Transcript The Great Lakes

The Great Lakes
Brandon Dunn, Kate Thometz, Vince Amicon
Huron
Ontario
Michigan
Erie
Superior
THE GREAT LAKES
• Largest group of fresh
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water lakes worldwide
Borders United States
and Canada
Used today as major
source of
transportation
GEOLOGIC HISTORY
• Formed as a result of the Ice Age 10,000 years
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ago
The Lauren tide Glaciation melted with rising
temperatures and dug a whole in the Earth’s
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
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.
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
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.
Background
• The Great Lakes is a group of five
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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.
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.
Rock Formations
• As the glaciers receded their
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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.
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.
Great Lakes Geology
• The Isle Royale’s 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.
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.
Destructive Erosion
• A current problem with
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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.
Beach Erosion
• Beach erosion is also a
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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.
Transportation Erosion
• Another type of erosion
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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.
References
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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/0,1
607,7-135-3311_4112_42339336--,00.html
• http://www.uwgb.edu/dutchs/glkh
ist/glkhist0.htm
• http://geology.about.com/od/lakes
/