The Glacial Features of Marthas Vineyard Part One

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The Glacial Features of Marthas Vineyard - Part
One
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Questions to answer

• How did the ice and water from the glacier form
  the Vineyard?
• Why is the Vineyard shaped like it is?
• Why are some areas hilly and other areas so flat?
• Why are some parts sandy and other areas full of
  rocks and boulders?
• How did the freshwater ponds and the saltwater
  ponds form?
• When did the Vineyard first form, and how has it
  changed since then?

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Think about the variety in our landscape.That is
why the Island is so beautiful.
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For a small island, it is very diverse.And
perhaps that is why the Island is so popular.
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So how did it get that way? And what did the
Pleistocene Ice Age have to do with it?
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KEEP IN MIND

• Huge continental glaciers can reshape the land
  beneath them and in front of them, completing
  scraping away the land, while carving new
  landscapes.
• And they can carry this material (soil, rocks,
  etc. . .) for hundreds of miles, depositing it
  into a variety of new landscapes.

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LETS GO BACK IN TIME

• Imagine being on the Earth about 18,000 years
  ago, at peak glaciation of the Wisconsinan Stage
  of the Pleistocene Ice Age.
• What would it be like? What would it look like?

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Probably something like this (Greenland today).
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And this (also on Greenland).
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Here is what a map of North America would have
looked like then.
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The Ice Sheets

• It is important to remember that the great ice
  sheets - even at their largest and not growing
  bigger - actually flowed.
• Glacial ice flows very slowly, but it can
  sometimes surge rapidly.
• As glacial ice flows, it scrapes and plucks and
  deposits and reshapes the land underneath it, and
  even ahead of it.
• The direction of the flow is important to note.

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• There were actually three main ice sheets in
  North America.
• Notice the direction of the ice flow.
• Why is the direction always away from the center
  of the ice sheets?

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Glacial till

• Term for anything carried by glaciers.
• Rocks, gravel, sand, silt, clay.
• Our till was carried from places as far away as
  New Hampshire, Vermont, even Canada.
• Also called glacial drift.
• Glaciers, even smaller mountain glaciers, can
  carry hundreds or thousands of CUBIC MILES of
  till.

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Glacial ice can be loaded with till.
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Now imagine flying over what will someday be
called New England, including Marthas Vineyard.
Remember what happened to sea level. Look where
the coast was then!
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This is what it probably looked like then.(This
shot is from Greenland today.)
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The Edge of the Ice

• Actually made of many lobes of ice.
• Ice was loaded with till. Till especially built
  up along edges of the ice because of the ice
  flow.
• Tremendous winds blowing off the ice.
• Glacial meltwater runs from the edge as ice is
  constantly melting, often forming streams that
  criss-cross.
• The land just beyond the edge is frigid cold,
  barren, harsh (tundra-like conditions).
• We see these conditions in Greenland today.

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The top of a glacial ice sheet.(This shot is
also from Greenland.)
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There were three main lobes of ice that
contributed to forming Cape Cod and the Islands.
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Notice the direction of the ice flow. Notice the
shape of the ice lobes, and the shape of the Cape
and Islands. Notice where the ice stopped
(twice). Is this a coincidence?
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Summary

• The Pleistocene Ice Age reshaped much of North
  America forever.
• The Pleistocene Ice Age is also responsible for
  the formation of the Cape and Islands
• Both glacial ice and glacial meltwater can change
  the landscape, but in different ways.
• Till is any material carried by glacial ice.
• Glacial ice flows very slowly as it grows. We
  can tell the direction of the flow today.
• Glacial ice can also melt back, leaving deposits.
• The edges of these huge ice sheets were
  especially full of till.
• The edges also are where the meltwater occurred
  mostly.
• We can go to Greenland today to study the best
  example of how a huge continental glacier looks
  and behaves.