Plate TectonicsPlate Tectonics

Plate TectonicsPlate Tectonics

Theory that helps explain most Theory that helps explain most geologic processes.geologic processes.

Earth’s shell is made up of Earth’s shell is made up of approximately 20 plates (made approximately 20 plates (made up of continents and oceans)up of continents and oceans)

Plates moving over a weak layer Plates moving over a weak layer of hot rock.of hot rock.

Continental DriftContinental Drift

Alfred Wegener suggested all Alfred Wegener suggested all earth’s land masses collided 300 earth’s land masses collided 300 million years ago to form one million years ago to form one supercontinentsupercontinent

He named it PANGAEA.He named it PANGAEA.

Pangaea

Wegener’s ProofWegener’s Proof

1.1. He saw a jigsaw fit between He saw a jigsaw fit between South America and AfricaSouth America and Africa

2.2. Fossils of the same plants and Fossils of the same plants and animals on both continents.animals on both continents.

Wegener’s ProofWegener’s Proof

Wegener’s ProofWegener’s Proof

3. 3. Mountains of similar age and Mountains of similar age and structure on both sides of the structure on both sides of the Atlantic OceanAtlantic Ocean

Wegener’s ProofWegener’s Proof

Wegener’s ProofWegener’s Proof

4. Ice sheets covered southern 4. Ice sheets covered southern Africa, India, Australia, and South Africa, India, Australia, and South America 300 million years ago.America 300 million years ago.

Wegener’s ProofWegener’s Proof

Missing ProofMissing Proof

Wegener could not explain what Wegener could not explain what mechanism was powerful enough mechanism was powerful enough to move huge continentsto move huge continents

Scientist’s never believed himScientist’s never believed him

J. Tuzo WilsonJ. Tuzo Wilson

Wilson (Canadian) sparked new Wilson (Canadian) sparked new interest in continental drift interest in continental drift theory.theory.

Now known as plate tectonics Now known as plate tectonics (includes more than just (includes more than just continents, also includes ocean continents, also includes ocean plates)plates)

Plate MovementsPlate Movements

Perhaps caused by uneven Perhaps caused by uneven distribution of heat within the distribution of heat within the earth, causing convection earth, causing convection currents.currents.

Convection CurrentsConvection Currents

Convection CurrentsConvection Currents

Plate MovementsPlate Movements

1.1. Convergent BoundariesConvergent Boundaries

2.2. Divergent BoundariesDivergent Boundaries

3.3. Transform BoundariesTransform Boundaries

Convergent PlateConvergent Plate

ConvergentConvergent

Divergent PlateDivergent Plate

DivergentDivergent

TransformTransform