Unit 3 Notes Flashcards
What is the first stage of freeze thaw weathering?
Water enters a crack in a rock, as temperature goes below 0 degrees, it expands by 9%.
What is the second stage of freeze thaw weathering?
Cryostatic pressure is exerted on a rock, and cracks begin to get bigger, as water solidifies.
What is the third stage of freeze thaw weathering?
Temperature fluctuates either side of 0 degrees, and cracks begin to get bigger, and the process repeats.
What is the fourth step of freeze thaw weathering?
Process is repeated multiple times, as more pressure is exerted, and rock fractures.
What is cryostatic pressure?
Pressure exerted onto a rock, as ice freezes.
What are porous rocks?
Rocks with holes in.
What are the conditions needed for freeze thaw weathering?
Porous rocks, pervious rocks, temperature fluctuations above and below 0 degrees.
What are pervious rocks?
Rocks with cracks.
What is abrasion?
Weathered debris of a rock scraping against the bedrock, wearing it away, leading to the rock becoming smooth. Sub glacial debris is worn down and converted into rock flour.
Which factors affect glacial erosion?
Speed of glacier movement, supply of debris, ice thickness, shape of debris, subglacial meltwater, hardness of debris and bedrock.
How does speed of glacier movement affect abrasion?
The more rapid the rate of movement, the more rapid the rate of abrasion. Faster moving glacier may scratch the surface more.
How does supply of debris affect abrasion?
More supply of debris means a greater rate of abrasion.
How does ice thickness affect abrasion?
At the base of the glacier, there is more pressure going downwards, when rock scrapes against the bed.
How does shape of debris affect abrasion?
The more angular the debris, the more it erodes.
How does subglacial meltwater affect erosion?
Enables basal sliding, which is necessary for abrasion, and more meltwater reduces abrasion.
Which factors lead to the most abrasion?
High speed, hard debris, with lots of supply, subglacial meltwater is present, angular debris.
How does hardness of debris affect abrasion?
Softer rock is more easily eroded, Debris which is harder than bedrock leads to more erosion.
Which rocks are susceptible to plucking?
Highly jointed or fractured rocks.
How does plucking occur on the down valley side of the glacier?
As ice is moving over by the process of regelation slip.
Why is plucking effective at the base of a glacier?
The presence of meltwater due to pressure melting.
How does sub glacial meltwater erosion work?
Meltwater may be more channelled beneath a glacier, before emerging at the snout.
Why are subglacial streams more powerful than ordinary streams?
Increased hydrostatic pressure.
Why is there more hydrostatic pressure?
They are confined beneath the glacier, so they’re under immense amounts of pressure, as they’re constricted.
Why are subglacial discharge patterns different to normal?
They’re dependent on temperature fluctuations rather than precipitation channels. They flow slowest in winter, as temperature is reduced at night time, so melting is reduced.
