Plate Tectonic Theory

1. Plate Tectonic Theory TXT pg. 106 Chapter 3…section 5

2. Definitions to know • Plates: Sections of the lithosphere that are fitted together along cracks • Scientific Theory: Well tested concept that explains observations

3. Theory • Pieces of the earth’s lithosphare are in slow, constant motion, driven by convection currents in the mantle. • Explains the formation, movement, and subduction of Earth’s plates.

4. HOW DO THEY MOVE??? • Movements in the mantle cause the plate to move • Gravity pulls one side of the plate down by subduction, causing the rest of the plate to move forward • As they move, the collide, pull apart, or grind with other plates • This causes the formation of volcanoes, mountain ranges, and deep ocean trenches

5. Plate Boundaries • Extend into the lithosphere • Faults: (Form along the boundaires)Break in the earth’s crust where rocks have slipped past each other • 3 Kinds: • Divergent • Convergent • Transform

6. Divergent Boundaries • Plates move apart (Diverge) • Most occur on mid ocean ridges • Can occur on land Causing a Rift valley (deep valley where the plates slide apart • Example: Death Valley

7. Convergent Boundaries • Where 2 plates come together • When they converge, they will collide. Density decides which one gets forced up and which one down….More dense plate sinks under other past • Oceanic Crust is more dense than continental crust • When continental crust collides, neither is more dense, so mountain ranges form.

8. Transform Boundary • 2 plates slide past each other in opposite directions (Like rubbing your hands together) • Crust is not created or destroyed here • Earthquakes happen at transform boundaries

9. Pangea Proof • By proving that the earth’s plates are moving, scientists were able to show that there was once a pangea and that the continents broke apart and moved to their current position. • Pg. 110 shows this in motion and the time span