Glaciation Flashcards
Most recent ice age?
When was it?
Pleistocene epoch, occurred in the quaternary period.
2.5M - 11,700 years ago
What are the fluctuations in temperature called during the ice age?
Glacials - colder temperatures - ice house earth
Interglacials - warmer temperatures - green house earth
How long do glacial periods last for?
Glacials and interglacials tend to last for around 100 000 years
How long did the last glacial maximum last for?
How much of the earth was covered in ice?
How far did it advance?
29 000 to 19 000 years ago
8%
Northern Europe - covered Northern UK and the south experience periglacial conditions.
What period are we currently in?
We are in the Holocene epoch which is an interglacial period lasting over 10 000 years.
Remaining ice covered areas are in polar, alpine and periglacial regions.
What is ‘the little ice age’?
It was a stadial
Despite being in an interglacial period temperatures continue to fluctuate.
A significant decrease occurred between 1300 and 1870 known as the little ice age. Thames froze over.
What are stadials?
When was the most recent?
A stadial is a short pulse of ice advance.
The most recent stadial was called the Loch Lomond stadial which was completed 1000 years ago.
Long term causes of Glacial Periods?
Milankovich cycles
Tectonic Movements
What are the different types of milankovich cycles?
How long do they last?
What affect do they have?
Changes in eccentricity every 95 000 years.
From circular to eliptical.
Glacials occur during circular orbits
Interglacials occur during eliptical orbits
Changes in tilt - changes between 21.8 degrees and 24.4 degrees every 41 000 years.
Great tilt = interglacial
Changes in wobble/ axial precision
Every 22 000 years the earth’s axis describes a circle.
Changes where the suns solar energy is distributed.
These cause long term climate change
How do variations in solar output affect climate change?
There are sunspots on the sun’s surface which indicate more solar radiation is being emitted.
Cycles last 11 years
Short term affects
How does tectonic movement affect climate?
Changes in ocean currents lead to more moisture in the north.
This leads to more snowfall
Snow has a high albedo and therefore reflects more of the suns solar radiation
Less is absorbed leading to a temperature decrease
This is a positive feedback loop and this causes long term change
How does volcanic activity affect climate change?
Example
Volcanic eruptions emit ash and SO2 into the stratosphere and are spread around by wind.
They have high albedo leading to the sun’s solar radiation being reflected.
Leads to lower temperautres.
Tambura, 1985 - called the ‘year without summer**
What is the cryosphere?
Importance?
The frozen part of earth’s hydrological system
Regulates temperature utilising high albedo of snow and ice
What are ice sheets?
These are vast expanses of ice - 1km thick which cover land surface.
They can extend over the sea to form ice shelves
What are ice caps?
These are smaller masses of ice often associated with mountain ranges
What are the different types of glacial environment?
Alpine - eg. European alps - Large temp range with high precipitation
Periglacial - eg. Northern Canada - edge of permanent ice
Polar terrestrial - very low temp - very low precipitation eg. arctic
Polar Marine - extensive sea ice
How are glaciers formed?
When there is more snow accumulation than ablation.
Over periods of 20-30 years snow turns into glacial ice
Compaction from weight above and melting then refreezing increases its density.
As density increases the O2 content decreases
If there is more ablation than accumulation then there is a ?
Negative mass balance and the glacier retreats
What are the different types of glaciers x7
Piedmont
Cirque/corrie
Ice sheet
Ice cap
Ice shelf
Niche
Valley
Characteristics of an ice sheet
Example
Largest type of glacier not constrained by topography but spreads out from a central dome shape
East Antarctic
Characteristics of an ice cap
Example
Large glacier not constrained by topography
Vatnajokull
Characteristics of an ice shelf
Example
An area attatched to an ice sheet which spreads out over the ocean
Larsen B
Characteristics of a piedmont glacier
Example
A glacier which spreads out in a bulbous shape once it leaves the constrains of the valley.
Malaspina glacier
Characteristics of sea ice
Example
Top layer of sea freezes and floats on top - Not a glacier
Arctic ocean
Characteristics of a cirque/corrie
Occupies a large bowl shaped hollow on one side of a mountain
The eel glacier
Characteristics of a valley glacier
Travels downslope in a similar way to a river, is constrained by valley walls
Characteristics of a niche glacier?
A very small glacier occuping a hollow high up in a mountain
What is the snowline?
