It would be hard to find a place in the world that did not have any natural hazards.  But California seems to have an extra share.  If you look at a map of natural hazards of the 48 contiguous states, put together by the U.S. Geological Survey,  California ranks high in four of the six major natural hazards mapped. And there are other hazards that do not appear on the map.  Why does California have so many natural hazards?  The answers lie in the geography of the state: its geology and climate, and also in the way humans have used and misused the landscape and resources.

Natural Hazards Information     Earthquakes    Volcanos    Tsunamis     Floods     Wildfires    Landslides     
Books about Natural Hazards

Natural Hazards Information

• To get a better understanding of much of the geological background of many natural hazards, read This Dynamic Earth: the Story of Plate Tectonics, an online textbook from the USGS.

• Savage Earth, from PBS Online, is an informative, dramatic site that covers earthquakes, volcanoes, and tsunamis, as well as plate tectonics.  It has a lot of very good animations of subduction zones, erupting volcanoes, faulting and seismic waves, and tsunamis.

• Make your own Hazards Map  Put in your zip code or other location information, then choose your hazard--floods, earthquakes, hurricanes, windstorms...and get a printable map of hazards in the area of your choice.  From FEMA and ESRI.

• FEMA, the Federal Emergency Management Agency, is the agency responsible for planning for and dealing with disasters.

• California Office of Emergency Services is the state agency that deals with disasters.   There is information here on preparing for a disaster, on current situations, and links to other information on hazards.

• Natural Disasters: Forecasting Economic and Life Losses is a report from the USGS discussing forecasting of natural disasters, and estimating potential losses.

• USGS Natural Hazards Programs: Lessons Learned for Reducing Risk is a brief report which discusses a variety of disasters. 

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Earthquakes  When people think of California, one of the first words that usually comes to mind is "earthquake."  California has earthquakes because it is located in a tectonically active area, where three tectonic plates come together.  The western section of California, west of a line running from the Imperial Valley in the south to the San Francisco area in the north, is on the Pacific Plate, which is moving towards the northwest at an average rate of about 5.5 centimeters per year.  East of that boundary is the North American Plate, which is moving more slowly towards the west.   (See this Plate Boundary Map).   As the huge plates grind past each other, stress builds up over the years, until eventually the rock ruptures and there is movement.  The shockwaves from this movement are felt as earthquakes.  Faults are the fractures along which movement takes place.  The most famous is the San Andreas Fault, which runs from the Salton Sea area to San Francisco, goes offshore just south of the city of San Francisco, then comes ashore again briefly a couple of times before leaving land for good near Cape Mendocino. But the San Andreas is not the only fault along which an earthquake can occur. It is just the largest fault of a large complex of more or less parallel faults making up the San Andreas Fault Zone.  Other well-known faults that are part of this complex include the Elsinore and San Jacinto Faults in Southern California, and the Hayward and Calaveras faults in the north.  At different times one or another of the faults in this zone may rupture and move.
    Movement along the faults is not predictable at this point, although we can look at patterns of past movements and come up with the probability that a particular segment of a fault may move within a given time span. (See Quake Forecasting--An Emerging Capability). One problem arises when a fault is not perfectly straight, but has a bend.  Take a look at the so-called Big Bend in the San Andreas Fault, north of Los Angeles.  This bend makes it difficult for the plates to slide past each other easily.  So stress may build up for many years, before a big earthquake occurs.   There are several places in the San Andreas Fault Zone where bends in faults may lock the fault and allow stress to build up.
    Another tectonic plate associated with California is the Gorda Plate (with the Juan de Fuca Plate to the north of it).  These are relatively small plates that are subducting under the northernmost part of California, as well as Oregon, Washington, and British Columbia.  They form the Cascadia subduction zone, which is responsible for the volcanos of the Cascade Range.  The largest earthquakes occur in subduction zones, as one plate pushes under another.  Within historic times, no large subduction zone earthquakes have occurred in the Pacific Northwest, but there is increasing evidence that huge quakes have occurred there in the past.
    If you want to know more, try the books referenced below, or see Plate Tectonics history of California, from the USGS.  More geology information may be found on the Natural History page as well.  Also, see Tsunami information below.
    There is an overwhelming amount of information on the Internet about earthquakes.  A few pertinent sites are referenced below, but most of these have links that will keep you busy learning about faults and earthquakes for years to come.

