what is the landslide type of the la conchita?

3G). Translational slide: In this type of slide, the landslide mass moves along a roughly planar surface with little rotation or backward tilting (fig. Entrapped snow and ice may also help mobilize such flows, but the unqualified term avalanche is generally used to refer only to an avalanche of snow. [2] It lies on a narrow strip of land about 250 meters (820 feet) wide between the shoreline and abutting a 180-meter (590ft) high bluff. Inspection of the site within a few hours of the landslide indicated that much of the deposit consisted of fairly dry material (James O'Tousa, RJR Engineering, personal commun., 2005). Omissions? As discussed above, the 1995 landslide was relatively deep and primarily moved as a coherent slumpearth flow. From December 27, 2004, through January 10, 2005, the nearby city of Ventura received 378 millimeters (14.9 inches) of rainfall, only slightly less than its mean annual total of 390 millimeters (15.4 inches). This is a typical type of landslide. Toppling failures are distinguished by the forward rotation of a unit or units about some pivotal point, below or low in the unit, under the actions of gravity and forces exerted by adjacent units or by fluids in cracks (fig. What mitigation took place after the La Conchita slide? Morton, D.M., 1971, Seismically triggered landslides above San Fernando Valley: California Geology, v. 24, no. 4, p. 2224. In the 1909 slide, a train was buried. Below is a summary of reports and maps to identify hazards associated with different types of landslides in this part of the state. A block slide is a translational slide in which the moving mass consists of a single unit or a few closely related units that move downslope as a relatively coherent mass (fig. In some instances, for example in many newspaper reports, mudflows and debris flows are commonly referred to as mudslides.. https://www.britannica.com/science/landslide, Geology.com - Landslide Hazard Information. Study with Quizlet and memorize flashcards containing terms like A comprehensive term for any type of downslope movement of Earth materials is, What strategy has been suggested to stabilize the La Conchita, California, landslide?, In Yosemite National Park, strong bedrock influences the formation of what types of hillslopes? Where did the La Conchita . Landslides are generally classified by type of movement (slides, flows, spreads, topples, or falls) and type of material (rock, debris, or earth). Photo taken March 8, 1995. The deposit covered approximately 4 hectares (9.9 acres), and the volume was estimated to be approximately 1.3 million cubic meters (1.7 million cubic yards) of sediment. While this preliminary report does not represent a detailed evaluation of those hazards, a few reasonable observations can be made. Movement is caused by shear stress sufficient to produce permanent deformation, but too small to produce shear failure. NOAA uses this information to provide early warning for debris flows in areas affected by the fire. In both 1889 and 1909, the Southern Pacific rail line running along the coast was inundated. OF 05-1067, "La Conchita Ranch is sold for $2.5 million", "La Conchita Lawsuit Settled, But It's Not Over", "Settlement reached in La Conchita lawsuit", Assessing Landslide Hazard Over a 130-Year Period for La Conchita, California, https://en.wikipedia.org/w/index.php?title=La_Conchita_landslides&oldid=1134048066, 2005 natural disasters in the United States, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, The 2005 La Conchita landslide is the setting of, This page was last edited on 16 January 2023, at 19:34. Although it is not uncommon for subsidiary debris flows to occur from the toes or scarps of existing landslides (Morton and Campbell, 1989), that is not what happened in 2005. Explain why. Rock of both formations is very weakly cemented and has been regionally associated with extensive landslide activity (Morton, 1971; Harp and Jibson, 1995, 1996; Parise and Jibson, 2000). The 2005 landslide occurred on part of a previous landslide that occurred in 1995. Contact between the flowing mass and the underlying material can be distinct, or the contact can be one of diffuse shear. Photo by R.L. 2) On figure 2, label the following: main scarp, head of slide, body of slide, toe of slide. 1 What type of slide is the La Conchita slide? There are five basic categories of flows that differ from one another in fundamental ways. Figure 8 shows an aerial photograph of La Conchita taken in September 2004. 7). What was different about the 2005 slide at La Conchita compared to the 1995 slide in the same place? Do they actually do gymnastics in Make It or Break It? Maps displaying where shallow landslides are most likely to occur are based on observation of previous landslide activity, topographic slope, and information on the bedrock material (seePreliminary soil-slip susceptibility maps, southwestern California-Open-File Report 2003-17). 12). Coastal cliff failuresmay also occur simply as a result of heightened precipitation as well wave action makes cliffs inherently unstable, and rainfall may be the ultimate trigger for failure, even during times with little to no wave action. The La Conchita landslide then occurred on March 4. In 2005, an additional landslide occurred at the end of a 15day period of near-record rainfall levels. Separation occurs along discontinuities such as fractures, joints, and bedding planes, and movement occurs by free-fall, bouncing, and rolling. On January 10, 2005, the southeastern portion of the 1995 landslide deposit failed, resulting in shallow, rapid fluid flow, unlike the 1995 landslide. O'Tousa, James, 1995, La Conchita landslide, Ventura County, California: Association of Engineering Geologists AEG News, v. 38, no. The latter landslide killed 10 people, and destroyed or damaged dozens of houses. These schematics illustrate the major types of landslide movement. The video shows relatively intact vegetation being rafted on the surface of the rapidly flowing mass, which indicates that much of the landslide mass simply was being carried on the fluidized layer at depth, which presumably was much more saturated. Since that time, other slides have occurred, covering at times cultivated land, roadways, and the community itself.