Plate Tectonics

Theory that helps explain most geologic processes. Theory that helps explain most geologic processes. Earth’s shell is made up of approximately 20 plates (made up of continents and oceans) 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. 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 Alfred Wegener suggested all earth’s land masses collided 300 million years ago to form one supercontinent He named it PANGAEA. 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

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

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 Wegener could not explain what mechanism was powerful enough to move huge continents Scientist’s never believed him Scientist’s never believed him

J. Tuzo Wilson Wilson (Canadian) sparked new interest in continental drift theory. Wilson (Canadian) sparked new interest in continental drift theory. Now known as plate tectonics (includes more than just continents, also includes ocean plates) 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. Perhaps caused by uneven distribution of heat within the earth, causing convection currents.

Convection Currents

Plate Movements 1. Convergent Boundaries 2. Divergent Boundaries 3. Transform Boundaries

Convergent Plate

Convergent

Divergent Plate

Divergent

Transform