The Great Lakes

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The Great Lakes

• Brandon Dunn, Kate Thometz, Vince Amicon

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Huron Ontario Michigan Erie Superior
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THE GREAT LAKES

• Largest group of fresh water lakes worldwide
• Borders United States and Canada
• Used today as major source of transportation

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GEOLOGIC HISTORY

• Formed as a result of the Ice Age 10,000 years
  ago
• The Lauren tide Glaciation melted with rising
  temperatures and dug a whole in the Earths crust
  
• The water from the glacier filled the holes and
  became the Great Lakes
• Due to erosion, many small mountains formed the
  present-day Great Lake Islands

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Lake Superior

• Largest of the great lakes in area and volume.
• Contains 10 percent of the worlds fresh water
  supply.
• Lake Superior was formed 1.1 to 1.2 billion years
  ago during the Mid-continent Rift.
• For over 2 million years, thick flows of lava
  (flood basalts) repeatedly broke up the surface.
• During extended periods between these flows, the
  crust sank downward, creating a basin that
  accumulated sediments until the cycle began again
  with the next flood of molten lava.

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Lake Michigan

• The third largest of the lakes and sixth largest
  freshwater in the world.
• 3,200 miles of shoreline, the longest of any
  state but Alaska

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Lake Huron

• Lake Huron is the second largest Great Lake by
  surface area and the fifth largest freshwater
  lake in the world.
• Huron was the first of the Great Lakes to be
  discovered by European explorers.
• Lake Huron is surrounded by forest life and still
  has many rich natural resources.

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Background

• The Great Lakes is a group of five freshwater
  lakes in central North America. It creates a
  natural border between the United States and
  Canada.
• It is the largest body of freshwater in the
  world, with a combined surface area of 95,000 sq
  mi.
• From west to east the lakes are Lake Superior,
  Lake Michigan, Lake Huron, Lake Erie, and Lake
  Ontario.
• The distance from the western end of Lake
  Superior, to the outlet of Lake Ontario is 1,160
  mi.

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How the lakes were formed

• The Great Lakes were formed approximately at the
  end of the Pleistocene period, when the
  glacier-carved lake basins were filled with melt
  water from the retreating ice sheet.
• The lakes are connected to each other by straits,
  short rivers, and canals.
• The height above sea level of the lake surfaces
  varies from Lake Superior's 602 ft, to Lake
  Ontario's 246 ft
• The greatest sudden drop occurs at Niagara Falls
  167 ft between lakes Erie and Ontario.

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Rock Formations

• As the glaciers receded their leading edges left
  behind high ridges and incredible rock
  formations.
• There were 8-12 ice ages that formed these
  incredible rock formations like the one pictured
  are the right.
• The last glacier began to melt around 14,000
  years ago. The melting water filled the huge
  holes left by the glaciers.
• The lakes were originally much larger than they
  are now. But as more ice melted the St. Lawrence
  river revealed itself as an outlet to the
  Atlantic Ocean and so the lake levels dropped to
  their current levels.

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Great Lakes Geology

• Both molten lava and glaciers shaped the
  shorelines and inland lands of the great lakes.
• The giant columns of the palisades are an example
  of solidified lava.
• The northwestern section of lake superior is
  known as Isle Royale National Park and is a prime
  example of the differences between the molten
  lava landscape and the glacier landscape.

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Great Lakes Geology

• The Isle Royales southern shoreline is made up
  of reddish sedimentary rocks deposited during a
  long pause in the retreating of the last
  glacier from Isle Royale, approximately 11,000
  years ago.
• The shores are flat similar to those of sandy
  beaches in many tropical areas.

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Great Lakes Geology

• The northern shoreline of the Isle Royale is
  composed of rocky bluffs that are a prime example
  of the cutting of the glaciers through the earths
  crust.

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Destructive Erosion

• A current problem with many great lakes
  shorelines is erosion.
• In the picture to the left is a picture of a
  house that has fallen into the water as a result
  of the earth below the house being eroded away by
  the continual beating of the waves on the loose
  shoreline.

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Beach Erosion

• Beach erosion is also a problem that many great
  lakes shorelines have.
• Beaches are very important to the ecology of the
  lakes.
• The great lakes environment depends greatly on
  the beach shoreline and would be dramatically
  different without them.

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Transportation Erosion

• Another type of erosion that has caused many
  problems is that to roadways along the shorelines
  of many of the great lakes.
• To the left is a picture of a roadway that has
  collapsed due to erosion from underneath the
  pavement.

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References

• http//www.great-lakes.net/teach/
• http//www.lre.usace.army.mil/
• http//www.great-lakes.net/
• http//www.glsc.org/
• http//www.epa.gov/glnpo/atlas/
• http//www.michigan.gov/deq/0,1607,7-135-3311_4112
  _4233-9336--,00.html
• http//www.uwgb.edu/dutchs/glkhist/glkhist0.htm
• http//geology.about.com/od/lakes/