Glaciers: Part 1

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Evidence for Glaciers-the small stuff

• Erratics!
• Unsorted material
• Striations
• Polished Bedrock

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Erratic-A boulder-sized rock dumped by a
glacier. The rock is usually of a different type
that the surrounding rock
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Unsorted Materials-all sizes mixed together.
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Striations-Grooves carved into the bedrock by
pebbles and cobbles carried at the bottom of a
glacier.
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Glacial Polish-Smooth rock surfaces created as
glaciers flow over bedrock.
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Glacial Pavement.
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Conditions for Glacier Formation

• Cold Summers!!
• Located above the snow line, or in polar regions.
• Presently occupy 10 of worlds total land area
  (32 during ICE AGES)
• Form on all continents BUT Australia

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Snow becomes Firn
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Process of Glacier Formation

• Snow does NOT melt in summer
• Recrystallization of snow to form LARGE crystals
  of ice (rough and granular)
• called FIRN liked packed snowballs
• Lower layers turn to SOLID ICE under the weight
  of overlying firn and snow.

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Glaciers Types

• VALLEY GLACIERS long, slow-moving, wedge-shaped
  streams of ice found in alpine areas (high
  elevation)
• small 1-2 km long, 100s m wide, 100s m deep
• largest Over 100kms long X 100s m deep
  
• CONTINENTAL GLACIER (ICE SHEETS) very old
  (1000s of years), thick (1000s of meters) mass
  of ice covering almost an entire land mass
• GREENLAND 1.7 Million SQ MI , 3 KM thick
• ANTARCTIC 12.5 Million SQ MI, 5 KM thick

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Landscape Features- Valley Glaciers -the BIG
stuff

• CIRQUES semi-circular shaped bedrock feature
  created as a glacier scours back toward the
  mountain (1st place snow and ice accumulate)
• ARÊTES steep-sided, sharp-edged bedrock ridge
  formed by two glaciers eroding away on opposite
  sides of a ridge
• HORNS 3 or more cirques adjacent to one another
• TARNS glacial lakes produced by glacial
  scouring- often found in cirques

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ARÊTE
CIRQUE
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CIRQUE
TARN
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Landscape Features- Valley Glaciers-the BIG
stuff

• HANGING VALLEY valley eroded by a small
  tributary glacier floor is at a higher elevation
  that valley it feeds into
• U-SHAPED VALLEY a glacially eroded valley also
  called a glacial trough

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ARÊTE
CIRQUE
HANGING VALLEY
U-SHAPED VALLEY
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Glaciers Movement

• What makes them move?
• WEIGHT the weight of the overlying mass forces
  the ice to spread out.
• FLOW ice is slippery! Flows over underlying
  rock/soil
• speed is like a stream faster in middle/less
  friction
• fastest movement after heavy winters, steep
  slopes, and in summer
• CREVASSES form along steep slopes

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FASTEST
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A CREVASSE- Evidence of movement
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Glaciers Movement

• How far do they move?
• BELOW SNOWLINE Glaciers begin to melt and
  evaporate, thinning out (lower elevation/latitude)
  
• ICEFRONT the front edge of a glacier
• MELTINGMOVEMENT Stationary Ice Front
• EXTEND TO THE SEA break off CALVING

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Glaciers Movement

• What do they move?
• LOOSE ROCK any size, picked up from underlying
  land
• FALL-IN rocks fall in from surrounding elevation
• TRIBUTARY GLACIERS carried from smaller,
  surrounding glaciers

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CONTINENTAL ICE SHEETS
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CONTINENTAL GLACIERS FEATURES

• MORAINES rock build-up in a glacier
• Ground Moraine carried in the bottom of a
  glacier pre-deposition
• Lateral Moraine pile up along the sides
• Medial moraine material within the glacier (two
  come together)
• End moraine occurs at the ice front
• ROCK FLOUR fine sand and silt crushed from rock
• GLACIAL MILK meltwater carrying Rock Flour!

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Glacial Deposits whats left?

• DRIFT all deposits of glacial origin.
• TILL unsorted/unstratified material left by
  GLACIERS.
• OUTWASH deposits made by streams after glaciers
  melt (sorted/stratified)

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Glacial Deposits whats left?

• MORAINES after all the ice recedes, piles of
  sediment are deposited.
• RECESSIONAL MORAINE slowly retreat of end
  moraine leaves smaller rows of sediments behind.
• TERMINAL MORAINE deposit marking the glaciers
  farthest advance.

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Kettle Lake
Drumlins
Esker
Outwash plain
Till
Moraine-dammed lake
Glacial Stream
Terminal Moraine
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Long Island- Terminal Moraine
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