Glaciation Flashcards
Name 4/6 periglacial processes
Nivation, frost heave, freeze thaw weathering, solifluction, high winds, meltwater erosion
Name 3 unique periglacial landforms
Ice wedges
Patterned ground
Pingos
Name the processes of accumulation
Direct snowfall
Avalanches
Wind deposition
Name the processes of ablation
Melting
Sublimation
Calving
Evaporation
Avalanches
What are 3 processes important in the movement of glaciers
Basal slip
Regelation creep
Internal deformation
What are the 5 factors that control the rate of movement
- Altitude
- Slope angle/ gradient
- Ice thickness
- Bedrock Permeability
- Variations in mass balance - ice temp, ablation rate etc.
Name glacial erosion processes
Quarrying
Plucking
Abrasion
Crushing
Basal melting
Name 5/7 upland erosional features
- corries
- aretes
- pyramidal peaks
- truncated spurs
- glacial troughs
- hanging valley
- ribbon lakes
Name 4 landforms due to ice sheet scouring
Roches moutonees, whalebacks, knock and lochan, crag and tail
What are 3 reasons for glacial deposition
- when the velocity is reduced
- when ablation increases
- when they become overloaded with debris
Name ice contact depositional features
- erratics
- medial moraines
- lateral moraines
- recessional moraines
- terminal moraines
- drumlins
Name lowland depositional features
Lodgement till and Ablation till
Name three fluvial glacial ice contact features
- kames
- eskers
- kame terraces
Name 4 fluvial glacial proglacial features
- sandurs
- pro glacial lakes
- meltwater channels
- kettle holes
What are epochs?
Periods of geological time
What two epochs is the Quaternary period broken down into
- Pleistocene, the beginning - 11,500 yrs ago
- Holocene (the age of man) 11,500 - now
Causes of long term glacial and interglacial cycles
- Milankovitch Theory:
- Eccentricity - elliptical to more circular orbit and back
- Axial tilt - angle changes impacting the intensity of light received therefore seasonality
- Precession (wobble) - wobbles on its axis changing the point long term change to seasonality
MILANKOVITCH CYCLES MAY TRIGGER CHANGE HOWEVER FEEDBACK MECHANISMS CAN MAGNIFY THEM LEADING US IN AND OUT OF GLACIAL PERIODS!
Causes of short term climate change
- Sunspots vary the energy emitted by the sun
- Volcanic causes alter temp due to ejecting huge amount of ash, sulphur dioxide and co2 spreading out and blocking sunlight
Examples of short term climate events
- The Loch Lomond Stadial - climate fluctuations caused two stadiums of ice advance separated by an interstadial
- The Little Ice Age - period of cooling
What is the cryosphere?
Part of the earth’s crust and atmosphere subject to temperatures below 0 degrees for some part of the year. Made up of land surfaces and frozen areas of lakes and rivers. They act as stores within the global hydrological cycle.
What are the four different characteristics when classifying ice mass?
- Ice sheets, vast expanses of ice covering land surfaces
- Ice caps, smaller masses of ice, often associated with mountain ranges
- Glaciers - cirque glaciers (small) valley glaciers (larger)
- Ice fields - large expanse covering mountainous regions and interconnected glaciers
Characteristics of warm based/ temperate glaciers
- high altitude areas
- basal ice is the same temperature as the pressure melting point so the bottom melts continually
- lots of debris in ice - subglacial deposits and landforms
Character of cold based/ polar glaciers
- high latitude areas
- remains permanently frozen to bed
- with less debris in it
What is the pressure melting point
The temperature at which ice begins to melt under a given amount of pressure.
(Water melts at 0 degrees, when under ordinary atmospheric conditions. At higher pressures, the melting point of water is lower, meaning it remains a liquid at below its ordinary freezing point.
What are the four main types of cold environment
- Polar (high latitude) regions - areas of permanent ice e.g. Antartica and Greenland ice sheet
- Periglacial (tundra) regions - characterised by permafrost e.g. Alaska, Scandinavia
- Alpine/ Mountain (high altitude) regions - e.g. the Alps, Himalayas and glaciated landscapes
- Glacial environments - at the edges of ice sheets and in the highest mountainous regions, e.g. the Himalayas
Is the glacial system an open or closed system?
open
What is the accumulation zone and where does it occur?
Where there is a net GAIN of ice over the course of the year - the inputs exceed the outputs
Occurs at the top of the glacier
What is the ablation zone and where does it occur?
Where there is a net LOSS of ice during the year - the outputs exceed the inputs
Occurs at the glacial snout
What is the zone of equilibrium?
