Sea Floor Spreading and Plate Tectonics

1. Sea Floor Spreading and Plate Tectonics Chapter 1.4 and 1.5

2. Ch. 1.4 Sea-Floor Spreading Mid-Ocean Ridge • longest chain of mountains in the world • all below the ocean • Scientists use SONAR to map them SONAR -a device that records echoes of sound waves History of Ocean Drilling

3. 2. Sea-floor spreading? • At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. Earth's Volcanic History

4. 3. Scientists found Evidence Molten Material found • as pillow-shaped rocks • hardened quickly

5. 3. Scientists found Evidence Magnetic patterns or stripes found in • Ocean floor rock • Reversals of Earth’s magnetic field

6. 3.3. Scientists found Evidence Drilling core samples • age of rock samples • The farther away from the mid-ocean ridge, the older the rocks Drilling for Cores Samples

7. 4. Subduction at Deep-Ocean Trenches • Subduction: a process where the ocean floor sinks beneath a deep-ocean trench and back into the mantle… over tens of millions of years. Sketch this picture

8. Subduction at Earth’s Oceans Drilling in the Arctic Ocean

9. Ch. 1.5 Theory of Plate Tectonics Plate Motion • Pieces of Earth’s lithosphere are in constant slow motion • Driven by convection currents in mantle • Theory of Plate Tectonics explains the • Formation • Movement • Subduction of Earth’s plates

10. Plate Boundaries • Plate boundaries are-where edges of lithosphere meet • Faults are- breaks in the crust, where rocks that slip past each other form at plate boundaries

11. 3 Types of Plate BoundariesTransform boundaries • Where 2 plates slip past each other

12. Plate boundariesDivergent boundaries • Where 2 plates move apart • A rift (deep) valley forms

13. 2. Plate boundaries Convergent • Where 2 plates come together or collide The plate density determines which plate goes under-subduction Where continental crusts collide-it forms mountains

14. Plate boundaries

15. Continent’s Slow Dance • 225million years ago, plates joined together- Pangaea • 180-200 mya Continents split apart, narrow seas become oceans • 135 mya Continents began to drift apart • 65 mya India a separate continent, Australia connected to Antarctica • Today continents look like puzzle pieces that once were together Take Aim At Climate Change