2. Plate Boundaries
Plate boundaries are where plates interact with each other.
3 Type:
Divergent
Convergent
Transform

3. Tectonic Plates
The discovery of seafloor spreading led to the concept of continental plates.
The theory of plate tectonics states that Earth’s crust and rigid upper mantle are broken into enormous moving slabs called plates.

4. Divergent Boundary
Divergent boundary-plates move away from each other.
Geographical features: mid-ocean ridges (most common), rift valleys (boundary on land)
Animation

6. Convergent Boundaries
Convergent boundaries-plates move toward each other.
Oceanic-oceanic…..usually find island arcs, ocean trench
Oceanic-continental….usually find volcanic mountain range, ocean trench
Continental-continental…..usually find mountain range
Animation

10. Transform Boundaries
Transform boundary-plates slide past each other, fracturing the crust.
Animation

11. Mechanism for Plate Motion at Divergent Boundary
Ridge push -gravitational force that pushes plates away from one another.
Magma rises at mid-ocean ridges, heats the lithosphere around it, and rises.
Eventually cools, becomes more dense, sinks away from mid-ocean ridge.

12. Mechanism for Plate Movement at Convergent Boundaries
Slab pull -motion of cool, dense plate towards core due to subduction.
As plates move away from mid-ocean ridges, they become more dense. Subduction occurs when gravity pulls the more dense plate at a convergent boundary to sink and form an oceanic trench.
The weight of this sinking action causes a strong pulling force to continue to drag the rest of the plate.

13. Final Proposed Mechanism for Plate Movement
Mantle Convection-continued cycle of heated magma closest to the Earth’s core moving towards the lithosphere at mid-ocean ridges and returning to the direction of Earth’s core due to subduction at ocean trenches.
As magma, it warms up again, forming a circular current motion.