Glaciation Part 1 Flashcards
Glacial
A prolonged cold climate phase that lasts tens of thousands of years and causes continental glaciation in middle and high latitudes.
Inter-glacial
A period of climatic warming ( lasting 10,000 years) between glacials.
Ice age
A period of cold climate
Holocene
Lasts 12,000 years- since end of last ice age.
Epoch
Period of time
Quaternary
A geographical period ranging from 2.6 may to modern day.
Cryosphere
The frozen water part of the earth’s system
Glacier
A large mass of moving ice and snow on land
Ablation
Changing from ice to a liquid or gas
Where in the would can we find ice sheets?
Greenland and Antarctica
What are the inputs of a glacial system?
Precipitation, material, thermal, kinetic and potential energy.
What are the throughputs in a glacial system?
Gravitational energy, frictional energy and release of latent heat.
What percentage of the earths surface is covered in ice?
10%
How often do ice ages occur?
Every 200-500 million years.
Albedo
The reflection of solar radiation by the earths surface.
Accumulation
The build up of snow or precipitation over a period of time.
Negative feedback
The system will self-regulate to re-establish stability through counteracting the change and will maintain a state of equilibrium.
Positive feedback
A change creates a response in the system reinforces the effect of the original change, creating a snowball effect which can lead to a new state of equilibrium.
Positive mass balance
Accumulation > ablation
Usually occurs in winter and glacier advances.
Negative mass balance
Ablation > accumulation
Usually occurs in summer and glacier retreats.
Mitigation
Reduce the effect of something
Open system
A system in which matter can enter and escape to the surroundings.
Closed system
A system in which no matter is allowed to enter or leave.
Aeolian processes
Wind can carry out erosion, transpiration and deposition which can shape glaciated landscapes.
What are the factors affecting glaciated landscapes?
Wind, precipitation and temperature.
Ventifacts
A landform formed by the rock being eroded by the wind.
Lithology
What rocks are made of. The chemical and physical composition.
What are the types of cracks?
Jointing, faulting, bedding and pores
What is the snow line?
The lower edge of permanent snow cover in upland areas.
How is a glacier formed?
accumulation occurs which creates a low density layer. Where temperatures are low enough the snow will remain frozen throughout the year which will compact to a firn. Air is forced out which makes the glacier even denser.
What are the 2 zones at a glacier?
Accumulation zone- higher up
Ablation zone- lower down
What is the end of a glacier called?
Snout
What are the outputs of a glacial system?
Ablation, calving, deposition and thermal energy.
What are the factors influencing the decay of ice sheets?
Decay is a result of ablation, where summer temperatures are high and a loss of ice from calving.
What are the short term variations in mass balances?
It can vary throughout the year. But typical glaciers get more accumulation in winter and more ablation in summer.
Ice sheets
On land.
Thick or thin.
Greenland and Antarctica
Sea ice
On sea
Thick
Arctic
How do high latitudes affect glaciated landscapes?
High latitudes are high pressure bands with low levels of cloud and precipitation. So less accumulation for glaciers.
What is the temperature decrease rate as altitude increases?
Temperature decreases at a rate of 6 degrees per km.
How is faulting caused?
By tectonic movement.
How is jointing caused?
Due to stress
How is pores caused?
When water gets trapped in the rock, and freezes. It expands by 9%. The cracks get bigger overtime.
Impact of relief on glacial systems
When there is a steeper relief there is more potential energy meaning that the glacier will have more energy to move faster.
Plateaus
Flat land at high altitudes
Tidewater glaciers
A valley glacier that reaches the sea. Forms small ice burgs
Iceberg
A floating mass of ice that has been calved or broken off from the snout of a glacier.
Outlet glacier
A glacier flowing out from an ice sheet, ice cap, or ice field.
Tributary glacier
A small glacier flowing into a large glacier.
Where does a glacier move the fastest?
Middle and the top of the glacier as there is less frictional resistance to move. The frictional resistance is from the rocks at the base.
What are the characteristics of ice?
When solid and rigid the ice tends to break.
When under steady pressure the ice will deform and behave like plastic.
Pressure melting point
The temperature at which ice is in the verge of melting at a given point.
Characteristics of a warm glacier
High altitude.
High accumulation of snow in winter and ablation in summer
Steep gradient
Powerful erosion
Moves mainly by basal slippage.
Characteristics of a cold glacier
High latitude
Low relief
Limited ablation and accumulation as there is little seasonal variation.
Moves by internal deformation.
What is the example of a cold based glacier?
Meserve glacier in Antarctica
What is the example for a cold based glacier?
Athabasca glacier in Canada
How much does a cold glacier move per day?
1-2 cm
How much does a warm based glacier move per day?
2-3 metres
What do cold based glaciers mainly move by?
Internal deformation:
Intergranular flow
Laminar flow
Inter-granular flow
Individual ice crystals re-oriantate and move in relation to each other.
Laminar flow
The movement of individuals layers between the glacier.
What do warm based glaciers mainly move by?
Basal slippage:
Regelation slip
Creep
Bed deformation
Regelation slip
On the upside of an obstacle the pressure builds up causing local melting. This lubricates the movement of the ice as it reduces friction.
Creep
If ice encounters a large obstacle on bedrock floor it is put under increased stain so deforms plastically and flows around the obstacle.
Bed deformation
When ice is carried by saturated bed sediments moving beneath it. Water is then under high pressure.
Extending flow
When ice moves over a sleep slope it can’t deform quickly and so fractures forming crevasses. The leading ice pulls away from the ice behind it.
Compressing flow
As the gradient is reduced, ice thickens and the follow ice pushes over the slower-moving leading ice.
Glacial surges and example
Short events where a glacier can advance substantially, moving at velocities up to 100 times faster than normal.
For example the Disko bay in Greenland that moved 10km in 4 years.
What can cause glacial surges?
Hydrological (sudden increase in meltwater)
Deformable bed hypothesis (unconsummated sediment fails under stress)
Critical mass (being met and basal melting reducing friction)
Crevasses
Features formed in the surface of the ice as it moves
Marginal crevasses
These are a result of friction along the valley sides as the ice advances
Transverse crevasses
Extend along a glacier- common as ice falls
Longitudinal crevasses
Valley becomes wider and ice surface widens to fill the valley
Radial crevasses
Found at the snout of a glacier.
As it moves out onto the open land and no longer constrained by the valley
