1. Earthquakes Vibrations of the earths crust Occur when rocks shift suddenly under a fault When friction prevents rocks from moving the fault is said to be locked Rocks come under stress Friction over come Rocks grind past each other Slippage causes trembling earthquakes

2. Elastic Rebound Theory Rocks on each side of the fault moving slowly If fault is locked stress on rocks increase Stressed past a certain point the rocks fracture Separate at weakest point Spring back to original shape or rebound As they fracture and slip they release energy in the form of vibrations called seismic waves Release of energy causes stress in other rocks causing them to fracture and spring back: aftershocks

3. Definitions Focus: area of a fault where slippage first occurs Epicenter: point on the earth’s surface directly above the focus

4. Focus can be Shallow Within 70 km of the earths surface Most damage caused here Intermediate Occur at a depth of between 70 and 300 km Deep Between 33 and 650 km By the time vibrations from intermediate focus or deep focus earthquake reach the surface, much of their energy has been used up. For this reason they do less damage

5. Fun fact *Earthquakes do not usually originate any deeper than 650 km because the high temperatures here cause rocks to act like plastics rather than fracturing.

6. Earthquake zones Pacific Ring of Fire Large earthquake zone Includes the west coasts of North and South America, the east coast of Asia and the western pacific islands of the Philippines, Indonesia, New Guinea, and New Zealand. Some plates are being subducted Some plates are being scraped past each other Plate movements cause stress to build up in the rocks They fracture and shift

7. Mid Ocean Ridge Oceanic crust pulling away from both sides of the ridge Causes stress in the rocks along the major ocean ridges

8. Eurasian- Mountain Belt – Eurasian plate colliding with African and Indian plates – Causes mountains and earthquakes – What mountain range is this causing (Himalayans)

9. Fault Zones Formed at plate boundaries because of intense stress when plates separate, collide, subduct or slide past each other Example San Andreas Fault: Pacific plate slipping along North American plate