Theory of Plate Tectonics

1. Chapter 3 Lesson 3 Theory of Plate Tectonics

2. What Is The Theory of Plate Tectonics? • Key Answer: The theory of plate tectonics states that Earth’s plates are in slow motion driven by convection currents in the mantle. • Explains the formation, movement, & subduction of Earth’s plates • How is that different from Wegener’s Theory of Continental Drift?

3. Theory of Plate Tectonics • Plate- A section of the lithosphere that slowly moves over the athenosphere; carrying pieces of continental & oceanic crust. • Earth’s plates meet at boundaries • At each boundary the plate can move 1 of 3 ways. • Diverge • Converge • Transform

4. Vocab • Divergent Boundary- plates move apart • Convergent Boundary – plates come together • Transform boundary- plates slip past each other • Plate Tectonics- KEY ANSWER

5. Mantle, Convection, & Plate Movements • Earth’s plates move because they are on top of convection currents in the mantle. • During subduction, gravity pulls denser plate edges toward the mantle • The rest of the plate also moves

6. Plate Motions Over Time • Measured by satellites • 1-12 cm per year (average) • As plates move they change Earth’s surface producing Earthquakes, volcanoes, mt. ranges, & deep ocean trenches

7. Plate Boundaries • Faults- breaks in Earth’s crust where rocks have slipped past each other – form along boundaries

8. Divergent Boundaries • Most occur along mid-ocean ridges • Rift Valley- deep valley where Earth’s crust diverges on land

9. Convergent Boundaries • Where 2 plates collide & the density determines who will come out on top • So who comes out on top? • As the denser rock subducts, it create a trench • Magma can then climb the mountain to form a volcano • 2 ocean crusts collide = trench • 2 continental crusts collide = Mountains • 1 of each collides = Volcanoes

10. Transform Boundaries • As 2 plates slide apart it can create an Earthquake