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Glaciers. Glacier. a thick ice mass that originates on land from the accumulation, compaction, and recrystallization of snow. Agents of erosion – acquire, transport and deposit sediment Occupy ~10% of land area “Interrupts” hydrologic cycle by “locking up” water. Glacier Types.

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glacier
Glacier
  • a thick ice mass that originates on land from the accumulation, compaction, and recrystallization of snow.
  • Agents of erosion – acquire, transport and deposit sediment
  • Occupy ~10% of land area
  • “Interrupts” hydrologic cycle by “locking up” water
glacier types
Glacier Types

1. Valley (Alpine)

  • Found in mountainous areas
  • Smaller than ice sheets
  • Lengths greater than widths
  • Only cover a small region
  • Transform V-shaped valleys into U -shaped valleys
glacier types1
Glacier Types

2. Ice sheets (Continental glacier)

  • Large scale – cover 10% of Earth’s land
  • Found in polar regions
    • Greenland – 1.7 million km2
    • Antarctica – 13.9 million km2
slide7

Daily Questions

Upslope

  • The images were taken at the same location but with 59 years between the photos.
  • Which direction is the ice moving (upslope or downslope)?
  • Which direction is the glacier moving (upslope or downslope)?
  • Is there a difference between the directions – explain.

Downslope

Upslope

Downslope

Fig. 16.3

glacier movement
Glacier movement
  • Gravity primary force
  • Entire ice sheet moves 5 to 50 m/yr
    • Plastic flow – flowing solid
    • Basal slip– movement over bedrock
  • Fastest movement within the center
  • Friction Slows down the sides
slide9

Glacier movement

20 meters

100 meters

glacier budget
Glacier Budget

In -Zone of accumulation

Snow accumulates and forms ice

Outer limit is the snowline

Out – Zone of wastage

ablation – general term for loss of ice or snow from a glacier

  • Sublimation
  • Melting
  • Evaporation
  • Calving - icebergs
glacier budget1
Glacier budget

Zone of Accumulation

Zone ofWastage

  • If ice formation is greater than ice loss – glacier advances downslope
  • If ice formation is less than ice loss – glacier retreats upslope
  • If ice formation is = ice loss – glacier position is stationary
glacier erosion and deposition
Glacier Erosion and Deposition

Plucking – loosen and lift blocks of rock (mechanical weathering)

Abrasion – sediment in ice acts as giant “sandpaper”

Creates Rock flour – very fine-grained material

Creates Striations – grooves scratched in bedrock that indicate direction of ice movement

causes of glaciation
Causes of Glaciation
  • Full Reasoning is not known
  • Theory of Glaciation needs to include:
    • Interglacial periods – periods of warm climate separating periods of glacial advancements.
causes of glaciation1
Causes of Glaciation
  • Full Reasoning is not known
  • Theory of Glaciation needs to include:
    • Interglacial periods – periods of warm climate separating periods of glacial advancements.
    • Glacial episodes in the Paleozoic (200-300 mya) and Precambrian time (700 mya).
causes of glaciation2
Causes of Glaciation
  • Full Reasoning is not known
  • Theory of Glaciation needs to include:
    • Interglacial periods – periods of warm climate separating periods of glacial advancements.
    • Glacial episodes in the Paleozoic (200-300 mya) and Precambrian time (700 mya).
    • Earth’s average global is 14oC, in the geologic past it was 22oC – Glaciation requires a temp. of about 10oC.
    • Continental glaciers originate in polar or elevated land.
    • Sufficient precipitation needs to occur.
milankovitch cycles
Milankovitch cycles
  • Earth’s orbital changes controls its climate
  • Eccentricity
    • Measure of the nooncircularity of Earth's orbit
    • Cycle is about 100,000 years
milankovitch cycles1
Milankovitch cycles
  • Eccentricity
  • Inclination
    • The changes in the axial tilt (22o to 24.5o) of the Earth
    • The greater the tilt the greater the contrast between summer and winter temperatures
    • Cycle is about 41,000 years
milankovitch cycles2
Milankovitch cycles
  • Eccentricity
  • Inclination
  • Precession
    • The wobble of the Earth as it spins on its axis
    • Cycle is about 26,000 years
milankovitch cycles3
Milankovitch cycles
  • Main effect of cycles is to change the contrast in the temperature of the summer and winter.
  • Glaciation would occur when the summer temperature is closer to the winter temperature, but winter temperature are not colder than usual.
  • Rather the mild summers melt less ice than is received in the winter.