THEORY OF PLATE TECTONICS

1. THEORY OF PLATE TECTONICS

2. PLATE TECTONICS • A. Defined: Earth’s crust and part of the upper mantle are broken into sections called lithospheric plates. These plates move on a plasticlike layer of the mantle called the asthenosphere.

3. PLATE TECTONICS • In the 1960’s, scientists developed a new theory that combined continental drift and seafloor spreading. • This new theory was the Theory of Plate Tectonics

4. Review/Summarize • Student A will turn to Student B and summarize the proof that Wegener had for continental drift. You have one minute. • Student B will turn to Student A and summarize why Wegener’s hypothesis was not accepted as a theory.

5. Outline for Graphic Organizer • I. Plate Tectonics Theory • A. Definition • B. Mapping of the Ocean Floor using • Sonar • 1. Longest Mountain Range in World • 2. Mid-Atlantic Ocean Ridge • C. Seafloor Spreading Proof • 1. Rock Ages • 2. Magnetic Pole Reversals

6. Proof of Plate Tectonics • During World War I, sound waves were introduced by German Scientists to detect submarines. • During the 1940’s and 1950’s, scientist began using B. sound waves on moving ships to map large areas of the ocean floor in detail. Sound waves echo off the ocean bottom—the longer the sound waves take to return to the ship, the deeper the water is. 1

7. Findings B.1.The ocean floor is covered with mountain ranges, B.2. the most famous is the Mid-Atlantic Ocean Range. This mountain range was formed through C. sea-floor spreading. Hot, less dense molten rock beneath the Earth’s crust rises toward the surface at the mid-oceanic ridges. It then flows sideways, carrying the seafloor away from the ridge in both directions. 12 We will learn more about sea-floor spreading when we study divergent boundaries.

8. Other Proof • In the 1960’s, scientists began gathering information about the rocks on the seafloor by drilling for rocks and mapping the ocean floor on board the research ship, Glomar Challenger.

9. GLOMAR Findings • One of the major findings of the research ship, Glomar Challenger, C.1.was that the rocks close to the mid-oceanic ridges were very young in age. They also found that the farther away from the ridge the rock was located, the older its age. • This was more proof of sea-floor spreading.

10. Let’s Summarize • What is the basis for the Theory of Plate Tectonics? • What did scientists use to map the bottom of the sea floor? • What did scientists find on the bottom of the sea floor? • What did they find out created these special features in the above question?

11. Even More Proof for Seafloor Spreading • While drilling core samples off the seafloor scientists also noticed the C.2. magnetic alignment of the iron filled basalt reversed on a regular basis. Huh? • Magnetic Pole Reversal

12. Pole Reversals • Now that we’ve read about this amazing process, let’s look at some animations to help us understand this more clearly. • 1234567

13. For 2012-13 • Revise graphic organizer and revise powerpoint to point. • Change summarizing questions into activotes. • Add summarizing questions at the end.

14. Conclusion • Let’s summarize what we have learned. • I. Plate Tectonics Theory • A. Definition • B. Mapping of the Ocean Floor using • Sonar • Longest Mountain Range in World • Mid-Atlantic Ocean Ridge • C. Seafloor Spreading Proof • 1. Rock Ages • 2. Magnetic Pole Reversals