 Earthquake: the shaking of the Earth’s crust caused by a release of energy.  Common cause: movement of the Earth’s plates

 As the Earth’s plates move past one another, friction causes the plates to get “stuck”. · Stress and pressure builds up and causes the plate to become deformed (bend) as it continues to try and move (the plates are elastic-they can change shape). · Eventually, the pressure is great enough to overcome the friction and the plates slip past one another. · The plate movement is the earthquake. The greater the plate movement, the larger the earthquake. · The plates are in a new location, but they go back to their original shape (rebound). **Think of pushing on the ends of a wooden ruler. As you push, the ruler will bend. When you release the pressure on the ends, the ruler snaps back to its original shape.

 Fault: break in the lithosphere along which movement has occurred  Focus: the point at which the first movement occurs  Epicenter: the point on Earth’s surface directly above the focus

 Friction prevents plate movement most of the time.  Boundary Type vs. Earthquake Depth: a. divergent boundaries: within 30 kilometers of the surface b. transform boundaries: occur at shallow depths c. subduction boundaries: occur as deep as 700 km

 Body wave: travels from the focus of an earthquake through Earth  P-wave: a body wave that squeezes and stretches rock materials - also known as a compression wave or a primary wave - P-waves can travel through any material- solid, liquid or gas

 S-wave: a body wave that causes particles of rock to move at right angles -also known as shear waves or as secondary waves -can travel through only solids, not liquid or gas

 P and S waves P and S waves

 Surface wave: a wave that travels along Earth’s surface- caused by body waves  Surface waves cause considerable damage

 The rate at which P waves and S waves travel depends on the type and density of the material through which they travel  The waves move faster when material is rigid and dense  S waves travel at a little less than half the speed of P waves  Surface waves travel the slowest when compared to P and S waves