California landslides

Landslides in California occur mainly due to intense rainfall but occasionally are triggered by earthquakes. Landslides are common in Southern California, the San Francisco Bay Area and other parts of Northern California, and the Sierra Nevada. Although they most often are reported when they impact residential developments, landslides also damage roads, railroads, pipelines, electrical lines, and other infrastructure throughout the state, and occur in unoccupied parts of the state.

California Geological Survey

CGS is California's primary source of geologic and seismologic products and services for decision making by California's government agencies, its businesses and the public.[1] Since the 1960s, when it was known as the California Division of Mines and Geology, CGS has produced many maps that depict landslide features and potential slope-failure areas. CGS products have included geologic maps and reports for land-use planning, landslide hazard identification maps, watershed maps, and earthquake-triggered landslide-zone maps. Many of these maps were advisory in nature: cities and counties could choose to use or ignore them.[2] However, watershed maps are routinely used in the review of timber harvest plans outside federally owned lands.[3] CGS has a legislatively mandated Seismic Hazards Zonation Program that produces regulatory maps areas where the probability of liquefaction and earthquake-triggered landslides are significant enough to require site evaluation prior to most developments.[2]

Landslide maps in California and laws and regulations

The State of California Department of Conservation produces regulatory maps showing locations where the hazard from earthquake-triggered landslides must be evaluated prior to specific types of land-use development in accordance with provisions of Public Resources Code, Section 2690 et seq. (Seismic Hazards Mapping Act). These maps and related products incorporate evaluations of probabilistic ground shaking and existing geologic conditions. Recently released landslide inventory and related hazard zone maps are available free from the CGS website.[4] Watershed maps, used in the review of timber harvest plans (regulated by the California Department of Forestry) are available for downloading in PDF and GIS data formats.[5]

From 1983 through 1994, CGS was directed to produce Landslide Hazard Identification Maps under the State's Landslide Hazard Identification Act. Though of high quality and designed for land-use planning purposes, the Act did not require local governments to use the maps. The Act was repealed January 1, 1995 per a sunset provision in the Act.[2] Those maps, and many older non-regulatory landslide-related products are available for purchase from CGS offices and/or available for download from the CGS website.

List of historic California landslides

See also


  1. ^ "Welcome to the California Geological Survey". California Geological Survey. Retrieved 3 March 2012.
  2. ^ a b c Smith, Theodore C.; McKamey, Bea (2000). "Summary of outreach activities for California's Seismic Hazards Mapping Program, 1996–1998". California Division of Mines and Geology Special Publication 121.
  3. ^ "Forest and Watershed Geology Program". California Geological Survey. Retrieved 3 March 2012.
  4. ^ "Landslides". California Geological Survey. Retrieved 3 March 2012.
  5. ^ "Forest and Watershed Geology Program". California Geological Survey.
  6. ^ Beuter, Thomas. "A brief history of the Ocean Shore Railroad". San Francisco Trains. Retrieved 3 March 2012.
  7. ^ Ellen, S.D.; Wieczorek, G.F. (1988). "Landslides, floods, and marine effects of the storm of January 3–5, 1982, in the San Francisco Bay region, California" (PDF). U.S. Geological Survey Professional Paper 1434.
  8. ^ Smith, T.C.; Hart, E.W. (July 1982). "Landslides and related storm damage, January 1982, San Francisco Bay region". California Geology. 35 (7): 139–152.
  9. ^ Jones, Donna (January 6, 2012). "Devastating disaster: Storm of 1982 left 22 dead, many more homeless". Santa Cruz Sentinel.
  10. ^ Jibson, Randall W. (2005). "Landslide Hazards at La Conchita, California". U.S. Geological Survey Open File Report 05-1067. Retrieved 3 March 2012.

External links

2005 La Conchita landslide

On January 10, 2005, a major landslide occurred in the town of La Conchita, California. The landslide killed 10 people, and destroyed or damaged dozens of houses. The landslide occurred on part of a previous landslide that occurred in 1995. The historic slides are part of the larger Rincon Mountain slide, which "started many thousands of years ago and will continue generating slides in the future."

2018 Southern California mudflows

A series of mudflows occurred in Southern California in early January 2018, particularly affecting areas northwest of Los Angeles in Santa Barbara County. The incident was responsible for 23 deaths, although the bodies of two victims were not found. Approximately 163 people were hospitalized with various injuries, including four in critical condition. The disaster occurred one month after a series of major wildfires. The conflagrations devastated steep slopes, which caused loss of vegetation and destabilization of the soil and greatly facilitated subsequent mudflows. The mudflows caused at least $177 million (2018 USD) in property damage, and cost at least $7 million in emergency responses and another $43 million (2018 USD) to clean up.

