Download The Origin of Continents and Oceans

PLATE TECTONICS,
EARTHQUAKES, AND THE
STRUCTURE OF THE EARTH
GOALS FOR THE LECTURE
•
Students will write and discuss various ideas
related to the physical structure of the Earth
(9C, 10A, 10B, 10C, 10E, 10F)
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Students will write and discuss ideas related to
plate tectonics, as well as follow its
progression through history(10D)
WHY DOES THE EARTH LOOK
LIKE THIS?
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Where did the tectonic plates come from?
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They came from the ancient land masses the used to
cover the Earth
HISTORY
•
Has the Earth always looked like this?
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What did the Earth look like in the past?
HISTORY
•
What name do we give this place?
•
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When was this?
•
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Pangea
200 million years ago (mya)
Before there was Pangea, the Earth looked
even less like it does today
HISTORY
• About 160 mya, Pangea began to break apart.
• Laurasia and Gondwanaland were the dominant
land features.
HISTORY
•
About 120 mya, Laurasia and Gondwanaland
began to break apart.
•
Continents we might recognize were the
result.
HISTORY
•
80 mya, Madagascar breaks off from India as
India begins its race across the Indian Ocean.
HISTORY
•
40 mya, Inland seas in the North American
Plate and Asian plates drained and India
began to push up the Himalayan mountains.
TODAY
FOSSIL EVIDENCE
•
Organisms have left fossil evidence of their
existence on continents across oceans.
•
Originally thought to be caused by organisms
traveling across the ocean on “Rafts.”
FOSSIL EVIDENCE
•
Other theories suggested organisms crossed
over land bridges that were once exposed.
FOSSIL EVIDENCE
•
A 3rd theory surfaced known as Island
stepping stones.
EVIDENCE THAT THIS IS WHAT
REALLY HAPPENED…
CONTINENTAL DRIFT
•
Alfred Wegener publishes The Origin of
Continents and Oceans in 1915.
•
Proposes that the continents were once all
part of a large landmass called Pangea, and
then drifted apart.
CONTINENTAL DRIFT
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This idea matured into our current theories of
Plate Tectonics
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The surface of the earth is divided into about
20 plates.
PLATE TECTONICS
•
All plates contain both continental and
oceanic crust.
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This is a major departure from continental drift.
THE THEORY
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Plates are rigid structures and will always
move as a distinct unit.
•
The distance between two points on a tectonic plate
will always be the same
LITHOSPHERE
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The layer of solid rock that surrounds the Earth
and a thin layer of molten rock beneath it.
ASTHENOSPHERE
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The molten rock beneath the lithosphere.
WHERE DO THINGS
CHANGE?
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At the boundaries between plates.
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3 categories
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Divergent
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Convergent
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Transform
DIVERGENT
WAIT NO…
DIVERGENT BOUNDARIES
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Occur at oceanic spreading centers, typically
called “Mid-Ocean Ridges”
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2 “Plates” are being pulled apart by magma
from underneath that is pushing upwards
•
Process known as Seafloor Spreading
CONVERGENT BOUNDARIES
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3 classifications of Convergent Boundaries
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Oceanic-Continental
Oceanic-Oceanic
Continental-Continental
CONVERGENT BOUNDARIES
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Subduction Zone(vocabulary)- the place
where one tectonic plate rides up over
another and causes it to be pushed down
and recycled (melted)
CONVERGENT BOUNDARIES
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Oceanic-Continental
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Result in the formation of Volcanic Arcs along the
boundary
CONVERGENT BOUNDARIES
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Oceanic-Oceanic
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Result in the formation of Island Arcs
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Chains of volcanic islands that form along oceanic
plate boundaries
CONVERGENT BOUNDARIES
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Oceanic-Oceanic boundaries will also result in
the formation of Trenches
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These are places where the ocean is deeper
than the surrounding area due to subduction.
CONVERGENT BOUNDARIES
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Continental-Continental
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Result in the formation of mountain ranges
made from deformed (squeezed) native rock
CONVERGENT BOUNDARIES
TRANSFORM BOUNDARIES
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Plates move in opposing directions on either
side of the boundary.