Processer Flashcards
What are the glacial processes and the basic sequence of these?
Erosion - transport - deposition
What are erosional processes?
Abrasion
Glaciotectonism (Bulldozing/squeezing/thrusting)
Quarrying and plucking
Meltwater erosion
What is abrasion
An erosional process where basal debris scratches the bedrock (?).
Produces silt
When is abrasion strongest?
When there is thick ice, high basal velocity, warm based ice
What is glaciotectonism?
Bulldozing, squeezing, thrusting ect. of the existing sediments.
It is typically on soft beds
What is quarrying and plucking?
It is the process of incorporating bedrock or frozen sediments into the glacier. Done by breaking (with help from freezing) and picking up the pieces
What is Meltwater erosion and what are the sources of water?
Erosion by water from the melting of ice of the glacier.
It is either basal melting or surface ablation.
How does Meltwater move on/in the glacier?
It can move on the surface, but will most likely enter crevasses or moulins(sinkholes), into the englacial system. This will end up in the subglacial drainage system with the basal melting.
In what way does the ice transport material?
Entrainment/incorporation by:
- freezing to the ice sole (/bed)
- shearing and folding into the basal ice (detaching into the ice)
- rock avalanches from the valley sides
What are the 4 transport modes/zones?
Subraglacial
Englacial
Basal
Subglacial
Where does the subraglacial material come from?
From:
Avalanches
Wind-blown
Up-sheared
Volcanic
(Cosmic (meteorites))
How is the material transported supraglacial?
It can be carried on the top (resulting in no rounding of the rocks) and in crevasses
Where does the material in the basal transport come from, and what does it look like?
Eroded material from local substratum.
It will be abraded (rounded, scratched, bullet-shaped)
Where does the material from the englacial transport come from?
Either lowered from the surface (supraglacial) or uplifted from the ice bed (basal(?))
There will not be a lot - mostly clean ice!
How does the subglacial transport work?
It affects the underlying soft/water-saturated/unconsolidated material by the ice movement/sheer stressed - deforming it (deformation till)
What are Meltwater deposits?
Deposits from meltwater = outwash deposits, and glacialfluvial deposits
There will be meltwater both penetrating and on top of the ice.
Always sorting of the sediments
What are the characteristics of ice contact deposits (including supra- and subglacial deposits)?
- extremely variable grain sizes
- interfingering with tills
- often deformed due to ice melting (folding, faulting)
- forms steep-sided landforms
- petrographical composition similar to till by the same glacier
What is Jökullhlaups?
A type of catastrophic release of meltwater from ice-dammed lakes
What is the difference between the ice in glaciomarine and glaciolacustrine environments?
Glaciomarine:
Steep ice margin
Cracking- generating icebergs
Calm water
Glaciolacustrine:
Ice margin at one side and typographic high on the other
What causes water stratification?
Temperature changes in summer and winter, and salinity changes (marine)
Winter: surface ice-> salt expelled -> density increase
Summer: ice melt-> density decrease
Water stratification may not be present in glaciolacustrine
