California: Disaster Hotspot

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California is a disaster hotspot. Disaster hotspots are vulnerable places at risk from two or more hazards. The state of California in the USA has many highly populated towns and cities at risk from a variety of hazards. The map shows examples and locations of past hazards that have caused disasters. Earthquakes 1. The San Andreas Fault runs the length of California – it’s a conservative plate boundary. 2. Earthquakes occur when pressure between the plates builds up and then is suddenly released as they jerk passed each other. 3. California has 2 or 3 earthquakes each year that are powerful enough to damage structures (5.5+ on the Richter scale) 4. Studies of their frequency and magnitude of past earthquakes show that there’s a good chance of an earthquake of magnitude 7.0+ hitting the San Francisco Bay area before 2025. 5. Past disasters include the San Francisco earthquake of 1906 (magnitude 7.8) which along with subsequent fires destroyed much of the city. Droughts 1. Droughts in California can be caused by anticyclones (long-lasting periods of high air pressure with sinking, dry air. Dry, sinking air means no rain. 2. Drought can also be caused by La Nina events (periods when the surface water in the eastern Pacific Ocean is cooler). This means less evaporation, so there’s less precipitation. 3. Another cause of drought is increased wind blowing westward from the desert areas that are east of California, e.g. Arizona. The dry air has no moisture to cause precipitation. 4. The most devastating effect of drought in California is wildfires – dry vegetation is extremely flammable, so fires spread quickly over wide areas. 5. The wildfires in Southern California in October 2007 killed 22 people and destroyed 1300 homes. Tsunamis 1. A tsunami is a series of large waves that can flood coastal areas. 2. They can be caused by earthquakes
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