2018 in the United States

This is a list of events in the year 2018 in the United States.

California State Route 1

State Route 1 (SR 1) is a major north–south state highway that runs along most of the Pacific coastline of the U.S. state of California. At a total of just over 659 miles (1,061 km), it is the longest state route in California. SR 1 has several portions designated as either Pacific Coast Highway (PCH), Cabrillo Highway, Shoreline Highway, or Coast Highway. Its southern terminus is at Interstate 5 (I-5) near Dana Point in Orange County and its northern terminus is at U.S. Route 101 (US 101) near Leggett in Mendocino County. SR 1 also at times runs concurrently with US 101, most notably through a 54-mile (87 km) stretch in Ventura and Santa Barbara counties, and across the Golden Gate Bridge.

The highway is designated as an All-American Road. In addition to providing a scenic route to numerous attractions along the coast, the route also serves as a major thoroughfare in the Greater Los Angeles Area, the San Francisco Bay Area, and several other coastal urban areas.

SR 1 was built piecemeal in various stages, with the first section opening in the Big Sur region in the 1930s. However, portions of the route had several names and numbers over the years as more segments opened. It was not until the 1964 state highway renumbering that the entire route was officially designated as SR 1. Although SR 1 is a popular route for its scenic beauty, frequent landslides and erosion along the coast have caused several segments to be either closed for lengthy periods for repairs, or re-routed inland.

Devil's Slide (California)

Devil's Slide is a coastal promontory in California, United States. It lies on the San Mateo County coast between Pacifica and Montara.

Franciscan Assemblage

Franciscan Assemblage or Franciscan Complex is a geologic term for a late Mesozoic terrane of heterogeneous rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was named by geologist Andrew Lawson, who also named the San Andreas fault that defines the western extent of the assemblage.Easily identified by its red-green color (sometimes dark blue) and folded, twisted appearance, the assemblage is usually characterized as being primarily metamorphic in nature. Its most well-known rocks are serpentine and blueschists. However, the assemblage contains a wide range of different rocks in different stages of the rock cycle. A single outcrop may contain basalt, chert, and other rocks in addition to schist.

The outcrops of the formation have a very large range, extending from Douglas County, Oregon to Santa Barbara County, California. Franciscan-like formations may be as far south as Santa Catalina Island. The formation lends its name to the term describing high-pressure regional metamorphic facies, the Franciscan facies series.


The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as a heavy rainfall, an earthquake, a slope cut to build a road, and many others), although this is not always identifiable.

List of landslides

This list of landslides is a list of notable landslides and mudflows divided into sections by date and type. This list is very incomplete as there is no central catalogue for landslides, although some for individual countries/areas do exist. Volumes of landslides are recorded in the scientific literature using cubic kilometres (km3) for the largest and millions of cubic metres (normally given the non-standard shortening of MCM) for most events.

Ruth A. M. Schmidt

Ruth Anna Marie Schmidt (April 22, 1916 – March 29, 2014) was an American geologist and paleontologist who was a pioneer for women scientists. She spent most of her career in Alaska, where she established a United States Geological Survey (USGS) field office and established the first Department of Geology at the Anchorage Community College, now part of the University of Alaska Anchorage. In 1964, Schmidt directed the initial assessment of the damage done to the city of Anchorage by the Great Alaska Earthquake, the largest earthquake in North American history, and the second largest earthquake ever to be recorded. She worked for the USGS in Washington, DC during the era of McCarthyism and was investigated twice for disloyalty because of her membership in the interracial Washington Cooperative Bookshop. She was cleared both times. She earned a number of awards, honors, and letters of commendation and appreciation. After her death in 2014, she was recognized as a philanthropist.

The Sunken City

In 1929 a natural landslide caused several beachside homes in the Point Fermin area of the San Pedro neighborhood of Los Angeles to slide into the ocean. The site was dubbed “Sunken City”. The development of cliffside homes and exclusive bungalows was established in the 1920s by George Peck to attract people who wanted to live with a beautiful view of the Pacific Ocean. Experts investigating the landslide said that the ground was shifting at a rate of 11 inches per day. The landslide occurred at the southern tip of San Pedro sending nearly 40,000 square feet of land into the Pacific Ocean.The first reports of damage occurred on January 2, 1929, a waterline broke underneath the Ocean View Inn hotel on Paseo Del Mar, and a few days later a gas line broke under the same building. Most of the houses on the 600 block of Paseo Del Mar were evacuated and relocated before the collapse. There was not enough time to move two houses, which ultimately slid into the ocean. Part of the adjoining Point Fermin Park also fell. The slide displaced houses, commercial buildings, streets, and sidewalks.

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