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Flashcards

Glacier mass balance

Emily H Geography - English 34 cards

Cards in this deck (34)

  1. 1Accumulation zoneInputs exceed outputs
    Steep slopes = more avalanches
    High altitude+ relief = relief snowfall
    Low temperatures = little melting
  2. 2Ablation zoneOutputs exceed inputs
    Higher temperature = increased melting
  3. 3StoresWhere material is held - ice, water + debris accumulations
    Debris accumulates on top of the glacier from the valley sides as it moves down the valley it becomes embedded in the glacier as layers of snowfall are compressed on top >> causes ROTATIONAL SCOURING as bands of slowly rotating rocks are scraped over the bedrock
  4. 4Flows/ transfersMovement of ice, water and debris
  5. 5ProcessesInternal deformation
    Basal sliding
  6. 6Internal deformationCold-based glaciers
    Gravity + internal pressure causes layers of ice crystals to slide over each other forming parallel planes (crumpling deformation) forming deep crevasses at the surface
  7. 7Basal slidingWarm-based glaciers
    Higher temperatures cause more melting so higher quantities of meltwater
    Lubricates between lowest ice level and bedrock
    Meltwater flows through the glacier - vertically through moulins or beneath it
    As the basal ice encounters more resistant bedrock where pressure builds up and melts the ice due to increasing temperature
  8. 8TransportSupraglacial = along top of glacier
    Englacial = inside
    Subglacial = under glacier/ ice sheet
  9. 9ErosionAbrasion
    Plucking
  10. 10AbrasionRocks and debris carried by glacier scrape along valley floor as it moves down the valley under gravity
    Striations in bedrock
    Picks up eroded material as it moves
  11. 11PluckingMeltwater flowing along the base of the glacier freezes to bedrock which is then ripped out by the moving glacier
  12. 12Sediment (depositional features)Till
    Fluvioglacial
    Moraines
  13. 13TillI sorted material deposited directly by glacial ice
  14. 14FluvioglacialSediment deposited by flowing meltwater from the glacier
    Formed kames (mounds of material in the depression behind a glacier) or eskers (narrow winding ridge of material on the valley floor)
  15. 15MorainesLateral
    Unconsolidated glacial debris
    Side of glacier
    Medial
    Junction of 2
    Terminal
    Shout
    Recessional
    Perpendicular to lateral
  16. 16Glacier mass balance/ budgetDifference between accumulation and ablation over a year
  17. 17AccumulationDirect precipitation
    Blown snow and avalanches
    Rain and meltwater percolating through snow and refreezing
    Inputs transferred down glacier due to gravity
  18. 18AblationLoss of ice and snow through melting evaporation sublimation and calving
  19. 19Positive glacier mass budgetNet gain of ice
    Glacier advances
    Equilibrium line moves down valley
  20. 20Negative glacier mass budgetNet loss of ice
    Glacier retreats up-valley
  21. 21Seasonal variationsAccumulation exceeds ablation in winter
    Although less precipitation as less evaporation, fewer outputs of meltwater and water vapour + greater proportion of precipitation snow
    Ablation exceeds accumulation in summer
  22. 22Not constant due to changing weather conditions each yearClimate change longer-term changes
    E.g. retreating due to global warming - overall ablation exceeds accumulation as more mass lost in meltwater and water vapour
  23. 23FACTORS INFLUENCING GLACIATED LANDSCAPESClimate
    Latitude and altitude
    Relief and aspect
    Geology
  24. 24WindAeolian processes act on fine till and fluvioglacial material
    (= erosional, transportational and depositional processes by the wind as it is a moving force)
    Aids erosion of rocks and transports fine material into system Increases inputs
    Adds to erosive capabilities of glacier
    Adds to debris accumulations which erodes away rock as it advances
    Increases kinetic energy > more erosion + transportation
  25. 25PrecipitationMain input of snow sleet and rain (increases inputs > positive budget when outputs low)
    Large seasonal differences (jasper national park 75mm more in June than January > more varied mass balance than Antarctica)
    Varies by location (high latitude low precipitation- high pressure at poles but high at high altitude- relief precipitation
    Freeze-thaw weathering dur to rainwater > adds to glacial material + increases erosion
    Adds to throughputs - greater stores of ice (flow through system)
  26. 26TemperatureHigher = more melting and evaporation (meltwater > fluvioglacial)
    Summer snowmelt high altitude (always cold high latitude)
    Higher temps summer increase precipitation (vapour rises and condenses)
    Temperature high latitude may never rise above 0 so ice sheets thick despite low precipitation due to minimal outputs
    More ice accumulation- throughputs
    Meltwater moves through system quicker than ice
    Hot house conditions
    Glacials/ interglacials
  27. 27High latitudesColder as lower insolation
    Arctic and Antarctic circles cold dry climates with little seasonal variation in precipitation
    Glaciers develop under influence of large stable ice sheets e.g. Greenland, Antarctica
    Mass balance reasonably constant throughout year > larger glacier with high erosive power (minimal outputs so still positive budget)
  28. 28Low latitude, high altitudeLandscapes develop under dynamic valley glaciers e.g. Rocky Mountains
    Higher precipitation inputs (relief) but greater outputs + summer melting due to more variable temperatures
    Significant decrease in temp with altitude (1 degree 100m) - Pastoruri glacier Peru 10 degrees from equator (but melted a lot recently dur to global warmimg)
  29. 29Steeper reliefGreater resultant force of gravity - more gravitational potential energy so greater kinetic energy creating greater erosive force > increases throughputs (debris accumulation) as eroded material transported into glacier
  30. 30Aspect faces away from SunNorth facing slopes northern hemisphere
    Temps below 0 for longe as less insolation so less melting > more likely to be positive and glacier advances shaping landscape more dramatically
  31. 31Aspect towards SunMore meltwater, water vapour, fluvioglacial
  32. 32MY
  33. 33Lithology Physical and chemical composition of rocks > affects impact of weathering, erosion and mass movementHighly resistant rock e.g. basalt (dense interlocking crystals)more likely to form prominent glacial landforms (arrête, pyramidal peak)
    Weak lithology e.g. clay (weak bonds so little resistance) - increases erosion adding material to glacier (limestone vulnerable to chemical weathering due to calcium carbonate > carbonation)
    > more vulnerable to erosion and mass movement - add gravitational potential energy + more deposited as fluvioglacial
  34. 34Structure Properties of individual rock typesJointing = break in layer/ body of rock
    Bedding plane = layers of sedimentary rock
    Faults
    >> more vulnerable to erosion - freeze-thaw/ frost shattering
    Permeability
    Primary permeability- pores absorb and store water
    Secondary permeability e.g. water seeps into carboniferous limestone due to many joints - enlarged by solution
    Impermeable rocks may reduce flow of meltwater through system
    Rock angles of dip influence valley side profiles e.g. horizontal bedded layers of sedimentary rock (strata) support steep cliffs
    Strata incline profiles follow angle of dip of bedding plane - steeper landscape increases gravitational potential energy providing greater erosive power + increases inputs e.g. avalanches (snow+debris)

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- Geography (Glaciers) Flashcards on Glacier mass balance, created by Emily H on 01/11/2018.
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