The document discusses plate tectonics and describes how convection currents in the asthenosphere cause tectonic plates to move horizontally at the surface. There are three types of plate boundaries: divergent boundaries where plates move apart and new seafloor is created, convergent boundaries where plates move together and seafloor is destroyed forming trenches and volcanic islands, and transform boundaries where plates slide past each other forming faults. Examples given are the San Andreas fault and the Ring of Fire around the Pacific plate.

1. 12. Plate Tectonics

4. Mechanism of Plate Tectonics
• Material in asthenosphere heats and rises
• When it cools it moves horizontally and sinks
• This movement of material is called
convection cells

5. The Three Types of Plate Boundaries

7. Divergent
-Rift Zone
-Plates moving apart
-Sea Floor created
-Mid Ocean Ridges

8. Convergent
-Subduction Zones
-Plates moving toward
each other
-Seafloor destroyed
-Creates trenches &
Volcanic Island Arcs

9. Transform
• Plates move
past each
other
• Faults are
formed

10. Example of Transform: San
Andreas

11. Ring of Fire
• Around Pacific Ocean
• Greatest quantity of earthquakes/volcanoes
• Ring (outer edge of) Pacific Plate is full of faults