The Great Lakes

1
The Great Lakes

• A Presentation made by Benjamin Ashraf
• IB 447 - Spring 2006

2
Areas of Focus

• The Great Lake Region During the Ice Age.
• The Formation of the Great Lakes
• The Drainage of the Lakes
• The Modern Lakes

3
The Great Lakes - Ice Age
4
The Pleistocene Epoch

• Occurred on earth from about 1.6 million to
  10,000 years ago.
• During this time the majority of the northern
  hemisphere was covered in ice with average
  temperatures around 15 degrees colder than the
  average today.

5
The Pleistocene Epoch Cont.

• This epoch was also marked by at least 4 separate
  incidences in which glaciers advanced and
  retreated from Canada to as far down as Chicago.
• Of these 4 glaciers the one we will be most
  concerned with is the final one known as the
  Laurentide Glacier.

6
Laurentide Glacier

• Began to form around 100,000 years ago.
• At its peak around 18,000 years ago the
  Laurentide covered almost all of Canada and
  extended as far down as Chicago.
• The Glacier was also estimated around 4km thick.

7
Laurentide cont.

• As the glacier advanced across N. America,
  several mountains and hills that it came across
  was subsequently destroyed.
• This process known as glacial erosion is
  responsible for the majority of the modern day
  valleys across the United States and Canada.

8
End of the Laurentide

• Yet around 14,000 years ago the Laurentide
  glacier began to recede due the rising
  temperature of the earth.
• This meltdown is responsible for the formation
  of what would become the Great Lakes.

9
Unfortunately this brought some hardships to our
heroes as well.
10
Early Lakes - Formation

• As mentioned before as the Laurentide Glacier
  advanced across North America several mountains
  and hills were subsequently destroyed by the
  process of glacial erosion.
• Some of these destroyed land bodies left massive
  craters within the crust of the earth.

11
Early Lake Formation cont.

• And as the Laurentide receded and began to melt,
  these craters were subsequently filled with what
  is known as meltwater from the glacier.

12
Early Lakes - Characteristics of

• These early Lakes were by all accounts far larger
  than there modern day counterparts.
• As well these lakes also had different drainage
  routes than they had today.

13
Early Lakes Characteristics Cont.

• Yet around 7,000 years ago the recession of the
  Laurentide Glacier revealed what became known as
  the St. Lawrence River Valley which emptied into
  the Atlantic Ocean.
• Eventually the Lakes water levels dropped to
  levels similar to the lakes of today.

14
Great Lakes - Drainage of

• As previously mentioned there were several
  different avenues for drainage for the early
  lakes before the emergence of the St. Lawrence
  River valley around 7,000 years ago.

15
Drainage Cont.

• For instance, the two ancestral Great Lakes known
  as Lake Maumee and Lake Chicago had multiple
  outlets depending upon how far the ice had
  receded at that time.
• For instance Lake Maumee, which became Lake Erie,
  initially emptied into the Mississippi River but
  around the time of 7,000 years ago was emptying
  in Lake Ontario and then to the Atlantic Ocean.

16
Drainage Cont.

• For the upper lakes one is able to see a similar
  instance of different drainage outlets depending
  upon the location of the Laurentide ice sheet.
• Around 13,000 years ago the upper lakes emptied
  chiefly into Lake Chicago much like Lake Maumee
  did.

17
Drainage Cont.

• Yet with the final recession of the ice around
  11,000 years ago the formation of Lake Algonquin
  both Huron and Michigan became connected and
  started to drain into the newly formed Lake
  Ontario.
• Eventually through various stages of Crustal
  Rebound the main area of drainage also became the
  St Lawrence for the upper Lakes as well.

18
(No Transcript)
19
The Modern Lakes

• After the St. Lawrence became the main avenue of
  drainage for the lakes they have pretty much
  remained the same with minor changes in both
  water levels and the shifting of shore lines.
• Thus concludes my presentation.

20
Resources Used

• 1) Formation of the Great Lakes
• www.emporia.edu/earthsci/ student/damery1/gl_form
  .html.
• 2) Great Lakes Formation
• techalive.mtu.edu/meec/module/
• GreatLakesPastandPresent.htm