Plate Tectonics
Plate Tectonics



Theory that helps explain most
geologic processes.
Earth’s shell is made up of
approximately 20 plates (made up of
continents and oceans)
Plates moving over a weak layer of hot
rock.
Continental Drift


Alfred Wegener suggested all earth’s
land masses collided 300 million years
ago to form one supercontinent
He named it PANGAEA.
Pangaea
Wegener’s Proof
1.
He saw a jigsaw fit between South
America and Africa
2.
Fossils of the same plants and
animals on both continents.
Wegener’s Proof
Wegener’s Proof
3. Mountains of similar age and
structure on both sides of the Atlantic
Ocean
Wegener’s Proof
Wegener’s Proof
4. Ice sheets covered southern Africa,
India, Australia, and South America
300 million years ago.
Wegener’s Proof
Missing Proof


Wegener could not explain what
mechanism was powerful enough to
move huge continents
Scientist’s never believed him
J. Tuzo Wilson


Wilson (Canadian) sparked new
interest in continental drift theory.
Now known as plate tectonics
(includes more than just continents,
also includes ocean plates)
Plate Movements

Perhaps caused by uneven distribution
of heat within the earth, causing
convection currents.
Convection Currents
Convection Currents
Plate Movements
1.
2.
3.
Convergent Boundaries
Divergent Boundaries
Transform Boundaries
Convergent Plate
Convergent
Divergent Plate
Divergent
Transform