Also causes seafloor to rift apart at mid-ocean ridge. Continents move alont with ocean crust, and do not plow through it. Many seemingly unrelated geologic facts are unified by the plate tectonic theory. Brittle crust and uppermost mantle. Asthenosphere is partially molten part of mantle.
Plates move over hot spots creating a chain of volcanoes.
Hawaiian Islands, Emperor Sea Mounts Triple Junction - where three plate boundaries meet. Associated with divergent plate boundaries.