example of a Kame?
Pentir Kame
UNIT 4
What is a kettle hole (lake)?
Zone?
How are they formed
What are many kettle hole lakes filled with?
Depressions in the outwash plain.
Fluvioglacial
Dead ice calve from the snout of thee glacier. Deposition occurs, covering the dead ice, Ice melts, creating depressions.
Water may fill these holes, if the water table is high, or there is lots of rainfall with impermeable rock.
Water loving plants (hydrophytic)
UNIT 4
What is an example of a Kettle Hole?
Caernarfon and Pentir.
Pentir - 75m diameter, filled with hydrophytic plants
UNIT 4
What is a Proglacial lake?
Fluvioglacial or Glacial?
Zone?
Lakes in the depressions front of the glacier, or where recessional moraines act as a dam.
Fluvioglacial
Proglacial
UNIT 4
What is a Varve?
How are they formed
Alternating annual layers of fine silt/clay and coarser sand/gravels
During summer ablation occurs, so excess meltwater has a high velocity, allowing heavier sediments to be transported and deposited.
During Winter months meltwater has less velocity so fine particles and particles in suspension are dropped
UNIT 4
What is an example of a Varve?
Aberogwen
UNIT 4
What is a Sandur/Outwash plain?
Flat landscape, formed by fluvioglacial deposition.
UNIT 4
What is a solifluction deposit?
During the summer permafrost melts, and becomes saturated wih water, this material begins to slowly move downhill, material orientates itself with the flow directionUNIT 4
UNIT 4
What is an example of a solifluction deposit?
Eglwysbach, just above the village, local material moves downhill
UNIT 5
What is a periglacial landscape?
Landscape that undergoes seasonal freezing and thawing
UNIT 5
What is permafrost
Ground that remains frozen for 2 or more consecutive years
UNIT 5
Where is permafrost found
Tundra environment, and areas on the fringes of past and present glacial areas, high latitudes and altitudes
UNIT 5
What are some factors that impact permafrost
Proximity to water bodies - Land in contact with bodies will remain unfrozen
Slope angle and orientation - influence amount of solar radiation received - active layer is higher depth on south facing slopes
What surface is made from - absorb more/less solar radiation
Vegetation cover - insulates ground, defends from sun’s rays, intercepts snowfall (encourages permafrost)
presence of snow - Slows freezing and thawing
UNIT 5
What percentage of the Earth’s landscape contains permafrost
25%
UNIT 5
What is the mean annual temperature needed for permafrost to occur?
-2 degrees celcius
UNIT 5
How deep can permafrost be?
up to 1500m
UNIT 5
What is the active layer
Thin layer of soil on top of permafrost that can thaw, plants grow here
UNIT 5
Why is there more permafrost at the poles
at poles, there is lower temperature, as less of the sun’s insolation reaches poles
UNIT 5
What is continuous permafrost?
Forms in the colder areas of the world, where temperatures are below -6 degrees Celsius, extending down hundreds of meters
UNIT 5
What is sporadic permafrost?
Like continuous but fragmented and thinner
UNIT 5
What is discontinuous permafrost?
Occurs at margins of periglacial environments and is fragmented and only a few meters thick
UNIT 5
Why is the melting of permafrost so detrimental to climate change
Permafrost contains lots of methane, due to dead organisms being broken down during anabolic respiration the melting of which releases it.
UNIT 5
What are some negative impacts of permafrost melting?
- Permafrost is a habitat
- Infrastructure built on top will be destroyed
- Negative feedback loops - albedo
- If climate returns to normal, permafrost may still melt
UNIT 5
What percentage of animals live in permafrost environments
Half
UNIT 5
If permafrost melts, how many miles of habitats will be lost
9 million miles
UNIT 5
What makes methane worse for global warming then carbon dioxide
Methane is 25x more potent, meaning high global warming potential
UNIT 5
What is cryoturbation
Ground is mixed and broken (involutions) up by frost shattering
UNIT 5
What is segregated ice, how is it formed
forms in active layer, when freezing rates are unequal, due to capillary movement, when water moves up, towards freezing front
UNIT 5
How is pore ice formed?
Develops in pore space between sediment particle
UNIT 5
What is needle ice?
narrow ice slivers, up to several cm long
UNIT 5
How is needle ice formed?
form in moist soils overnight
UNIT 5
What is an ice lenses
cause up doming of ground (earth hummocks) during frost heave, up to several meters in high and diameter
UNIT 5
Explain the formation of an ice lenses
bodies of ice are formed when moisture, mixed within soil or rock, accumulates in a localised zone, because rates of freezing are unequal in the active layer
UNIT 5
What are ice wedges
downward narrowing lens, up to 3 meters wide and extend below ground up to 10 meter
UNIT 5
Explain the formation of ice wedges
In winter, ice is in the crack, in summer, this ice thaws, in the second winter Water freezes and expands by 9%, forming layer, annual freezing and thawing causes expansion, ridges form as sediment is pushed off.
UNIT 5
Explain the formation of ice wedge polygons
Ground contracts and cracks in winter, in summer crack fill with water, this freezes and keeps the cracks open
UNIT 5
What is patterned ground?
stones arranged in geometric shapes, (stripes, circles and polygons)
UNIT 5
Explain why stones move to the surface in periglacial environments?
Ground will freeze downwards, stones are good conductors of heat, so when temperatures drop and expanding ground begins to lift the stone. Small amounts of moisture beneath the stone freeze and turn into ice, expanding by 9%. Cryostatic pressure, raises the stone (frost heave). Ice thaws, wet sediment slumps into gap beneath the stone, after many repetitions, stones break through the surface.