• Recent Earthquakes in California is a map that is updated every hour, or within 5 minutes of` an earthquake.
• A Decade of Notable California Earthquakes summarizes information on several famous recent earthquakes, includes maps of faults and earthquake locations, and discusses probabilities of future earthquakes.
• California Has Its Faults is a good introduction to what a fault is, and the different types of faults, along with a map of some major faults in California.  You've got to like the title for this page.  From the California Division of Mines and Geology.
• Virtual Earthquake will help you learn how to read a seismogram, locate the epicenter, and determine the Richter Magnitude of  a quake.  From Cal State L.A.
• Make Your Own Seismogram.  Choose the station, time, and other parameters. Or, see some selected seismograms of interesting earthquakes.
• Live seismograph: Memento mori "displays streaming seismographic data measured continuously from a site near the Hayward Fault above University of California at Berkeley,"  from Berkeley Seismological Laboratory. This is a philosophical and artistic approach: "a web interface to the earth."
• San Andreas Fault aerial photos, mostly from the 1930' and '40's..
• The USGS on Earthquake Hazards and Preparedness is a tremendous source of information.
• Putting Down Roots in Earthquake Country is an excellent online handbook on earthquakes, put out by the Southern California Earthquake Data Center.  It explains some of the geology of earthquakes, and has a lot of information on making homes and buildings safe in a quake, as well as advice on personal safety.
• Living on Shaky Ground: How to Survive Earthquakes and Tsunamis on the North
  Coast, from the Humboldt State Earthquake Education Center, has background information on earthquakes and tsunamis, as well as advice on preparedness and survival.
• Seismic Hazard Zone Maps, mostly for Southern California, from the Division of Mines and Geology.
• Northern California Earthquake Data Center is the main center for data on earthquakes in Northern California.  There is a tremendous amount of information that can be found from this page.
• The Great 1906 San Francisco Earthquake tells the whole story, with photographs.
• When Will the Next Great Quake Strike Northern California? from the USGS.
• Bay Area Shaking Hazard Maps can be accessed from this page. 
• ABAG Earthquake Maps and Other Information: just about everything you ever wanted to know about earthquakes in the Bay Area (and elsewhere).
• Southern California Earthquake Data Center collects seismological data for Southern California, and is a major source of information.  
• Seismic Hazards Map, Probable Earthquakes, 1994-2024, for Southern California, might be interesting for anyone living in Southern California.
• Southern California Earthquakes is a clickable map showing historic earthquakes going back as far as 1812, with magnitude and other information.
• Earthquake Information from the USGS's Pasadena office is an excellent site with a lot of interesting quake information and links.  This is a good place to start.
• The Seismological Laboratory  at CalTech is another good place to learn about earthquakes.
• Just in case you think you're missing something, Seismolinks has links to just about everything else about earthquakes.

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Volcanos  People think about volcanos in connection with Alaska and Hawaii, but California has several active and potentially active volcanos, that could pose a hazard.  In the northern part of the state are several volcanos belonging to the Cascade Range.  The most notable of these in California are Lassen Peak and Mt. Shasta.   Lassen Peak last erupted between 1914 and 1917.  Shasta has not erupted in historic times, but has probably erupted at least three times in the last 750 years, and may have erupted as recently as 1786.  Mt Shasta in particular is potentially dangerous, because there is ample evidence that past eruptions have sent pyroclastice flows (flows of hot volcanic gases, ashes, cinders, and other debris) down the slopes.   There have also been some very large volcanic mudflows that have surged down the slopes of Shasta.  In fact, several towns are built on the site of old flows, and could be in the way of danger if the volcano should erupt again.
    In addition to the Cascade Volcanos, Long Valley, in the Mammoth area of the Eastern Sierra, seems to be over a hot spot or mantle plume, where magma from the mantle wells up into the crust.  Long Valley itself is a giant   caldera (a large volcanic depression, sort of a mega-crater), that formed in a huge explosive eruption about 700,000 years ago.  The explosion formed a caldera which is about 15 kilometers wide by 30 kilometers long, and covered the surrounding 1500 square kilometers with pyroclastic flows up to hundreds of meters deep.  Ashes from the eruption have been found as far east as Kansas. While no one expects a similar explosion anytime in the foreseeable future, small eruptions are a possibility.  Eruptions in the area occurred about 400 to 500 years ago around Inyo Craters, and 250 years ago at Mono Lake, 20 kilometers to the north. (In case 700,000 years seems like a long time to you, consider that the lifespan of a volcano may be measured in the millions of years, so 700,000 years is not a terribly long time to a volcano).  Starting in 1980, swarms of earthquakes in the area suggested that magma was again moving up from below, and the USGS has established a volcano observatory to monitor conditions.

