Advertisement Upgrade to remove ads

seismic waves

Vibrations that travel through Earth carrying the energy released during an earthquake.


The force exerted on a surface divided by the total area over which the force is exerted.


The layer of rock that forms Earth's outer surface.


A dark, dense, igneous rock with a fine texture, found in oceanic crust.


A usually light-colored igneous rock that is found in continental crust.






The soft layer of the mantle on which the lithoshpere floats.

outer core

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

inner core

A dense sphere of solid iron and nickel at the center of Earth.


The direct transfer of energy through space by electromagnetic waves.


The direct transfer of thermal energy from one substance that it is touching.


The transfer of thermal energy by the movement of fluid.


The amount of mass of a substance in given volume; mass per unit volume.

convection current


continental drift

The hypothesis that the continents slowly move across Earth's surface.





mid-ocean ridge

An undersea mountain chain where new ocean foo is produced.



sea-floor spreading


deep-ocean trench



The process by which oceanic cus sinks beneath a deep-ocean trench and back into the mantle at a converent plate boundary.


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

scientific theory


plate tectonics

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


A break or crack in Earth's lithosphere along which the rocks move.

divergent boundary

A plate boundary where two plates move away from each other.

rift valley

A deep valley that forms where two plates move apart.

convergent boundary

A plate boundary where two plates move toward each other.

transform boundary

A plate boundary where two plates move past each other in opposite directions.

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!



Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom


Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording