Plate Tectonics- a theory about how earthquakes, tsunamis and volcanic eruptions happen
Continental Drift- the theory about how the continents drifted apart
Pangaea- the theory that the continents were once together as one
Asthenosphere- the upper layer of the Earths mantel
Lithosphere- the outer part of the earth
Mid-Oceanic ridge- underwater mountain systems
Rift valleys- steep walls formed between two parallel faults or parallel system
Subduction- sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.