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continental drift

The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations

Pangaea

A large "supercontinent" that is believed to have connected all of the continents on earth about 225 million years ago.

seafloor spreading

The process that creates new sea floor as plates move away from each other at the mid-ocean ridges

plate tectonics

A theory stating that the earth's surface is broken into plates that move.

plates

Large section of Earth's oceanic or continental crust and rigid upper mantle that moves around on the asthenoshpere

lithosphere

rigid layer of earth made up of the crust and the upper part of the mantle

asthenosphere

The solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it

convection current

Cycle of heating, rising, cooling, sinking that makes plates move.

mantle

largest layer of rock between Earth's crust and core containing the lithosphere and asthen0sphere

converge

A boundary where plates are coming towards each other

diverge

A boundary where the plates are moving away from each other.

transform

A boundary where the plates are sliding past each other

plastic-like

not completely solid or liquid; capable of being molded or changing form

oceanic crust

earth's crust located under the ocean

continental crust

The portion of the earth's crust that is less dense than oceanic crust

subduction

The process by which an oceanic tectonic plate sinks under another plate into Earth's mantle; when one plate sinks beneath another

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