CONTINENTAL DRIFT Andrew Lisbon April 4/29/2014

Mr. Mendiola’s class

Pangaea The very large area of land that existed

as the only land on Earth about 300-225 million years ago, before it broke apart to form two large land masses, called Laragia and Gondwanaland.

Continental Drift The gradual movement of the continents

across the earth's surface through geological time.

Plates Tectonics A theory explaining the structure of the

earth's crust and many associated phenomena as resulting from the interaction of rigid lithospheric plates that move slowly over the underlying mantle.

plates A large section of Earth’s oceanic or

continental crust and rigid upper mantle that moves around on he asthenosphere.

Seafloor spreading Hess’s theory that new seafloor is formed

when magma is forced upward toward the surface at a mid-ocean ridge.

Lithosphere This rigid layer is about 100km thick and

general is less dense than material underneath the plastic like layer below the lithosphere called asthenosphere.

Asthenosphere The rigid plates of the lithosphere float

and move around on the asthenosphere.

Rift Valley When continental plates pull apart, they

can form rift valley. The African continent is separating now along the East African Rift Valley.

Subduction Where oceanic and continental plates

collide, the oceanic plate plunges beneath the less dense continental plate. As the plate descends, molten rock (yellow) forms and rise toward the surface, creating volcanoes.

Seafloor spreading A mid-ocean ridge, like the Mid-Atlantic

Ridge, forms where oceanic plates continue to separates. As rising magma (yellow) cools, it forms new oceanic crust.

Continental collision Where two continental plates collide,

they push up the crust to form mountain ranges such as the Himalaya.

Convection current A version of this same process, occurring,

in the mantle, is thought to be the force behind plate tectonics.