PLATE TECTONICS - a theory explaining the structure of earths crust
CONTINENTAL DRIFT - the movement of the continents across the earths surface through geological time
PANGEA - when all the continents were once one continent 300 million years ago
ASTHENOSPHERE - the upper layer of earths mantle
LITHOSPHERE - the outer part of the earth
MID-OCEAN-RIDGE - a long, seismically active submarine ridge system situated in the middle of an ocean basin and marking the site of the upwelling of magma associated with seafloor spreading
RIFT VALLEYS - a large elongated depression with steep walls formed by the downward displacement of a block of the earth's surface
SUBDUCTION - the sideways and downward movement of the edge of a plate of the earth's crust into the mantle beneath another plate.