A balance between accumulation and ablation
What are the 4 factors that can affect the zone of equilibrium?
- Rate of accumulation/ ablation
- Time of year/ season
- Glacier will retreat when ablation> accumulation
- Glacier will advance when accumulation> ablation
What does accumulation include?
- Direct snowfall
- Avalanches
- Wind deposition
What does ablation include?
- Melting - water
- Sublimation
- Evaporation
- Calving
What is the glacial mass balance?
The balance between accumulation and ablation determine whether a glacier grows or shrinks.
What is basal sliding?
Where the meltwater beneath the glacier acts as a lubricant so the glacier can move - only warm based glaciers.
What is regelation slip?
Process of melting and refreezing of ice over small deposits that depends on pressure.
What is extensional flow?
increase in gradient causes for basal sliding to increase, ice to accelerate and become stretched and thinner
What is compressional flow?
Reductions in gradient, basal slip slows, piles up and thickens.
What are transverse crevasses?
When the glacier speeds up transverse crevasses occur and stretch in the direction of flow and fan across the glacier.
What are longitudinal crevasses?
When the ice slows down longitudinal crevasses form parallel to the flow these can spread out sideways and cover a larger area.
What are marginal and radial crevasses?
When glaciers turn a corner there is friction between the valley wall and glacier and these form near the side.
What is sub-glacial bed deformation?
If a glacier moves over a softer or weaker rock its rock can deform under glacier and because it is soft the glacier may speed up.
What is internal deformation?
The weight of the glacier causes ice crystals to deform so the glacier moves slowly downslope or individual layers of the glacier move forward.
What are the 5 factors that impact the rate of movement
ALTITUDE
SLOPE
LITHOLOGY
SIZE
MASS BALANCE
What are the 5 factors that glacial erosion consist of
abrasion
plucking
fracture and traction
dilation
meltwater erosion
Define abrasion
The physical wearing and grinding of a surface through friction and impact by material carried in water or ice
Define plucking
Basal ice freezes in rock surface cracks, as the main body of the glacial ice moves around, the ice in the cracks is pulled and plucked out
Define dilation
occurs when the removal of weight from above reduced the pressure on the bedrock causing it to adjust and crack and fractures open up
What are the 6 factors affecting glacial erosion
Ice slope and gradient
Ice temperature
Ice thickeness
Precipitation levels
Rates of ablation
bedrock permeability
Name 6 macro glacial features
Corrie
U shaped Valley
Hanging valley
Truncated Spur
Arete
Pyramidal Peak
What is an arete
A sharp knife like ridge that separates two cirques on a mountain
What is a pyramidal peak
Where three or more cirques erode a mountain
What is a truncated spur
spurs on a hillside that have effectively been removed by glacial flow
What is a U-shaped valley
Occur web the glacier has carved through a mountain valley straightening, widening and deepening it as it goes
What are hanging valleys
Where the main glaciers eroded a trough deeper and wider than smaller glaciers joining it. Hanging valleys along side of large trough which an have waterfalls on them.
Example of a u shaped valley and hanging valley.
Little Langdale off great Langdale
Where can ribbon lakes form
Along the bae of glacial troughs
What are the three steps to corrie formation
- Snow accumulates in a nivation hollow and it stays there where year after year it compresses into ice
- Freeze-thaw weathering and plucking of the back wall causes it to steepen and abrasion helps to deepen the bottom
- Eventually the ice melts creating the potential for a tarn/lake depending on rock type.
Name 4 meso-scale features
Whalebacks
Roches Moutnonnées
Knock and Lochan
Crag and Tail
What are Whalebacks
Streamlined features where a glacier moves over a resistant rock hill and abrades it
What are Roches Mountonnées
Stoss and Lee feature, formed beneath warm based ice with abundant melt water, abraded on stoss side and plucked on their lee side
Describe Crag and Tail
Produced by erosion and deposition beneath ice sheet
The Crag (hill) is usually a strong rock that has resisted glacial erosion.
Describe Knock and Lochan
They occur due to alternating bands of hard and soft rock which allow differential erosion in a glacially sourced lowland area
Where can Knock and Lochan landscapes be found
Scotland and Canada
Name three micro features
Striations
Chatter marks
Crescentic Gouges
Describe Striations
Scratches in the bedrock caused by the ice dragging debris across the surface
Describe Chattermarks
Irregular chips and fractures in the rock
Describe Crescentic Gouges
Like chatter marks with a regular crescentic pattern, concave stoss facing feature
What three things do micro features help us to understand
The direction of ice, provenance and ice extent
What are 5 geomorphological processes in glaciation
Freeze thaw
Solution/carbonation
Meltwaters erosion
Mass movement
Frost heave
Describe freeze thaw weathering
When water enters cracks in rocks and freezes, the water expands by 9% and overtime forces to widen crack and break the rock
This can form scree and block weathering
Describe solution/carbonation
At lower temperature CO2 is more soluble in the atmosphere and can dissolve into rainwater forming acid rain which and react with limestone and dissolve the rock.
