1. Sea Floor Spreading
Chapter 4.4

2. What is the mid-ocean ridge?
What do we use to map the mid-ocean ridge?
The mid-ocean ridge is the longest chain of mountains in the world.
The mid-ocean ridge is mapped using Sonar.

4. What idea did Harry Hess propose?
Harry Hess proposed that ocean floors move like conveyer belts, carrying the continents along with them. This movement begins at the mid-ocean ridge called Sea Floor spreading.

5. How does this movement at the mid-ocean ridge begin?
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.

7. Three Types of Evidences:
What types of evidence support the theory of sea-floor spreading?
Three Types of Evidences:
Evidence from Molten Material

8. How does magnetic stripes support the theory of Sea floor spreading?
2. Evidence from Magnetic Stripes

11. Evidence of Sea floor spreading video
3. Evidence from Drilling Samples Youngest rock was found in the center and older further away.

12. Older
Younger

13. What is subduction?
Subduction is the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle.
another animation of plate tectonics
.subduction clip

14. Subduction

15. What is created where subduction occurs?
The ocean floor plunges into deep underwater canyons called deep-ocean trenches.
Deep Ocean Trench

16. How does this help explain Wagner’s idea of continental drift?

17. Why doesn’t the ocean floor keep getting wider?
The Pacific Ocean is getting smaller and the Atlantic Ocean is getting bigger.
Bill Nye sea floor spreading video