The Theory of Plate Tectonics

1. The Theory of Plate Tectonics Pgs 99 - 102

2. Plate tectonics • The theory that the Earth’s lithosphere is divided into tectonic plates that move around on top of the asthenosphere • It combines the principals of continental drift and seafloor spreading.

3. Possible Causes of Plate Motion • An incredible amount of energy is needed to move the massive tectonic plates. • Where does that energy come from? • Heat and gravity affect three possible answers.

4. Driving forces of Plate Tectonics • Ridge push – the process by which an oceanic plate slides down the lithosphere-asthenosphere boundary. • Slab Pull – the edge of the oceanic plate sinks and pulls the rest of the tectonic plate with it because the oceanic lithosphere is denser than the asthenosphere.

5. More Driving forces • Convection – hot material from deep within the Earth rises while cooler material near the surface sinks. When warmer material cools, it becomes denser and begins to sink back down. The motion of convecting mantle material drags tectonic plates sideways.

6. Plate Boundaries • All tectonic plates have boundaries with other plates. • The boundaries are categorized on how they collide separate or slide past each other

7. Convergent Boundaries • This is when two plates push into one another. • Continental/Continental – When colliding the plates push continental crust upward to form mountains. • Continental/Oceanic – When colliding the oceanic plate slides under the continental plate into the asthenosphere creating a subduction zone. • Oceanic/Oceanic – when colliding the one oceanic plate slides past another and can form volcanoes.

8. Divergent Boundaries • This is when two tectonic plates move away from each other. • As they move apart, magma rises to fill the gap and cools to form new oceanic lithosphere.

9. Transform Boundaries • This is when two tectonic plates slide past each other horizontally. • When the slide past, they tend to grind and jerk to produce earthquakes. • The San Andreas fault is an example of a transform boundary.

10. GPS (Global Positioning System) • GPS can be used to measure the rate at which tectonic plates move. • GPS ground stations send radio signal to GPS satellites and are constantly measuring their position. • Over time the plates move and GPS can track the rate at which they move a certain distance. • With this information scientists can estimate how far tectonic plates have moved and the direction in which they will move.