Describe meltwater erosion
Water can travel under hydrostatic pressure and effectively erode rocks like limestone
describe frost heave
The upward movement of sediment and soil due to the freeze thaw action within the soil, it can cause stones to rise through the soil as larger material moves downwards.
describe mass movement
The large-scale movement of weathered material in response to gravity.
what percentage does water expand by when frozen
9%
Describe and explain erratics
Debris carried by a glacier which is of different rock type to the bedrock it now rests on. Can show provenance
What are the 4 main processes of glacial deposition
Lodgement
Ablation
Deformation
Flow
Describe lodgement till and how it occurs
Occurs beneath ice mass when subglacial material gets LODGED in the glacier bed
Describe ablation till and how it occurs
Due to the glacier melting and no longer carrying debris so it is dumped.
can be characterised by unsorted material
Describe deformation till and how it occurs
When the sediment is defined by the movement of the glacier.
Can produce rock flour
Describe flow till and how it occurs
Occurs in high meltwater content causing the glacial debris to FLOW during deposition
Can produce rock flour
What are the 6 different types of moraine
Lateral
Terminal
Medial
Ground
Recessional
Hummocky
Describe drumlins
Drumlims primarily consist of lodgement till and occur in swarms typically found, basket of eggs topography in lowland areas.
A greater elongation suggests the more powerful ice flow
Describe lateral moraines
Material derived from freeze thaw at the valley side and carried at side of glacier
Describe medial moraines
Found in the centre of glacier, where two lateral moraines join together
Describe terminal moraines
Marks the maximum extent of advancement found at glacial snout
Describe ground moraines
Materail dragged underneath glacier
Describe push moraines
Occurs if glacier re-advances and deposited material is PUSHED forward
Describe recessional moraines
Form behind terminal moraines and mark stages of glacier retreat when it remained stationary
Describe hummocky moraines
Chaotic grouped of mounds that are though to form when ice thins an material is deposited
What are drumlins and moraines
ice contact features
What are then two main sources of meltwater
Surface melting
Basal melting
What five things does meltwater play a vital role in
- erosion
- transportation
- deposition
- basal sliding
- sub glacial bed deformation
Describe basal melting
Occurs under hydrostatic pressure in warm based glaciers and can travel through subglacial tunnels eroding and cutting through bedrock
What are the three characteristics of fluvial glacial deposits
smoother and rounder
sorted horizontally
stratified vertically
What are four landforms of fluvio glacial deposits
Kame Terraces
Kame Deltas
Eskers
Kames
What are four fluvial pro glacial landforms
Kettle holes
Braided streams
Varves
Sandurs
Explain the formation of eskers
Formed from material in subglacial tunnels as meltwater supply decreases, when glacier retreats material is deposited at a constant rate and forms a ridge
Explain formation of Kame Terraces
During summer valley sides radiate heat and melt the edges of the glacier forming meltwater streams which deposit sediment
When the glacier retreats the sediment will fall to the valley floor forming kame terraces
Explain formation of
kames
As meltwater streams meerde into proglacial lakes velocity drops and sediment is deposited in the centre/middle of glacier
Describe and explain Kettle Holes
As glacier retreats, detached blocks of ice remain in outwash plain. Meltwater streams flow over the ice covering them in deposits. Eventually ice melts and debris subsided forming depression which fills with meltwater forming a lake
Small circular lakes in the outwash plain
Describe Sandures
The flat expanse of fluvioglacial sediment in a proglacial area
Describe Varves
Sediment found at the bottom of lakes
How do proglacial lakes form
By meltwater trapped against an ice sheet or by the damming action of a moraine or ice dam during the retreat of a melting glacier
Describe a meltwater channel
A narrow channel cut into the bedrock underneath or along the ice margin. Meltwater can erode deep channels as a result of hydrostatic pressure and can flow
What are four aspects of periglacial tundra environments
- contains permafrost
- not permanently covered by ice
- high altitude and latitude
- on the marginal fringes of polar environments
What is talik
unfrozen ground
What are four periglacial processes
freeze thaw weathering
ground ice
solifluction
nivation
Describe the formation of ice wedge polygons
They are formed by the refreezing of the active layer during winter causing soil to contract and cracks to open. During the melting in the summer the cracks fill up with meltwater and sediment then they refreeze widening and deepening crack.
