1. EVIDENCE FOR PLATE TECTONICS
Why Do Lithospheric Plates Move?

2. Heat Flow and Seafloor Elevations
Heat flow is a measure of the amount of heat leaving the rocks of the lithosphere.
The values of heat flow are unusually high in the areas around spreading centers and decrease away from the centers.
This is exactly what should happen if spreading centers are places where hot convection currents are bringing magma to the surface forming new oceanic crust.

4. Convergent Boundaries: Subduction
A subduction boundary is a form of converging boundary where one plate plunges beneath another overriding plate.
A characteristic feature of a subduction plate is a deep-sea trench. The deepest places on the ocean floor are in such trenches.

5. Earth Science Reference Tables

10. Why Do Lithospheric Plates Move?
Lithospheric plates rest upon the asthenosphere, which is a partially melted layer.
Convection currents within the asthenosphere are the driving force behind lithospheric plate movement. Within such currents, material expands and rises upon heating but contracts and sinks upon cooling.
Convection currents carry new material to the surface and pushes older material aside.

11. Why Do Lithospheric Plates Move?