1. Plate Tectonics Earth’s Interior Convection and the Mantle Drifting Continents Sea-Floor Spreading The Theory of Plate Tectonics Table of Contents

2. Plate Tectonics - Earth’s Interior Exploring Inside the Earth Geologists have used two main types of evidence to learn about Earth’s interior: direct evidence from rock samples and indirect evidence from seismic waves.

3. Plate Tectonics The Crust The crust is a layer of solid rock that includes both dry land and the ocean floor. - Earth’s Interior

4. Plate Tectonics The Mantle Earth’s mantle is made up of rock that is very hot, but solid. Scientists divide the mantle into layers based on the physical characteristics of those layers. - Earth’s Interior

5. Plate Tectonics Temperature Inside the Earth The graph shows how temperatures change between Earth’s surface and the bottom of the mantle. On this graph the temperature at the Earth’s surface is 0 o C. Study the graph carefully and then answer the questions. - Earth’s Interior

6. Plate Tectonics Temperature Inside the Earth The depth increases. Reading Graphs: As you move from left to right on the x-axis, how does depth inside the Earth change? - Earth’s Interior

7. Plate Tectonics Temperature Inside the Earth About 1,600 o C Estimating: What is the temperature at the boundary between the lithosphere and the asthenosphere? - Earth’s Interior

8. Plate Tectonics Temperature Inside the Earth About 3,200 o C Estimating: What is the temperature at the boundary between the lower mantle and the core? - Earth’s Interior

9. Plate Tectonics Temperature Inside the Earth It generally increases with depth. Interpreting Data: How does temperature change with depth in Earth’s interior? - Earth’s Interior

10. Plate Tectonics The Core The core is made mostly of the metals iron and nickel. It consists of two parts–a liquid outer core and a solid inner core. - Earth’s Interior

11. Plate Tectonics What You Know What You Learned Using Prior Knowledge Before you read, look at the section headings and visuals to see what this section is about. Then write what you know about Earth’s interior in a graphic organizer like the one below. As you read, write what you learn. 1.Earth’s crust is made of rock. 2.Earth is very hot near the center. 3.Dry land is part of the crust. 4.The mantle is very hot. 5.The core contains iron. 1.Geologists use seismic waves to study Earth’s interior. 2.Radioactive substances heat the interior of Earth. 3.The crust is thickest under high mountains. 4.The mantle is solid. 5.Movements in the outer core create Earth’s magnetic field. - Earth’s Interior

12. Plate Tectonics Links on the Structure of Earth Click the SciLinks button for links on the structure of Earth. - Earth’s Interior

13. Plate Tectonics Types of Heat Transfer There are three types of heat transfer: radiation, conduction, and convection. - Convection and the Mantle

14. Plate Tectonics Convection Currents Heating and cooling of the fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. - Convection and the Mantle

15. Plate Tectonics Convection Currents in Earth Heat from the core and the mantle itself causes convection currents in the mantle. - Convection and the Mantle

16. Plate Tectonics Mantle Convection Click the Video button to watch a movie about mantle convections. - Convection and the Mantle

17. Plate Tectonics Continental Drift Wegener’s hypothesis was that all the continents were once joined together in a single landmass. - Drifting Continents

18. Plate Tectonics Evidence for Continental Drift Fossils and rocks found on different continents provide evidence that Earth’s landmasses once were joined together in the supercontinent Pangaea. - Drifting Continents

19. Plate Tectonics Evidence for Continental Drift Fossils and rocks found on different continents provide evidence that Earth’s landmasses once were joined together in the supercontinent Pangaea. - Drifting Continents

20. Plate Tectonics Mid-Ocean Ridges The East Pacific Rise is just one of the many mid-ocean ridges that wind beneath Earth’s oceans. - Sea-Floor Spreading

21. Plate Tectonics What Is Sea-Floor Spreading? In sea-floor spreading, the sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added. As a result, the ocean floors move like conveyor belts, carrying the continents along with them. - Sea-Floor Spreading

22. Plate Tectonics Evidence for Sea-Floor Spreading Several types of evidence supported Hess’s theory of sea- floor spreading: eruptions of molten material, magnetic stripes in the rock of the ocean floor, and the ages of the rocks themselves. - Sea-Floor Spreading

23. Plate Tectonics Subduction at Trenches In a process taking tens of millions of years, part of the ocean floor sinks back into the mantle through deep-ocean trenches. - Sea-Floor Spreading

24. Plate Tectonics Growing an Ocean Because of sea-floor spreading, the distance between Europe and North America is increasing by a few centimeters per year. - Sea-Floor Spreading

25. Plate Tectonics Sea-Floor Spreading Click the Video button to watch a movie about sea-floor spreading. - Sea-Floor Spreading

26. Plate Tectonics How Plates Move The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates. - The Theory of Plate Tectonics

27. Plate Tectonics Plate Boundaries - The Theory of Plate Tectonics There are three kinds of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries. A different type of plate movement occurs along each type of boundary.

28. Plate Tectonics Continental Drift It has taken the continents about 225 million years since the breakup of Pangaea to move to their present locations. - The Theory of Plate Tectonics

29. Plate Tectonics Building Vocabulary A definition states the meaning of a word or phrase by telling about its most important feature or function. After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a definition of each Key Term in your own words. Key Terms:Examples: - The Theory of Plate Tectonics plateThe lithosphere is broken into separate sections called plates. scientific theoryA scientific theory is a well-tested concept that explains a wide range of observations. plate tectonicsThe theory of plate tectonics states that pieces of Earth’s lithosphere are in slow, constant motion, driven by convection currents in the mantle. faultFaults are breaks in Earth’s crust where rocks have slipped past each other. Key Terms:Examples: divergent boundary rift valley convergent boundary transform boundary The place where two plates move apart, or diverge, is called a divergent boundary. A deep valley called a rift valley forms along the divergent boundary. The place where two plates come together, or converge, is called a convergent boundary. A transform boundary is a place where two plates slip past each other, moving in opposite directions.

30. Plate Tectonics Type of Plate Boundary Type of MotionEffect on Crust Feature(s) Formed Plates slide past each other. Subduction or mountain building Mid-ocean ridge, ocean floor Graphic Organizer Transform boundary Crust is sheared. Strike-slip fault Convergent boundary Plates move together. Mountains, volcanoes Divergent boundary Plates move apart. Crust pulled apart by tension forces.