The continents were once joined together in a single landmass and have since drifted apart.
continental drift
The continents were joined together in a supercontinent, or single landmass, about 300 million years ago.
Pangaea
Any trace of an ancient organism that has been preserved in rock.
Fossil
Form long chains of mountains that rise up from the ocean floor.
Mid Ocean Ridge
Adds more crust to the ocean floor. At the same time, older strips of rock move outward from either side of the ridge.
Sea Floor Spreading
Part of the ocean sinks back into the mantle, in a process that takes millions of years.
Deep Ocean Trench
Plates move apart of diverge from each other.
Divergent Boundary
Plates come together or converge.
Convergent Boundary
Plates slip past each other.
Transform Boundary
The theory that Earth's plates are in slow, constant motion, driven by convection currents in the mantle.
Plate Tectonics
Breaks in the Earth's surface where crust have slipped past each other.
Faults
A deep valley forms when pieces of Earth's crust diverge on land.
Rift Valley
A force that acts on rock to change its shape or volume.
Stress
Occurs when two plates pull apart.
Tension
Occurs when two plates come together.
Compression
Occurs where two plates slip past each other.
Shearing
The faulta cuts through rock at an angle, so one rock sits over the fault, while the other block lies under the fault.
Normal Fault
Has the same structure as a normal fault, but the blocks move in the reverse direction.
Reverse Fault
The rocks on either side of the fault slip past each other sideways, with little up or down motion.
Strike Slip Fault
A large area of flat land elevated high above sea level.
Plateau