What is continuous permafrost
frozen ground
What is discontinuous permafrost
mostly frozen ground
what is sporadic permafrost
only bits of frozen ground
Where is permafrost distributed
on the fringes of polar regions in subarctic conditions
Describe the formation of patterned ground (step by step)
- frost push caused by hydraulic action propels the stones upwards and frost heave causes stones to migrate outwards forming circles
- the up doming of the circle created by the heaving means that larger stones roll outwards and finer sediment is in the centre due to gravity
Describe the formation of a closed pingo
- a frozen lake with sediment on the floor insulates the ground beneath from the cold, this allows the talik to exist
-Over winter, ground water underneath the lake sediments within the Talik (unfrozen ground) can be trapped by ice from the lake surface as the lake freezes, and advancing permafrost within the ground. This decrease in temperature causes this ground water to freeze into an ice lens, which grows over time as water freezes to the ice lens due to the increase in hydrostatic pressure. This causes the sediment above to bulge upward into the characteristic pingo shape.
What are the two main differences between closed and open pingos
closed - CONTINUOUS PERMAFROST, WATER THAT FROMS ICE LENS FROM WITHIN
open - DISCONTINUOUS PERMAFROST, WATER THAT COMES FROM OUTSIDE OF THE SYSTEM
Describe the formation of an open pingo
The active layer continually freezes and melts year on year above the permafrost and talik. Over winter, as the active layer freezes down over water can become trapped between the descending freezing plane of the active layer and the permafrost that surrounds it. This promotes the growth of an ice lens which pushes the land up above it as it expands. Water underneath the permafrost can move through the talik between the permafrost areas because of capillary action (the movement of water through the soil because of ) and hydraulic pressure. This water migrates to the ice lens and freezes, swelling the ground above further.
What can happen if a pingo becomes too large
The ground can crack and expose the ice lens to the suns energy, this melts the ice and causes the pingo to collapse. Leaving a ruptured pingo with a depression in the middle that can fill with water and become a lake.
Where is can closed system pingos be found
Mckenzie delta canada
Where can open pingos be found
lowlands of eastern Greenland
How do scree/talus slopes form
When rock fragments fall and accumulate on the lower slopes or base of cliffs
the larger the material the steeper the angle
What is solifluction
The downhill flow of saturated soil common in periglacial areas
What is frost creep
the very slow form of movement as material moves downslope
What is important about asymmetric valleys
That the differential rates of solifluction and frost creep lead to one side being steeper than the other.
What are frost creep and solifluction examples of
mass movement
Describe the role of wind action in periglacial environments
Sediments can be blow southwards and deposited
e.g. sediments were blown over large areas of Europe and north America which formed soils of high agricultural potential
e..g gobi desert
Describe the formation of a nivation hollow
When snow accumulates in a hollow and due to temperature it does not melt, so year after year it grows and turns into ice tin lower layers. Eventually the ice begins to move under its own weight downhill and erode the ground to form a hollow
Describe the role of meltwater in periglacial environments
Water erosion is highly seasonal and therefore changeable
Due to the melting of the active layer, there can be periods of high discharge, this can usually cause braided rivers due to high amount of material carried
Case study - Canada periglacial region
tundra environment seasonal processes
winters dark and cold
short summers snow and soil layers above permafrost melt, this feeds wetlands and streams and rivers
Case study - Canada periglacial region
impact of climate change on tundra (5 POINTS)
- changing dramatically due to global warming
- animals that are typically found further south (red fox) are moving onto tundra now competing with other species (artic fox) for food and territory
- permafrost is foundation for unique ecosystem and permafrost is deteriorating with warmer climate
- melting of permafrost can contribute to global warming - 14% carbon in permafrost
- TUNDRA HAS FLIPPED FROM BEING A CARBON SINK TO A CARBON CONTRIBUTOR, BEGINNING TO CONTRIBUTE TO THE BUILD UP!!
Case study - Canada periglacial region
impact on humans
- short term, foundation of houses and infrastructure on permafrost can causes subsidence and collapse
Case study - Canada periglacial region
negativeimpact on environment (5)
- as soils soften the water in the ice leaks out
- lakes and ponds drain
- co2 and methane realised from ground
- animals struggle as invasive species move in
- potential feedback mechanisms kick in
Case study - Canada periglacial region
what is the potential feedback mechanism caused by climate change
AIR TEMP INCREASE - GROUND WARMS UP - PERMAFROST MELTS - STORED CARBON AND METHANE RELEASED, repeated
