• 1. What is a landslide and what causes one?
    A landslide is defined as "the movement of a mass of rock, debris, or earth down a slope" (Cruden, 1991). Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term "lands...

  • 2. Why study landslides?
    Landslides are a serious geologic hazard common to almost every State in the United States. It is estimated that in the United States they cause in excess of $1 billion in damages and from about 25 to 50 deaths each year. Globally, landslides cause billion...

  • Can major landslides and debris flows happen in all areas of the U.S.?
    Landslides can and do occur in every state and territory of the U.S.; however, the type, severity and frequency of landslide activity varies from place to place, depending on the terrain, geology, and climate. Major storms have caused major or widespread l...

  • Do human activities cause landslides?
    Yes, in some cases human activities can be a contributing factor in causing landslides. Many human-caused landslides can be avoided or mitigated. They are commonly a result of building roads and structures without adequate grading of slopes, of poorly plan...

  • How do landslides cause tsunamis?
    Tsunamis are large, potentially deadly and destructive sea waves, most of which are formed as a result of submarine earthquakes. They may also result from the eruption or collapse of island or coastal volcanoes and the formation of giant landslides on mari...

  • How many deaths result from landslides?
    An average of between 25 and 50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands. Most landslide fatalities are from rock fall, debris-flows, or volcanic debris flows (c...

  • How much do landslides cost in terms of monetary losses?
    In the United States, it was estimated in 1985 that the total dollar losses from landslides average between $1 billion and $2 billion per year. (As this is an old estimate, a more realistic number is between $2 billion and $4 billion per year, computed for...

  • How soon does the danger of landslides end after the rain stops?
    It’s not possible to exactly predict the number of days or weeks that landslides remain a danger after heavy rain. Residents near mountain slopes, canyons, and landslide prone areas should stay alert even after heavy rain subsides.   While...

  • Is there a landslide inventory for the United States?
    At this time there is no collective landslide inventory for the entire United States. For the status of state landslide inventories and links to other world landslide inventories please see: http://landslides.usgs.gov/regional/inventory/  ...

  • Is there a list of the largest landslides in the United States?
    Yes. The following link is a Web page with several versions of a list of the largest landslides in the United States: http://landslides.usgs.gov/learning/significantls.php Please Note: This list is currently being updated and is not complete. If ther...

  • Is there a list of the largest landslides in the World?
    The USGS has a Web page listing the largest landslides in the world at http://landslides.usgs.gov/learning/majorls.php The USGS also has this link to a list of the largest landslides in the United States: http://landslides.usgs.gov/learning/sign...

  • Is there more reference material available about landslides?
    Yes. The USGS Landslide Hazards Web site has an interactive bibliographic database (http://landslides.usgs.gov/learning/bibliography/) that can help you find landslide information. For more information contact Lynn Highland at: highland@usgs.gov Other USG...

  • Under what circumstances do U.S. Geological Survey landslide personnel conduct field work in landslide prone areas?
    USGS landslide researchers have ongoing field projects in several areas of the U.S., including parts of the Pacific coastal ranges, Rocky Mountains, and the Appalachians. USGS scientists also respond to major landslide events, including some that result in...

  • What areas are most vulnerable to landslides in southern California?
    Detailed locations of areas susceptible to debris flows are given on "Preliminary Soil-Slip Susceptibility Maps, Southwestern California," published as a U.S. Geological Survey Open-File Report (available on-line at): http://geopubs.wr.usgs.gov/open-file/o...

  • What can I do to be prepared for a landslide?
    Before a Landslide •Avoid building near steep slopes, close to mountain edges, near drainage ways, or natural erosion valleys. •Get a ground assessment of your property. •Contact local officials, state geological surveys or departments of...

  • What is a landslide hazard map?
    Several kinds of maps are used to depict danger from landslides. These maps may be as simple as a map that uses the locations of old landslides to indicate potential instability, or as complex as a quantitative map incorporating probabilities based on vari...

  • What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
    An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list...

  • What should I know about wildfires and debris flows?
      Wild land fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the af...

  • What was the biggest landslide in the world?
    The world's biggest historic landslide occurred during the 1980 eruption of Mount St. Helens, a volcano in the Cascade Mountain Range in the State of Washington, USA. The volume of material was 2.8 cubic kilometers (km).   The world's bi...

  • What was the most expensive landslide to fix in the United States?
    The Thistle, Utah, landslide cost in excess of $200 million dollars to fix (1984 dollars – adjusted for inflation this would be more than $400 million in 2010 dollars). The landslide occurred during the spring of 1983, when unseasonably warm weather ...

  • When does the U.S. Geological Survey issue a landslide advisory, and under what conditions?
    The U.S. Geological Survey derives its leadership role in landslide hazard-related work from the Disaster Relief Act of 1974 (the Stafford Act). The Director of the USGS has been delegated the responsibility to issue warnings for an earthquake, volcanic er...

  • Where can I find landslide information for my area?
    Every state in the US has a geoscience agency and most have some landslide information. The Association of American State Geologists provides links to the State Geologist for every state.  Also, your City and/or County may have a public works enginee...

  • Who can I talk to or contact for more information on landslides?
    The U.S. Geological Survey Landslide Information Center has a toll-free number at 1-800-654-4966, and can be reached by email at NLIC@usgs.gov. Most states have a state geological survey and many of them feature information about landslides. Visit the...