Essential Questions What is an Earthquake? What is a Tsunami? What Causes Earthquakes? What are the Effects of Earthquakes? What is an Earthquake? An EARTHQUAKE occurs when part of the Earths crust suddenly shifts. In an earthquake, a sudden release of energy inside Earth sends waves moving upward and outward. These waves shake the ground. Earthquakes form cracks and faults along the surface. Earthquakes often cause other natural disasters Fires sometimes occur Tsunamis can start as a result of the powerful earthquake Earthquakes Earthquakes which occur on the ocean floor produce giant sea waves called tsunamis. Tsunamis can travel at speeds of 700 to 800 km per hour. As they approach the coast, they can reach heights of greater than 20 meters. Tsunamis Causes of Earthquakes Plates shift in earths outer crust. Stress occurs on rocks along faults. Excessive stress causes rocks to break. Rocks move into new positions. This causes the shaking of earthquakes. Where most Earthquakes occur San Andreas Fault The San Andreas fault extends 960 km from Mexico to the north of California. The land to the west is moving north. The land to the east of the fault is moving south. All the rocks do not move at the same time so earthquakes occur in one area and then another. How Earthquakes Move Looking at this picture, A represents the EPICENTER- the place in which the earthquake started. Waves travel outward from the epicenter. B represents the first city that will experience the effects of the Earthquake. Interesting Fact Earthquakes rarely kill people Building collapses do! Interesting Fact Even buildings left standing are dangerous. There is often structural damage. Effects of Earthquakes People are often left homeless. They must find temporary housing. Effects of Earthquakes Looting (stealing) often takes place. Chaos usually makes things worse. Police patrols are necessary. Devastating Examples from History San Franciscos famous earthquake of 1906 Quake caused damage to some buildings. Other buildings were undamaged. Look at some scenes from 1906. San Francisco, California Earthquake Of 1906 Lets Review What other major natural disaster do earthquake sometimes cause? a) Volcanoes b) Tsunamis c) Hurricanes d) Tornadoes Lets Review What causes strong earthquakes to happen? A.) A strong earthquake is caused by a sudden slip on a fault B.) A strong earthquake is caused by people, as in explosions Lets Review The region of the United States with the most earthquakes is...? A.) the North B.) the South C.) the West D.) the East Lets Review Earthquakes usually happen along cracks in the earth's crust called...? A.) Jagged lines B.) Fault Lines C.) Layers D.) Wrinkles Lets Review EXTENDED RESPONSE As weve learned- earthquakes are a fast-moving change to Earths surface. Discuss at least five things about the destructiveness of earthquakes. Include any or all of these: Causes Effects on people or land Examples