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Disaster Hotspot Case Study California
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 below shows examples and locations of past
hazards that have caused disasters.
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
The Richter scale is a measure Francisco Bay area before 2025
of the energy released during 5. Past disasters include the San Francisco
an earthquake. earthquake of 1906 (magnitude 7.8) which along
with subsequent fires, destroyed much of the city
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.
1. A tsunami is a series of large waves that can flood coastal areas
2. They can be caused by earthquakes on the sea bed, or landslides into the sea
3. Earthquakes under the Pacific Ocean could cause a tsunami along the California coastline
4. An earthquake off the coast of Alaska in 1964 caused a tsunami to strike the coast of northern
California, killing 12 people in Crescent City
1. Landslides occur on unstable steep land. Land can be made unstable by coastal erosion or
extreme weather (rainstorms). Landslides can also be triggered by earthquakes
2. The risk of landslide disasters in California is high because of building on and around steep slopes,
as well as building on coastal land overlooking the ocean, E.g. La Conchita.
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1. There hasn't been a volcanic eruption in California since 1915 (Lassen Peak)
2. But there are volcanoes being monitored for potential eruptions, e.g. Lassen Peak, Mount Shasta,
and the volcanoes around Mammoth Lakes.
California is wealthy but Parts of the Population are Vulnerable
1. More than 70% of California's population live within 50km of a fault line