Transcript Plate Tectonics

Plate Tectonics
Earth Science Essentials
North Farmington High School
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What is Plate Tectonics
• Crust of the Earth FLOATS on top of the mantle.
• Crust is broken into slabs (plates) that MOVE, slide,
collide, and spread apart.
• Cause of earthquakes, mountains, and volcanoes.
Click HERE to
see crust of the
Earth
FLOATING on
the mantle.
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Continental Drift
• In 1912, Alfred Wegener
first proposed that the
continents are moving.
• He claimed the “continents
are drifting like rafts in the
water.” He called it
Continental Drift.
• Initially all the continents
were connected in 1 super
continent call Pangaea
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Evidence for plate movement
• Wegener collected 6
major pieces of evidence
that the plates were
moving.
• He failed to convince the
geological society at the
time because he could
not explain WHY the
plates were moving.
Plate tectonics was not
fully accepted until the
1970s.
SAD
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1. Shorelines
• Shorelines fit like pieces of a puzzle
• Click HERE to watch an animation of the
breakup of Pangaea
PANGAEA
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2. Fossils of extinct species
• Fossils of now extinct animals and plants were
found on BOTH sides of the Atlantic.
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3. Tropical Fossils
• Fossils of tropical plants found in
extremely cold climates or vice-versa.
• Michigan itself has tropical fossils! During
Pangaea we were MUCH closer to the
equator!
MICHIGAN
Petoskey Stone
(fossil) was a
tropical coral!
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4. Fossils and evolution
• Fossils of species on
one side of the Atlantic
found on the other
side.
• Today the species
appear much different
from each other due to
evolution BUT they
have a common
ancestor
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5. Mountains line up
• Mountain ranges
from opposing sides
of the Atlantic match
in age and rock type.
• Ex: The N. American
Appalachian
Mountains line up
with the Atlas
mountains of Africa!!!
Appalachian Mtns
– Both ranges are
roughly 200 million
years old. The same
time Pangaea split
apart.
Atlas Mtns
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6. Glacier Scratches
There have been MANY
ice ages. One occurred Glacier scratches do NOT
during Pangaea. The
make sense. Seem
haphazard or random.
weight of the ice
SCRATCHES the bedrock
below leaving scars called
striations.
Scratches found on many
continents don’t line up or
As
make sense UNTIL you
Pangaea,
put the continents
the glacier
scratches
together as Pangaea.
line up and
make
sense.
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How did Plate Tectonics become a
theory?
• Earth is a giant magnet.
• Magnetic north, currently near the North Pole,
REVERSES and is found near the South pole.
• This occurs about once every million years.
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Paleomagnetism
• The history of Earth’s magnetic field is
recorded in the crust of the oceans.
• Ocean crust contains lots of iron (mafic)
that gets magnetized AND points to
magnetic NORTH.
• Watch the paleomagnetism animation,
click HERE
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