1. PLATE TECTONICS

2. What is plate tectonics?
Theory based on the idea that the lithosphere is composed of a # of segments (plates) that move independently of one another, at varying speeds over Earth’s surface.
Based on the principle of buoyancy – that something less dense (wood) floats on something denser (water).

3. EARTH’S INNER FURNACE
Source:

4. Isostacy
Theory which holds that the Earth’s crust floats on the denser layers beneath, like a boat floats on water.
Where the load is greater, the crust rides lower in the asthenosphere.
Where the load is lighter, the crust rides higher.

7. Divergent Plate Boundaries
Crustal plates are spread apart = rifting
Molten material wells up b/wn separated plates, hardens, and forms ridges.
= new sea floor; aka sea-floor spreading.
Ex: Mid-Atlantic Ridge

8. Convergent Plate Boundaries
“Collision zones”; continental and oceanic crust collide.
Subduction = when the edge of the heavier plate sinks under the crust on the lighter plate
Deep ocean trenches
Mountain chain as the lighter plate is pushed up
Example: western edge of South America

9. Transform Plate Boundaries
Occur where plates slide laterally past one another at right angles to a sea-floor spreading center.
They neither diverge nor converge.
No volcanic eruptions.