Earthquakes

S-Wave (Shear Waves)

Secondary waves that move side to side or up and down.

P-Wave (Primary Waves)

Pressure waves that move end to end.

Epicenter

The point on the Earth's surface directly above the center (focus) of an earthquake.

Earthquake

The shaking of the Earth's surface caused by tectonic plates shifting.

Lithosphere

A very strong layer of solid rock on the Earth through which both P-waves and S-waves can travel.

Shadow Zone

An area on the Earth's crust that does not receive direct P-waves or S-waves during an earthquake.

Outer Core

A layer of liquid rock that P-waves can travel through, but S-waves cannot.

Asthenosphere

A weak, slow-flowing, and easily deformed rock layer that P and S waves can pass through.

Convergent Boundary

A tectonic boundary where two plates collide into each other.

Transform Boundary

A tectonic boundary where plates rub or slide past each other.

Divergent Boundary

A tectonic boundary where plates move away from each other in opposite directions.

Geosphere

The solid part of the Earth, including the crust and interior, but excluding the oceans.

Mantle

The moving layer of rock located directly below the Earth's crust.

Oceanic Crust

The relatively thin, dense part of the Earth's crust that underlies the ocean basins.

Inner Core

The solid, very center of the Earth composed of iron and nickel.

Subduction

The process when one tectonic plate sinks under another plate due to differences in density.

Continental Crust

The thick part of the Earth's crust that forms the large landmasses.

Density

A measure of mass per unit volume, often expressed as \rho = m/V.

Convection

The movement based on temperature differences that drives the motion of tectonic plates.