• To learn about volcanos in general, Volcanos, by Robert I. Tilling, is an online version of a book from the USGS.  It covers topics ranging from the types of volcanos and eruptions to plate tectonics to people and volcanos.
• Volcanos of the United States, from the USGS, is an online publication that will give you an introduction to volcanos in several areas of the US.                            Figure from online edition of This Dynamic Earth)
• Images of California Volcanoes, from the Cascades Volcano Observatory of the USGS. Images of Mt. Shasta (see the photo above right), Lassen, the Long Valley area, and the Medicine Lake area.
• California Volcanos and Volcanic Areas  EVERYTHING about California volcanos is here.  Individual volcanos and volcanic regions are covered, with background information, maps, photos, discussion of hazards.  This site is a must!  From the USGS.
• A summary table of Active and Potentially Active Volcanos in California.
• What to do if a Volcano Erupts, from the American Red Cross.  You might need this information some day!
• Long Valley Observatory is the USGS monitoring station for Long Valley Caldera, and is the place to go to find out about vulcanism in this area.
• Future Eruptions in California's Long Valley Area--What's Likely? is a publication by the USGS.
• Living With a Restless Caldera--Long Valley, California.  Also a publication from the USGS.
• Cascades Volcano Observatory  studies and monitors volcanos in the Cascade Range, from Lassen Peak and Mt. Shasta northward to the volcanos of the Pacific Northwest.  They have a very good website, with links to just about everything else about volcanos.
• Living with Volcanic Risks in the Cascades is a fact sheet covering each Cascade volcano.
• The May 1915 Eruptions of Lassen Peak, California is an article published in Volcanic Hazards, Assessment and Monitoring, in 1989.
• Living with Volcanos, from the Cascades Volcano Observatory, includes a tremendous amunt of background information on volcanos, as well as sections on historic eruptions, volcanos in movies and books (check the Dante's Peak FAQ), and how to become a volcanologist.
• Volcano and Earth-Science Oriented Websites is a big list of sites from the CascadesVolcano Observatory, covering volcanos around the world.

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Tsunamis   Tsunamis are seismic sea waves, caused by movements along faults, undersea landslides, volcanic eruptions, and similar catastrophes.  They are occasionally referred to as tidal waves, but this is incorrect, since tides are not the cause of tsunamis.  Since California is a seismically active region, prone to earthquakes, as well as to volcanic activity, tsunamis along the coast are a possiblity.  There is particular concern along the north coast, in the Cascadia subduction zone, since a subduction-related earthquake could generate a large tsunami.  Since the source of the waves would be close to the coast, such a tsunami would come onshore with little warning, and could be devastating.  One tsunami has caused deaths in Northern California in historic times: the Alaska earthquake of  1964 generated a tsunami that killed 12 people in Crescent City, California (and 122 people in Alaska).  Authorities concerned with natural disasters are taking the possibility of tsunamis in California seriously.

• What is a Tsunami? is a fact sheet from the Federal Emergency Management Agency.
• The West Coast and Alaska Tsunami Warning Center continuously monitors for earthquakes and evaluates the potential of each earthquake for generating a tsunami.  Advisories, watches or warnings are issued as needed.   This site has a wealth of information on tsunamis, from their physics to some pictures of tsunamis.
• Photos of tsunamis from NOAA (not in California).
• The Physics of Tsunamis discusses how tsunamis are generated.
• Tsunami Hazard Mitigation is a very sobering report by NOAA to the Senate Appropriations Committee. It discusses the risk of tsunamis to the Pacific Northwest (including the Northern California coast, the need for education and early warning systems, and makes recommendations for mitigation of hazards.  The map of areas in Eureka, California, that could potentially be inundated by a tsunami should certainly give some food for thought.
• Tsunami! Information and links from Humboldt State University.
• Redwood Coast Tsunami Work Group is a group of federal, state and local organizations in  Humboldt, Mendocino and Del Norte Counties, working on finding ways to mitigate hazards from tsunamis in the region.
• Local Tsunamis and Earthquakes along the Cascadia Subduction Zone, from the USGS, is a good discussion of the tsunami risk in the Pacific Northwest.
• Cascadia Earthquakes and Tsunami Hazard Studies is another USGS report which covers the hazards in the subduction zone.
• Tsunamis is part of a brochure put out by Humboldt State's Earthquake Education Center.  It includes background information on tsunamis, some interesting photographs of tsunami damage in Crescent City, California, and advice on survival if a tsunami strikes.
• A little bit on The Southern California Tsunami Hazard.  Not much information here yet, but it should be interesting as more is learned.
• Tsunami! from the University of Washington, is a good website on tsunamis in general.

