Mysterious rock formations

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Mysterious rock formations.
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What could have caused these formations?

• GLACIERS!!!!!

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Evidence for Glaciers

• Erratics
• Unsorted material
• Striations
• Polished Bedrock

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Erratic
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Erratic

• Boulder-sized rock dumped by a glacier
• Rock is different type than surrounding rocks

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Unsorted Materials-all sizes mixed together.
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Striations
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Chatter marks (Maine)
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Striations/ Chatter marks

• Grooves carved into bedrock
• Formed by abrasive action of cobbles and pebbles
  carried at bottom of glacier
• Direction of scratches shows direction glacier
  moved

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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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What does a glacier look like?
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What conditions are necessary for glacial
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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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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Snow becomes Firn
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Glaciers Types

• VALLEY GLACIERS
• long, slow-moving, wedge-shaped streams of ice
• Bordered by mountains
• Size varies
• small 1-2 km long, 100s m wide, 100s m deep
• largest Over 100kms long X 100s m deep
  

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• CONTINENTAL GLACIER (ICE SHEETS)
• very old (1000s of years) and thick (1000s of
  meters)
• Not confined by mountains
• Examples
• GREENLAND 1.7 million square miles, 2 miles
  thick
• ANTARCTICA 12.5 million square miles, 3 miles
  thick

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Features associated with valley (alpine) glaciers
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Original valley (V-shaped) Glaciers come
and alter landforms Glaciers retreat and
new features appear
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Landscape Features- Valley Glaciers

• CIRQUES
• semi-circular shaped bedrock feature
• created as a glacier scours back toward the
  mountain

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• ARÊTES
• steep-sided, sharp-edged bedrock ridge
• formed by two glaciers eroding away on opposite
  sides of a ridge

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TARNS glacial lakes produced by glacial
scouring often found in cirques
CIRQUE
TARN
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• HORNS
• 3 or more cirques adjacent to one another

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Hanging Valley
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ARÊTE
CIRQUE
HANGING VALLEY
U-SHAPED VALLEY
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U-shaped valley
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CONTINENTAL GLACIERS FEATURES
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Lateral moraine
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• MORAINES material left behind when glacier
  recedes

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• When glacier retreats (melts) rock and sediments
  are dropped behind
• Long Island, Cape Cod and the islands are part of
  a terminal moraine

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Kettle Lake
Drumlins
Esker
Outwash plain
Till
Moraine-dammed lake
Glacial Stream
Terminal Moraine
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Drumlin
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drumlins
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Kettle Lakes
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River in glacier carries sediment Glacier
melts Drops sediment Esker results
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Eskers