Sea Floor SpreadingA parallel pattern of rock material found

at identicallocations on each side of the Mid-Atlantic

Ridge revealsrock of the same geologic age.

Divergent BoundaryThe boundary between two tectonic plates moving awayfrom each other—on land creates rift valleys, on the seafloor creates new ocean crust and mountainous ridges.

Convergent BoundaryThe boundary between two tectonic plates moving

toward each other resulting in volcanic activity when adenser ocean plate subducts, or moves below a

continental plate or another oceanic plate.

Transform BoundaryThe boundary between two plates that slide past one

another—sudden shifts that result in major geologicalevents such as earthquakes and the release of stored

energy

Connection currentsA cyclical motion occurs because of density differencesin the mantle. Heated, less dense lower regions of the

fluid mantle rise, and denser, cooler regions sink due togravity. The combined motions serve as the engine for

crustal plate movement.

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