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1
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2
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- Glacier: A mass of snow or ice that moves under it’s own weight:
- Alpine Glacier aka Mountain or Valley Glaciers
- Continental Glacier: covers large part of continents
- Ice caps (<50,000 sq km)
- Ice Sheet (> 50,000 sq.km)
- Greenland and Antarctica ice sheets
- More than a km thick
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3
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4
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5
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- Snow Line: Altitude of year-round snow
- Snowfall must exceed summer melting
- Pole facing slopes and gentle slopes favor glaciers
- Snow(90%) ŕGranular
ice(50%)ŕ
Firn(20-30%) ŕGlacial Ice(<20%)
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6
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- Accumulation: addition of ice or snow
- Ablation: processes by which ice is lost
- Melting
- Calving: breaking of chunks of ice from glacial front
- Sublimation: evaporation of ice
- Wind erosion
- Glacial Budget: Accumulation - Ablation
- Equilibrium line: Ablation = accumulation
- Retreat and advance of glaciers
- Glacial surge
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7
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8
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- Erosion:
- U shaped valley
- Rock Flour, Striations, glacial pavement
- Cirque, Arčte
- Deposition:
- Drift: glacial deposits
- Till: deposited by ice
- Outwash: drift (re)deposited by melt water
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9
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10
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11
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12
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13
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- Moraine:
- End, Terminal, Lateral, Median, Ground Moraines
- Drumlin:
- streamlined hills of till parallel to the direction of ice flow
- 25-50 meter high, kilometer long
- Kame:
- Small hills of melt-water deposits at the edge of ice
- Varve:
- Alternating silty and clayey layer in glacial lake
- Eskers:
- Long, narrow winding ridges deposited by melt water flowing in under
the ice tunnels
- Kettles
- Hollows formed by melting of isolated glacial blocks
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14
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- Ice age: From 10 Ka to 2 Ma (Pleistocene epoch), continental glaciers
covered much larger areas than today causing cooler temperature and
lower sea level world-wide
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15
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16
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17
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- Geologic, sedimentary records e.g., Nebraska Dune, Coal Deposits,
glacial till etc
- Proportion of CaCO3 in Marine sediments
- Oxygen Isotopes
- Water Vapor: Isotopically lighter;
- Rain: heavier near source
(equator), lighter further away (polar)
- Fractionation is Temp dependent (higher at lower temperature)
- Marine shells also reflect surface water temperature
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18
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19
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20
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21
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22
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- Vostok: started 1960, reached a depth of 2755 m in 1990’s; contain
climatic records for 160 Ka.
- High 18O/16O ratio indicate warmer climate and
correlate with high CO2 and methane in trapped air bubbles
for the last 11,000 years
- Fluctuations coincide with Milankovitch Cycle
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23
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24
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25
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26
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27
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Notes