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Where Are We Going?
Plate Tectonics and the Evidence
Behind the Theory
Plate Tectonics and the Evidence
Behind the Theory
As any good scientist would do, we'll begin
by asking a few questions:
– How did the mountains get there?
– What caused the huge tsunami?
– What causes some volcanoes to erupt while
others lay dormant?
These questions arise when we look around
us and question what's going on.
What Happened Here?
For example: Look at
these pictures.
These pictures were
taken near the San
Andreas Fault. What
made the rocks in the
hillsides curve
like that?
And Here?
Continental Drift
This is caused by
movement of the Earth's
tectonic plates. The idea
that the Earth has plates of
material that are actively
moving around and
changing the shape of our
planet was not articulated
until 1912 by Alfred
Wegener in what is now
known as the Theory of
Continental Drift.
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Drifting???
Wegener believed that these plates
were once part of one giant
supercontinent, Pangaea, which
broke apart and allowed the
continents to “drift.” Since then
it has been determined that the
continents are not just “drifting”
but rather moving apart due to
plate tectonics. Wegener’s
theory was, however,
instrumental in paving the way
for the Theory of Plate
Tectonics.
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Plate Tectonics
• The Theory of Plate Tectonics, as proposed
by William Ewing and Harry Hess, states
that the Earth’s outermost layer is
fragmented into a dozen or more large and
small plates that are moving relative to one
another as they ride above the hotter, more
mobile material below. (This Dynamic
Earth, USGS, www.usgs.gov)
The Earth’s Plates
What Evidence Do You Have?
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In this lesson, we will look at the existing evidence for this theory. The
evidence includes:
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Fit of the Continents
Fossils
Rocks
Paleoclimatic Patterns
Paleomagnetic Patterns
Sea Floor Topography