Lowest point of permanent yearly snow and ice cover
Define mass balance?
How much ice is gained or lost in a year
What evidence is there for the Pleistocene ice age?
Depositional features such as Drumlins, morraines and erratics -cumbria
Erosional features found in the cairngorms including corries and arretes.
Meltwater channels
what are the 2 forms of glacial movement?
Basal flow
Internal deformation
What is basal sliding?
A movement processes which involves the glacier sliding along the bedrock with the aid of meltwater as a lubricant.
The meltwater is produced due to increased pressure due to ice mass from above leading to a decreased melting point called a PMP.
1-2 m per day
Occurs in temperate glaciers.
What is internal deformation?
Very slow movement of the ice due to its polycrystalline structure. Crystals move individually due to the force of gravity.
1-2 cm per day
Occurs in polar glaciers.
What is regelation creep?
When a glacier encounters an obstacle pressure is built up on the stoss side which results in the PMP being met and the production of meltwater occurs. Basal sliding can now occur
Meltwater then refreezes on the lee side of the obstacle where pressure is reduced.
What is extending flow?
Occurs when valley gradient steepens and ice accelerates under the force of gravity.
Ice becomes thinner and the rate of erosion decreases.
Crevasses form.
What is compressing flow?
Occurs when valley gradient decreases and ice decelerates causing ice to pile up and become thicker.
Erosion rate increases
Crevasses close.
What factors affect the rate of ice movment? x6
Altitude - Changes precipitation levels and temperature therefore changing the mass balance.
Gravity - steeper gradient = faster ice flow
Friction - glaciers flow fastest in the centre away from effects of friction
Ice mass - Heavier glaciers can create PMP causing more basal sliding
Meltwater - basal sliding
Ice temperature - temperate glaciers move faster
Characteristics of temperate glacier
Speed
Temp
Location
Movement
Erosional capability
1-2 m per day
-10
Alps
Basal sliding
High
Characteristics of polar glacier
Speed
Temp
Location
Movement
Erosional capability
1-2 cm per day
-1.6
Antarctica
Internal deformation
Low
What are the 2 main types of glacial erosion
Abrasion due to entrained material which scour the landscape leaving striations and scratches.
Plucking or quarrying occurs when meltwater refreezes part of the bedrock and then as the glacier moves forward it ‘plucks’ it from the bedrock.
What are the different locations material is found?
Subglacial
Supraglacial
Englacial
Proglacial
Difference between pre and post glacial landscapes
U shaped valleys instead of v shaped
Valley sides steeper and smoother
What is a corrie?
Enlarged, deep hollow on a mountain side
Steep back wall with scree at base
A lip which has a tarn behind it
What is an arrete and pyrmidal peak
arrete = 2 corries back2back
3 or more corries = pyramidal peak
What is a glacial trough?
Steep sided, flat bottomed valley.
Mainly straight due to the erosive power and inflexibility of the glaciers that form them
Misfit streams
Stepped profile caused by tributary glaciers.
How does a ribbon lake form?
Due to localised over deepening of the valley floor creating a stepped profile.
The over deepening can be down to weaker bedrock, merging of a tributary glacier or the narrowing of the valley which leads to thicker ice.
Different places where glacial landforms can be found?
Subglacial
Marginal
Proglacial
Periglacial
Two main forms of glacial erosion?
Abrasion - Freeze thaw weathering creates sharp angular pieces of rock which become entrained. As they stick out the bottom and sides of the glacier they grind over and scour the landscape. Forming striations - (useful for determining ice flow)
Over time they become pulverised forming rock flour
Plucking - When basal meltwater freezes around part of underlying bedrock and then when the glacier slips forward it pulls part of the bedrock away.
Very common where regelation creep occurs due to localised pressure.
Types of landforms associated with cirque and valley glaciers?
Corries - arete/pyramidal peak
Glacial troughs
Truncated spurs/Hanging valleys
Ribbon lakes
What is a corrie? and how is it formed?
Enlarged, deep hollow on a mountain side.
Steep cliff like backwall with a pile of scree at its base. Also has a raised rock lip in front of the hollow which often allows a tarn to form.
Found where there is great accumulation of snow and ice.
As it begins to flow basal/rotational sliding begin abrasion and plucking which deepens the hollow.
Debris is pushed to the edges of the hollow which form the rock lip.