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Floods 

• Homeowner's Guide to Retrofitting: Six Ways to Protect Your House from Flooding is a book available on line (in Adobe PDF format) from the Federal Emergency Management Agency.  If you live in a flood zone, this might be a very good book to have!
• Flood Status Overview has clickable maps of Northern and Southern California with current information on the flood status of rivers.
• Here is the National Weather Service (San Francisco Bay Area) Rainfall & River Page, with a tremendous amount of information on precipitation and river status for most of Central and Northern California.
• River Stage Information is a single page of general information on floods, with diagrams showing leveed and non-leveed rivers, and the various stages of the river from normal low flow to flood stage.
• River Stage and Flow Information will give you current information on the river livels and status of rivers in California, as well as access to a lot of other pertinent information on river flows. From the California Department of Water Resources, Division of Flood Management.
• Here is the National Weather Service's page for California Flood Warnings.
• Bay Area Flooding Hazards 
• Dam Inundation Maps   "represent the best estimate of where water would flow if a dam failed completely and suddenly with a full reservoir".  Cheerful thought. Mapped by county.  From the Governor's Office of Emergency Services.
• Speaking of dam disasters, the worst dam disaster to occur in California was the failure of the St. Francis Dam, north of Los Angeles, in 1928.  Designed by William Mulholland, the dam began to leak as soon as it was filled, and on March 12, 1928, the dam failed completely, sending a wall of water up to 200 feet high surging down the canyon.   Of 75 families living in San Francisquito Canyon, below the dam, only one person survived.  The number of dead is not accurately known, but it may have been as high as 450.  Read a summary of the St Francis Dam Disaster, or see before and after photos and links at this San Francisquito Dam page. If you want a really dramatic, more detailed account of the disaster, read chapter 2 of Marc Reisner's Cadillac Desert (referenced in the books section of Water Resources).
• Dam Failure Inundation is a brief discussion on causes of dam failure.
• For more on dams in general, see the page on Water Resources.
• Northern California Storms and Floods of January 1995 is a report by the USGS on the unusual storms and floods that damaged Northern California.

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Wildfires. Wildfires are common in California.  They are a natural part of the environment here.  The climate in much of California is a mediterranean type of climate, which is characterized by mild rainy winters and warm (or hot) dry summers.  Vegetation grows during the winter and spring, and dries out during the long dry summers.  The greater the growth of vegetation in the wet season, the more fuel there is to burn. In the parts of California covered by chaparral vegetation, fire is always a danger, because chaparral plants are often very flammable.  This plant community is in equilibrium with a regime of relatively frequent fires, and fire can actually be beneficial to many of the plant species.  Fire releases nutrients from dead plant material back to the soil, allowing new growth the following season. Many chaparral species contain volatile oils that allow them to burn very well, and many of these species are adapted to resprout after a fire, or seed in to a burned area.
Even parts of California that are not in the mediterranean climate zone can have big fires, because a long drought period can dry out the vegetation sufficiently for it to burn.  Fires have always occurred naturally, set by lightning.  The lightning-set fires in the past may have been more frequent (because they were not suppressed) but probably covered smaller areas, and were not as hot and devastating as some fires now, because the high frequency meant that there was less chance for a big load of fuel to build up. If we suppress fires for many years, there will be a buildup of fuel as plants grow larger, and dead wood and other plant material accumulate.  Eventually, perhaps at the end of a hot, dry summer, something will set off a fire, and if the weather conditions are right (or wrong), it can potentially be a very big fire because of the accumulated fuel load. 
Fire weather in California is hot and dry and windy.   The right conditions for dangerous fires occur when hot dry winds blow towards the coast from inland areas.  The winds are the result of high pressure systems over the Great Basin region, pushing the air outwards. As the warm air flows down from higher elevations, it warms up and dries out still more.  Such strong, dry winds can rapidly dessicate the vegetation, and can  provide the perfect weather conditions for a devastating fire.
Following a fire, the burned areas often experience flooding, excessive soil erosion, and landslides, because the bare slopes cannot hold the soil as well as a vegetated slope would.