UNIT 5
What happens after stones break through the surface
Sones roll to the base of mound, steep hills, cause stripes, gradual gradients form polygons or circles
UNIT 5
Why are patterns formed in patterned ground?
Different patterns are formed by the topography of the ground (rocks roll)
UNIT 5
What is a pingo
Ice cored hill, height of 3 to 70m, diameter of 30 to 1000m.
UNIT 5
What is a closed system, what is an open system
Closed - no transfer in or out
Open - transfer in or out
UNIT 5
What is the largest pingo
Kadleroshilik Pingo, Alaska, 54m high
UNIT 5
Where are closed system pingos found, where are open system pingos found
Closed - continuous permafrost
Open - discontinuous permafrost
UNIT 5
Explain stage 1 open system pingo formation
Groundwater is confined beneath the permafrost. It finds a weakness in the permafrost and rises due to artesian pressure. As the water rises, it cools and freezes, if it reaches the surface by summer it may form a spring.
UNIT 5
Explain stage 2 of open system pingo
During winter the rising water freezes before reaching the active layer, forming an ice lens. As more groundwater rises from below the permafrost, it grows, displacing the overlying sediment, forming a domed ice hill, known as an open system pingo
UNIT 5
Explain stage 1 of closed system pingo
Lakes form withing active layer during summer months, during winter this begins to freeze. Unfrozen water and lake sediment insulate the underlying ground, preventing ground from freezing (talik)
UNIT 5
Explain stage 2 of a closed system pingo
During cold, permafrost advances, encroach on Talik, liquid water freezes, becoming an ice lens. Ice lens grows, exerting cryostatic pressure, displacing overlying lake, sediment at bottom of lake now covers top.
UNIT 5
What is a thermokarst landscape
irregular surfaces, marshy hollows and depressions
UNIT 5
What is a thermokarst landscape formed by
Permafrost thawing due to warming climate.
UNIT 5
What is solifluction, what is this caused by
Wet, saturated active layer moves slowly downhill, due to gravity
UNIT 5
What is beaded draining in a thermokaust landscape
Due to unequal thawing patterns of active layer, leading to small pools of meltwater, interlocked by small streams
UNIT 5
What are thermokaust lakes
Formed in a depression by meltwater from thawing permafrost
UNIT 5
What is one cause of thermokaust lakes
Pingo collapse, water cannot percolate downwards into impermeable permafrost
UNIT 5
Explain pingo collapse
Temperatures warm, increased meltwater, ice lens begins to be exposed, solifluction of sediment in both directions atop the ice lens occurs, causing a depression when ice lens is reduced.
UNIT 5
What is the Batagay crater, where is it, what is happening to it
In russia, permafrost is melting, forming a crater
UNIT 5
What is causing the batagay crater?
Global warming - artic warms 2x faster (artic amplification)
South facing slopes experiencing most melting
mass solifluction
UNIT 5
What proportion of Russia has permafrost?
Over half
UNIT 5
What is the problem with melting permafrost in Russia?
In villages like bataguy, the ground gives way and buildings collapse
UNIT 5
How much is the bataguy crater increasing each year?
10-15cm
UNIT 5
What is a block field
surface covered by large angular rocks, product of freeze thaw on a flat plateau
UNIT 5
What is an example of a block field
Glyder Fawr - Nant Ffrancon valley
UNIT 5
What is a scree slope, example
An accumulation of freeze thawed weathered rocks at the base of a cliff, Nant Ffrancon valley
UNIT 5
Explain the formation of a scree slope
Freeze thaw occurs at the top of a drop, this reduces slope angle, overtime weathered rock from the top accumulates at the base
UNIT 5
Explain the formation of a protalus Rampart, Example
Same formation as a scree slope, but with added ice in the middle, this causes rocks to build up around the ice. When the ice melts, a bulge in a slope is left. Cwm Idwal
UNIT 5
What type of mass movement is saturated soil moving due to gravity
Soliflucation
UNIT 5
Outline the process of solifluction
Active layer thaws, permafrost remains frozen, surface layer becomes water logged because water cannot infiltrate and percolate into permafrost.
UNIT 5
Explain frost creep
On slopes, during summer, the active layer thaws, in winter, when this freezes, it expands outwards (frost heave), during the next summer, particles drop vertically, forming terracettes
UNIT 5
Explain solifluction sheets and lobes
Solifluction occurs at different rates due to the topography of the land, causing lobes and sheets to be formed
UNIT 5
Where can scree slopes, protalus ramparts, solifluction lobes, terracettes be found
Nant Ffrancon valley
UNIT 5
Explain the formation of dry valleys in periglacial environments
Develop in areas of permeable rock in active layer, surrounded by permafrost, When ice masses retreat, meltwater erodes and deepens river ‘V’ shaped valleys, when permafrost has melted, water can infiltrate, reducing surface run off and leaving river valley dry
UNIT 5
Give an example of a dry valley
Yorkshire dales
UNIT 5
What is Loess deposits
Fine rock debris transported (deflation) and deposited by winds, creating flat plateaus
UNIT 5
Explain Loess deposits
derived from glacial abrasion, which is transported by meltwater to sandurs, during colder months, large parts of the sandur will dry out, exposed to strong winds
UNIT 5
How can wind impact of glacial depris
Loess deposit
Abrasion