Eg. Helvellyn Corrie in the Lake District
How are aretes and pyramidal peaks formed?
Aretes - Knife like ridge formed between two corries that are b2b
eg. Striding edge
If three meet this is called a pyramidal peak eg.Matterhorn
What determines Corrie orientation?
In the N hemisphere nearly all Corries are orientated between NE and NW this is because:
- Northern slopes receive much less solar insolation so glaciers last longer - more chance for erosion
- Western slopes face the sea and blow relatively warmer winds which also melt the glaciers.
What is a glacial trough?
Characteristics?
Formation?
U shaped valleys that are:
Steep sided
Deep
Flat bottomed
Largely straight - due to the erosive power and inflexibility of the valley glaciers
Stepped profile caused by tributary glaciers
Create ribbon lakes
Large mass of the glacier leads to immense erosive power mainly via abrasion
What is a Hanging Valley
How is it formed?
When a smaller tributary glacier meets the main glacial trough at a higher elevation (due to less erosive power) a hanging valley is formed.
How are ribbon lakes formed?
Formed by localised over deepening of glacial troughs.
Deep and narrow lakes
This occurs when the glacial trough gains more erosive power due to:
- Weaker bedrock allowing more vertical erosion
- Merging of a tributary glacier adding to the mass and erosive power of the original glacier
- Narrowing of the valley leading to thicker ice and more vertical erosion
How are truncated spurs formed?
In a preglacial valley a river flows around interlocking spurs of rock.
When a glacial trough then flows through the valley it is less flexible and has more erosive power then the river and therefore it erodes the interlocking sections of rock.
This leaves behind blunt steep valley sides.
Abrasion is the main erosive force here however plucking and freeze thaw weathering also occur.
What landforms are a result of ice sheet scouring?
Roche Moutounnees
Knock and Lochan landscapes
Crag and tail
How does a crag and tail form?
Formed as a result of underlying geology
When a large section of resistant rock obstructs the flow of a glacier.
This forces the glacier to go around the stoss section leading to regelation creep and plucking of this section
Leeward side of less resistant rock is protected by the crag and this leads to a gently sloping tail of deposited material
macro scale feature
Roche moutonnee formation?
Bare outcrops of rock with a smooth stoss side with striations as a result of abrasion and a plucked lee side.
Increased pressure on the stoss side as the resistant rock causes localised pressure melting which leads to basal sliding.
Reduced pressure on the lee slide causes meltwater to refreeze (relegation creep) and plucking occurs
meso scale feature
What causes a knock and lochan?
Scoured and rugged lowland features.
Formed of alternating roch moutonee with no vegetation followed by erosive hollows that are filled with small lakes.
Knocks are resistant bedrock hills and the lochs are example of over deepening of less resistant areas.
macro scale landform
Glacial depostion causes which landforms?
Medial, lateral, recessional and terminal morraines
Drumlins
Till plains
Lodgment till
Ablation till
Erratics
(Crag and tail)
What is a generic morraine?
Generic term for landforms associated with glacial deposition of till which is:
- Angular and unsorted
What are the different types of moraine?
Ground
Terminal
Recessional
Lateral
Medial
What is ground moraine?
Sediment transported subglacially and is deposited over underlying bedrock over a large area on the valley floor
What is terminal morraine?
A ridge of sediment piled up at the furthest extent of glacial movement.
Runs perpendicular to the direction of glacial movement
What is recessional morraine?
Retreating glaciers may experience periods of stability and re advance and form a new ridge at the snout.
What is lateral morraine?
Forms along the edge of glaciers from material that falls or slumps from the valley wall.
What is a medial morraine?
Formed when lateral moraines from merging glaciers join up.
They leave a ridge down the middle of the glacier during deposition
What are drumlins?
Elongated hills made of glacial till aligned in the direction of glacial flow
Form beneath the glacier when it meets and obstruction and till is deposited as ground moraine.
Moraine then shaped by the moving ice which follows direction of flow
Consists of a steeper, blunt stoss end followed by lee slope with a tapered tail
Multiple drumlins are known as a swarm
What are the lowland depositional features?
Till plain
Lodgement till
Ablation till
What is a till plain?
When the glacier retreats, till is deposited over a vast areas across the valley floor
Meltwater flows out the glacial snout forming meltwater rivers. These meltwater rivers pick up some of the till and further erode it via attrition.
