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outer core

a layer of molten iron and nickel that surrounds the inner core of Earth

lithosphere

the rigid outer layer of earth, including the crust and upper mantle

plate boundaries

a crack in the lithosphere where two of Earth's plates meet

inner core

a dense sphere of solid iron and nickel at the center of Earth

crust

the layer of rock that forms Earth's outer surface

geology

the study of the solid Earth

mantle

the layer of hot, solid material between Earth's crust and core

plates

a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust

plate tectonics

The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle.

Pangea

Large ancient land mass that was composed of all the continents joined together.

divergent plate boundary

boundary between tectonic plates in which the two plates move away from each other, and new crust is created between them (tension)

convergent plate boundary

boundary between two colliding plates, often associated with mountain building ocean trenches and volcanic islands (compression)

transform plate boundary

Boundary between two plates that are sliding past each other. (shearing)

magma

the molten mixture of rock-forming substances, gases, and water that makes up part of Earth's mantle

asthenosphere

upper part of the mantle on which the plates move

tension

stress that stretches rock so that it becomes thinner in the middle

shearing

stress that pushes a mass of rock in opposite directions

compression

Stress that squeezes rock until it folds or breaks.

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