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Geology > Glaciers & climate change > Flashcards

Glaciers & climate change Flashcards

1
Q

Why were Vikings particularly prolific from 800-1200 A.D.?

A

Warm temperatures enabled them to travel freely and inhabit Arctic lands

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2
Q

Glacial drift

A

Large rocks found far from the sources, this hindered cultivation for farmers. They were found in large valleys.

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3
Q

Erratics

A

the glacier left behind single rocks, no strata and no order

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4
Q

Louis Agassiz

A

paleontologist that measured glaciers

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5
Q

Interpretations of glacial drift

A
  1. great deluge (flood)

2. glacial origin

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6
Q

Agassiz notes about glaciers

A
  1. can carry large boulders
  2. do not sort sediment
  3. melt and leave behind deposits
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7
Q

How have glaciers affected us here in western Oregon?

A

Floods triggered by the failure of glacial dams in Montana swept down the Willamette valley and into the Eugene area

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8
Q

Transformation to glacial ice:

A
  1. accumulation and compaction
    2 initial snow- 90%
    3 ends blunted by melting or sublimation 50% air
    4 with overburden, pressure melting
    5 firm snow packed- 25% air
    6 water recrystallizes in voids - 20% air
    7 glacial ice is not transparent because of air bubbles- bluish color
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9
Q

two types of glaciers

A

alpine and continental

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10
Q

Alpine glaciers

A
  • occurs in mountainous areas

- topographic control on ice movements

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11
Q

continental

A

-spreads over large areas
-unconfined by topography
-thick
today found in Antartica and green land

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12
Q

why isn’t the north pole capped by an ice sheet?

A

there is no land to have an ice sheet on. spreads on the ocean.

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13
Q

Glacier requirements

A
  1. Cold- snow doesnt melt in the summer
  2. snowfall- accumulation
  3. gentle surface slope- accumulation without avalanches
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14
Q

what controls temperature?

A

altitude and latitude

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15
Q

Altitude

A

temperature decreases with elevation

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16
Q

Latitude

A

distance from the equator

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17
Q

result of latitude and altitude

A

glaciers are closer to sealevel near the poles

18
Q

Viscosity

A

the measure of a material’s resistance to flow

19
Q

Styles of glacier movement

A
  1. Basal sliding
  2. Internal flow
  3. Fracturing
  4. Plastic flow
20
Q

Basal Sliding

A
  • Meltwater accumulates at base of glacier
  • Fluid pressure reduces friction
  • Common in temperate glaciers (warm areas)
21
Q

Mechanisms of basal sliding

A

Regelation: on up-glacier side of obstructions, pressure melting occurs
- on down-glacier side, water refreezes

22
Q

Internal Flow

A
  • Plastic like flow
  • ice crystals deform
  • shearing- crystals slide past one another
  • polar glaciers - base frozen to ground
23
Q

Fracturing

A
  • Brittle behavior
  • ice near surface (upper 60m)
  • crevasses
24
Q

Plastic flow

A
  • below 60m depth

- Deformation is pressure dependent

25
Q

why dont glaciers flow downhill faster?

A

Sediment at their beds slow them down

26
Q

two general factors of the rate of movement

A
  1. slope

2. ice thickness

27
Q

Water is a big factor in the rate of movement

A

Temperate glaciers are faster than polar ones

28
Q

Surges

A
  • Build up of water pressure
  • short term acceleration
  • water drainage slows it down
  • velocities 20-100 m/day
29
Q

movement driven by gravity

A
  1. sloping surfaces (valley glacier)
  2. gravitational spreading
    - flat pressure builds with thickness
    - lateral movement releases pressure
30
Q

Accumulation by snowfall

A
  • upper portion of glacier

- winter snow doesnt melt

31
Q

Ablation

A

loss of ice near the base of glacier

  • sublimation
  • melting
  • calving
32
Q

Equilibrium Line

A

seperates accumulation and ablation zones

33
Q

Negative budget

A
  • ablation exceeds accumulation

- glacier retreats

34
Q

Positive budget

A

Accumulation exceeds ablation

-glacier advances

35
Q

Steady budget

A

ablation equals accumulation

-no change in size

36
Q

the velocity of glaciers tend to be slower or faster near valley walls and why?

A

they tend to be slower near the valley walls due to friction

37
Q

If the accumulation area for a glacier is 10 km2 and the ablation area is 5 km2, the status of the glacier budget is ……

A

Cannot be determined because we don’t know how much has snowed and the elevation

38
Q

Which of the following is NOT characteristic of Ice Ages?

A

More CO2

39
Q

climate fluctuations within ice ages are primarily controlled by :

A

variations in earths position and orientation relative to the sun

40
Q

Why are glaciers observed at lower elevation near the equator that at latitudes of 30 degrees North and South of the equator?

A

Rate of snowfall is higher near the equator

Geology (7 decks)

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