These are then deposited in a sorted way when the river loses velocity.
This fine sediment forms a glacial outwash plain
What is lodgment till?
Material that is carried subglacially which is forced and lodged back into bedrock below
What is ablation till?
Material that is carried englacially or supraglacially is deposited when the glacial is stagnant or retreating
What is till fabric analysis?
Involves the study of the orientation of glacially deposited material
By measuring the orientation of deposited material over and over again we can figure out direction of glacial flow.
What are erratics?
Boulders of rock which are deposited far from their origin
Why are landforms of glacial deposition useful?
They can help determine the direction and extent of ice movement
Till fabric analysis
Drumlin orientation
Erratics
Terminal and lateral moraine
Can also help indicate ice mass
eg. crag and tail as a macro landscape needs a large ice mass to form
What are the different processes of water movement within glaciers?
Supraglacial channels - on top of glaciers
Englacial channels - within glaciers
Subglacial channels - under glaciers
Meltwater discharge is high during summer months (when there is a negative mass balance)
What are the two distinctive types of fluvioglacial landforms?
Ice contact features:
Kames
Eskers
Kame terraces
Proglacial features
Sandurs/Outwash plains
Pro glacial lakes
Melwater channels
Kettle holes
How does an esker form?
Long, winding ridges of sand and gravel running parallel to the glacier
Formed from deposition of subglacial meltwater streams
What are kames?
Mounds of sand and gravel found on the glacier valley floor.
Supraglacial meltwater streams collect in surface depressions and deposit layers of debris. As the glacier retreats it leaves these mounds
Kame terraces - formed from material being deposited by meltwater channels running between glacier and valley sides - These are sorted with heavier material on the bottom
Crevasse kames - small hummocks on valley floor as sediment is left in small crevasses.
What is a sandur/outwash plain/
Gent sloping area of sand and gravel
Formed in the pro glacial region as material is carried and deposited via meltwater streams
Sediment is sorted with the heaviest sediment being transported closest to the glacier.
Sediment is laid down annually in the summer
How are proglacial lakes formed?
When ice sheets expand and dam rivers they can form proglacial lakes.
Deposited moraine can also form pro glacial lakes
What are kettle holes?
Hollows formed when large blocks of ice left from glacial retreat are covered by deposits of sediment from meltwater streams.
When the ice melts a depression is left which then fills with water to from a kettle hole
Differences between glacial and fluvioglacial deposits?
Fluvioglacial deposits are stratified - there are defined layers due to variations in seasonal accumulation of sediment
Glacial deposits are unstratified
Fluvioglacial deposits are sorted as the larger, heavier sediment is deposited first
Glacial deposits are unsorted
Fluvioglacial deposits are smooth and round due to attrition
Glacial deposits are angular as well as being of various shapes and sizes.
What is a varve?
A distinct layer of silt lying on top of a layer of sand
What are the values of Antartica?
Tourism
Scientific Research
Ecosystem
Water store
Value of Tourism in Antarctica
How many tourists annually?
100 000 tourists per year as of 2024 - Number has increased since tourism began in 1960
Provides an eye opening experience with the aim of tourists going away with greater ecological sensitivity
Provides economic revenue and job opportunities for travel providers who are mainly based in South America
Who regulates tourism in Antarctica?
What’s their aim?
Rules?
International Association of Antarctic Tour Operators - IAATO
Emphasise low impact and sustainable travel
- 1:20 ratio of operators to tourists
- 5m distance regulation from wildlife
- Sanitation procedures
What’s the value of scientific research in Antarctica?
How many research stations are in Antarctica?
70+ research stations from 30 different countries
Climate change research - Ice cores hold climate records going back 800 000 years.
Changes in Antarctica’s climate indicate major changes to come in Earth’s global climate.
Monitoring of glacial movement - This can help predict global sea rise.
Value of Antarctica as an Ecosystem?
Unique habitats such as Krill which feed on algae under the sea ice.
Krill is vital in the global food chain
How much of the Earth’s freshwater is stored in Antarctica?
70%
Threats to Antarctica?
Tourism
Climate Change
How is tourism a threat to Antarctica?
Tourists can bring invasive species, these can alter the ecosystem due to increased competition.
Bird breeding season coincides with tourist season.
There are examples of birds no longer nesting in areas where tourists visit.
