Flashcards
PW 3
Flashcards do conjunto (17)
- 1What is the concept of the pressuren melting point?-All ice melts at 0oC
-Unless it is under pressure
-When under pressure, ice can melt at sub-zero temperatures
-Pressure melting point (PMP)
-Atmospheric pressure- melting point = 0oC
-Beneath 1km of ice- melting point -0.7oC - 2How could a glacier be warm (temperate)?-Ice everywhere is at the pressure melting point
-Apart from the surface which is subkect to seasonal fluctuations.
-Liquid water at the base of a glacier - 3How can a glacier be cold (polar)?-Ice is polar than the pressure melting point throughout and is therefore frozen to the bed
-No water is present - 4Can a glacier be both warm and cold?Yes, polythermal
-Warm and cold parts of the glacier
-Warm inner regions but cold at the surface and margins - 5Why may there be warm ice at the bed?-Friction, glacier is moving and is sliding at the base layer
-Sliding generates friction, friction generates heat
-Geothermal heat can cause melting
-Volcano - 6Why is the thermal regime of a glacier important?-Thermal regime affects the permeability of the ice
which influences when and where water can flow through the glacier
-The distribution of water within a glacier and the pressure at which it is present has major implications for glacier movement
When and how a glacier moves affects its ability to erode, transport and deposit debris
Thus influencing the morphology of the landscape around us. - 7Where are the following glaciers found: Super Sub EnglacialExactly where you'd expect
On top
Underneath
In the middle - 8How does supraglacial runoff occur?-Vertical and lateral percolation through snowpack
- 9How does water flow through a glacier?-When the 3 ice crystals join it forms a little gap
-Gap holds water
-Flow is very slow because gaps don’t line up
-Moulin networks - 10—1) Bulk movement with deforming till
-If glacier is on sediment will move with
2) Porewater flow
-Will move between sediment
3) Pipe flow
Bed of the glacier- channels transport the water
4) Channel network
Bed of the glacier- channels transport the water
5) Linked cavities
-Moves over bedrock/bumps this fills with water and therefore they are linked together
6) Braided canals
-Unstable
7) Film flow
Mm thick layer at the bed
- 11What is the difference between distributed and discrete features?-Distributed
-Occur across the bed of the glacier
-Linked cavities, film flow, pore water, canals
-Discrete
-Exist only at specific places at the bed of the glacier
-Channels/conduits - 12What are the primary and secondary permeability of glaciers?-Primary
-Between ice crystals
-Capillaries
-Veins
-Secondary
-Pipes
-Fractures
-Conduits
-Canals
-Linked cavities - 13How do cold based glaciers differ?Ice becomes impermeable
-No subglacial drainage
-Ice below the PMP, therefore no liquid water at bed
-Only surface runoff and meltwater directed to slides of glacier - 14What is a polythermal glacier?-Both warn and cold sections of ice
-Water has to pass through cold ice before reaching the warm ice at the glacier bed and emerging from the snout of the glacier - 15What is proglacial hydrology?-Hydrological dynamics of Proglacial Rivers represent the time and spatially integrated output from the supraglacial, englacial and subglacial environments
- 16Is a subglacial drainage static?-No, continually evolving throughout the melt season
-During the winter when there is very little melt, subglacial runoff flows slowly through a system of linked cavities
-As the summer melt season develops a greater quantity of runoff
-Travels to the glacier bed and begins to melt cavities until they coalesce into one pipe
-End of summer, most glacier bed supports a channelized drainage system, rapidly evacuating water from the bed of the glacier
-When the melt stops, volume of runoff declines and conduits become squeezed closed by ice - 17How does subglacial hydrology affect ice movement?-Key issue is water pressure
-The distributed system of linked cavities conveys water under high pressure
-Lifts parts of the glacier from the bed and help them to slide forward
-During summer when there is lots of meltwater and drainage system is formed of a discrete network of large conduits, water is conveyed at lower pressure
-Glacier is firmly on its bed and there is no enhanced forward motion by cavity sliding
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- FlashCards sobre PW 3, criado por erossmae em 25-08-2015.
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- erossmae
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