Disaster Hotspot Case Study- California Flashcards
What is a disaster hotspot?
Vulnerable places at risk from two or more hazards.
Earthquakes in California
San Andreas fault runs length of California- conservative plate boundary.
Has two or three earthquakes each year- powerful enough to damage structures.
Good chance of an earthquake of magnitude 7.0+ hitting the San Fran Bay before 2025.
When do earthquakes occur?
When pressure between the plates builds up and then is suddenly released as they jerk past each other.
Causes of drought in California
Anticyclones (long lasting periods of high air pressure with sinking, dry air)- dry sinking air means no air.
La Nina events (periods when the surface water in the eastern Pacific Ocean is cooler)= less evaporation = less precipitation.
Increased wind blowing westward from the desert areas that are east of California, e.g from Arizona= the dry air has no moisture to cause precipitation.
What is the most devastating effect of drought in California?
Wildfires- dry vegetation is extremely flammable, so fires spread quickly over wide areas.
In Southern California, October 2007 killed 22 people and destroyed 1300 homes.
Tsunamis in California
A tsunami is a series of large waves that can food coastal areas.
They can be caused by earthquakes on the sea bed, or landslides into the sea.
Earthquakes under the Pacific Ocean could cause a tsunami along the California coastline.
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.
Landslides in California
Occur on unstable steep land. Land can be made unstable by coastal erosion or extreme rainstorm. Landslides can also be triggered by earthquakes.
The risk of landslide disasters in Cali is high because of building on and around steep slopes, as well as building on coastal land overloading the ocean, e.g La Conchita.
Volcanoes in California
There hasn’t been a volcanic eruption in California since 1915 (Lassen Peak).
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, why?
More than 70% of California’s population live within 50km of a fault line.
Lot of building on unstable ground.
Many buildings along coast (tsunamis).
Massive economy- huge losses.
What kind of plate boundary does California lie on?
Conservative.
Explain why California often experiences geophysical hazard events
Conservative boundary- pacific plate moving faster than north american plate.
Tsunamis.
Landslides/mudslides- caused by earthquakes.
Volcanoes in northern California where there is a destructive boundary region- subduction.