Ships bringing tourists can leak oil which can damage ecosystems.
How is climate change a threat to Antarctica?
Global warming on the Antarctic Peninsula is 3x faster than the global average.
Rising temp is melting the sea ice which has a knock on effect. eg. Krill which feed on algae under sea ice have decline in number by 80% since 1980. This has lead to a decline in the number of Adelie Penguins (eat krill).
Melting ice has also lead to sea level rise which can have severe impacts to coastal settlements.
How is the Antarctic managed?
International Association of Antarctic Tour Operators - IAATO
Scientific Committee on Antarctic Research - SCAR
Antarctic Treaty
What is the Antarctic Treaty?
When?
Aim?
How?
Treaty created in 1959 with originally 12 countries (now 59) with an aim to ensure peace and preserve the continent’s environment whilst permitting scientific research.
Consists of many articles including:
- No territorial claims
- Peaceful purposes only
- Freedom of scientific investigationl,
What’s the Paris Agreement?
Global treaty adopted in 2015 in order to control climate change.
Main aims:
- Limit global warming to +2 degrees
- Cut greenhouse emissions
- Provide financial support to developing countries in order to help them meet their climate goals
Issues with managing Antarctica?
- Enforcement issues due to no central authority
- Increased human activity means old protocols must be redesigned or adapted
- Pressure from external sources mean the potential economic value of mining and other mineral exploitation could damage the environment
What are the economic values of the European Alps? x4
Farming - Transhumance due to seasonal climate. Large dairy industry
2015 - £8.5B revenue - 150 000 employees
Forestry - Switzerland 31% tree cover
- 90 000 employees
HEP
- 500 HEP stations in Switzerland
- 60% Switzerland’s energy is HEP
Tourism -
- 120M annual tourists
- £50B revenue
This helps boost infrastructure
What are the environmental values of the alps?
Freshwater source
Supplies many of Europe’s major rivers eg. Rhine.
Carbon Sink
- Switzerland has 31% tree cover
Biodiversity
- Home to many endemic species eg. Alpine Ibex
Natural Threats of the Alps?
Glacial Outburst Floods
- These are sudden releases of meltwater from glacial lakes.
Due to overflowing or breakdown of ice dam. Can be tectonically related.
Avalanches
Kill approximately 200 people per year
Human threats to the Alps?
Urbanisation
Tourism
Dam Construction
Global Warming
How is urbanisation and tourism having negative impacts on the Alps?
Decreasing agricultural economy and the rise of tourism has lead to urbanisation.
Many second homes, accommodation and infrastructure to support the industry is being built.
This can lead to soil erosion which increases the risk of natural hazards such as avalanches.
Its also at the expense of biodiversity.
Snow cannons are being used to produce artificial snow for the ski season.
These use chemical additives which is bad for soil and they require much water and energy.
Tourism is driving the price up as well which is forcing local people away. socioeconomic disparities
Negatives of dam construction in the alps?
Alters the natural flow of rivers - negative impact on ecosystems eg. Declining trout population
Large reservoirs can destabalise slopes which can potentially lead to increased avalanche risk.
Effect of climate change in the Alps?
Increased temperatures has led to a higher negative mass balance of glaciers.
- Increased avalanche and GOF risk.
- Loss of water supply to major European rivers eg. Rhine
- Reduced snowfall so shorter ski seasons or the reliance on snow cannons - economic losses
This is a positive feedback loop as less snow leads to darker ground which then absorbs more of the sun’s radiation.
Increased river discharge = higher flood risks
HEP Dam operations become redundant due to low level meltwater
What is the Alpine Convention?
Negatives?
Created in 1995 it aims to find a balance between economic growth and preserving environmental quality.
However, only 5 countries have ratified all the protocols.
- Switzerland has not as many of its districts believe it focuses too strongly on the environmental preservation.
Example of a local attempt to preserve the alps?
Altesa Arena, Switzerland - example of sustainable apline tourism
Lifts powered by locally sourced renewable energy
Car free
Education of tourists to become sustainable ambassadors
Eco friendly infrastructure eg. no snow cannons
What is an ice field
Areas less than 50,000 km² which have extensive regions of interconnected Valley glaciers high peaks called nunataks rise above them.
What is crushing?
When pressure exerted by ice mass and its debris crush the bedrock surface leaving chatterarks.