• Current Wildland Fire Information will give you information on fires taking place right now (in California and elsewhere in the West).  There is information on current status and estimated containment, with maps, incident reports, fire weather information, and a summary on the current fire season. From the National Interagency Fire Center in Boise Idaho; their home page has a great many fire-related links.
• Living more Safely in the Chaparral-Urban Interface by Klaus W.H. Radtke, is a general technical publication by the Pacific Southwest Research Station of the USFS.  The entire text is available in Adobe PDF format.  This is a 50 page report, and a long download, but worth it. It is an authoritative report on the problems of living in the natural chaparral vegetation of California.  Topics covered include the ecology of the chaparral, fire in the chaparral, watershed management, landscaping for fire and erosion control, and other home and personal safety topics.  This is a useful introduction to understanding the fire regime in chaparral and the flooding and erosion that may follow a fire, as well as some ideas on how to live in this environment.
• Protecting Residences From Wildfires, by Howard Moore, is another general technical publication from the USFS.  This one is available in html.  It is very practical and comprehensive, and could save your house.
• Homeowners Checklist, How to make your home firesafe,  California Department of Forestry 
• Lista de Control para Propietarios, Como proteger su casa contra los incendios, CDF.
• The Fire Effects Information System (FEIS), from the USFS, is a database of information on the fire ecology of a vast number of species of plants and animals, from trees to ferns, to mammals to birds.  There is a great deal of general ecological information on each species, as well as a discussion of the species' response to fire. For example, this page on the moose has information on distribution, life history and habitat requirements, effects of fire on the species, and a list of references.   This is a very useful database if you are interested in this topic.
• The USFS Riverside Fire Laboratory  does research on wildfires.  This page will give you access to information on their projects.
• Some good links to information on fires, from the National Park Service.
• The home page of the California Department of Forestry and Fire Protection.
• The California Fire Plan, A Framework for Minimizing Costs and Losses from Wildland Fires,  from the CDF.
• CDF 2003 Fire Season Statistics.
• Many Historical Statistics on fires, from CDF
• USGS Wildland Fire Research  is a report on research being done by the USGS on wildfires.
• National Fire Weather page from the National Weather Service.
• Use GEOMAC for mapping wildfires.

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Landslides 

• The California Department of Conservation has a program to identify and map hazards from earthquakes and landslides, as well as other geologic hazards.
• San Francisco Bay Region Landslide Folio, from the USGS, has maps of landslide area in the Bay area, as well as a great deal of other information.
• Some photos of 1998 El Niņo Storm Damage to California State Highways from Caltrans.  Like the photo shown of Route 96 in Siskiyou county, these are mostly landslides.
• The USGS also has some animations and movies of landslides in Northern California.  These  include computer simulations of landslides and fly-bys of landslides.  The files are very large.

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Books on Natural Hazards  For some reason, there are a lot of books on natural hazards written by geologists in California.  Even books written by people outside of California have a lot of examples of hazards in California.  Here are a few good books to try, but these are just a sampling; there are many more on these subjects.

Abbott, Patrick L. 1996. Natural Disasters.  Dubuque, IA: Wm. C. Brown Publishers.  This is a very interesting, readable book written by a geology professor at San Diego State.  Clear explanations on how things work, covering such topics as plate tectonics, earthquakes, volcanos, landslides, fires, space objects...you get the idea.  There are a lot of lively, fascinating descriptions of past disasters, and many examples of hazards in California.  This book is an excellent place to start, if you are interested in natural hazards.

Decker, Robert, and B. Decker.  1998. Volcanoes.  New York: W.H.Freeman and Co.  A good general introduction to volcanos.

Keller, Edward A. 1996. Environmental Geology. New Jersey: Prentice-Hall.  A textbook covering natural hazards and human impact on the environment.  Written by a geology professor at UC Santa Barbara, there are many examples taken from California.

Levy, Matthys, and M. Salvadori. 1995.  Why the Earth Quakes, The Story of Earthquakes and Volcanos. New York: W.W. Norton and Company. A readable, general introduction to this topic.  I especially like the parts that discuss efforts to make structures resistant to earthquakes.

Murck, Barbara W., B.J. Skinner, and S.C. Porter.  Environmental Geology.  New York: John Wiley and Sons, Inc.   A very good, readable textbook, that covers hazards from volcanos to floods to landslides (and a lot more), and human impacts on environment, including such topics as resource depletion, toxic and solid wastes, and air and water pollution.

Robinson, Andrew.1993.  Earth Shock-- Hurricanes, Volcanoes, Earthquakes, Tornadoes and Other Forces of Nature.  London: Thames and Hudson.   Just what the title says.  Lots of good photos.

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  Comments, Questions, or Suggestions? Email: J.R. Thorngren
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06/07/06

The grizzly bear is the state animal of  California, and is the bear on the California flag.  There are no grizzly bears in the wild in California today.   The last one in the state was killed in 1922, or possibly in 1924.