[4]. This was a wholesale remobilization of a significant portion of the 1995 deposit. Articles from Britannica Encyclopedias for elementary and high school students. 13, 52 p. National Oceanic and Atmospheric Administration, 1995b, Climatological dataCalifornia, JanuaryMarch 1995: National Climatic Data Center, v. 99, no. Earthflow: Earthflows have a characteristic "hourglass" shape (fig. Of primary interest to the general public and various Governmental entities is the current state of hazard at La Conchita. An increase in water content, resulting from either natural causes or human activity, typically weakens sandy materials through the reduction of interparticle friction and weakens clays through the dissolution of interparticle cements, the hydration of clay minerals, and the elimination of interparticle (capillary) tension. What year did the landslide happen in Ventura CA? La Conchita, coastal area of southern California. Coarse particles such as sand grains have high frictional strength but low cohesive strength, whereas the opposite is true for clays, which are composed of fine particles. . Wofford, Michael, 2005, Ventura, California weather conditions. The developed part of the slope where the houses were impacted has a flatter slope, and so the flow probably slowed to no more than 5 m/s (15 ft/s) in the neighborhood. Types of mass movement Flows are a mixture of water, rock and sediment. Actually there have been several sizes, types, and ages of landslides. 3A). Landslides are a type of "mass wasting" which denotes any down slope movement of soil and rock under the direct influence of gravity. 9). Over time, upslope ponding of water by such back-tilted blocks can enlarge the area of instability, so that a stable condition is reached only when the slope is reduced to a very low gradient. The 1995 slide was 120 m (400 ft) wide, 330 m (1100 ft) long, and covered approximately 4 ha (10 acres). The slope material liquefies and runs out, forming a bowl or depression at the head. The various types of landslides can be differentiated by the kinds of material involved and the mode of movement. The landslide area was approximately 350 m (1,150 ft) long and 80100 m (260330 ft) wide. Background rates of coastal cliff erosion are variable along the California coast (seeNational Assessment of Shoreline Change Part 4: Historical Coastal Cliff Retreat along the California Coast - Open File Report 2007-1133) and tied to the rock or soil strength of the cliffs among other factors, but these measurements of historic coastal cliff retreat provide indications of places most susceptible to coastal landslides. 1995 and 2005, La Conchita, California: On March 4, 1995, a fast-moving earthflow damaged nine houses in the southern California coastal community of La Conchita. 5 and 6). There is also a need for a comprehensive analysis of cliff retr. The project engages emergency planners, businesses, universities, government agencies, and others in preparing for major natural disasters. During the winter season in California, beaches typically erode thereby allowing waves to reach further inland and to inundate the bottoms of coastal cliffs. The 2005 landslide was a shallower remobilization of the very same material into a rapid, highly fluid debris flow that buried 10 . The lush, green vegetation visible in the southeastern (lower right in photograph) part of the 1995 deposit clearly indicates that drainage on and within the 1995 landslide deposit concentrated water in the part of the mass that failed in 2005. Below are other science projects associated with this project. Several smaller, more recent slumps and earth flows also are visible, as is the 1995 slumpearth flow (terminology after Varnes, 1978). What kind of mitigation was done after the La Conchita landslide? Three years after the 2005 landslide, the owners of an avocado ranch agreed to turn over all 700 acres (280ha) of their land and other assets to settle the suit. On January 10, 2005, a landslide struck the community of La Conchita in Ventura County, California, destroying or seriously damaging 36 houses and killing 10 people. The 2005 landslide mobilized the south flank of a larger landslide that occurred in March 1995, and destroyed 9 homes. In this report, empirical models are used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year rainstorm for the 2013 Springs fire in Ventura County, California. Types of Landslides The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. Since that time, landslides frequently have inundated roads, railroads, cultivated land, and more recently, the La Conchita community. Other classification systems incorporate additional variables, such as the rate of movement and the water, air, or ice content of the landslide material. What was the type of landslide in recent 2005 La Conchita landslide? The 1995 landslide was a deep, coherent slumpearth flow that deformed plastically and moved slowly enough that people could get out of its way. A landslide can be defined as follows: [T]he movement of a mass of rock, debris, or earth down a slope. Figure 2. A wall built after the 1995 landslide to keep minor landslide debris off the road was tilted forward and(or) overtopped in places by debris from the 2005 landslide (fig. Back scarp of ancient landslide Scarp of small recent landslide 1995 landslide Figure 2: Close-up image of the 1995 landslide event at La Conchita, CA. Incipient movement of the upper part of the slide was reported as early as the summer of 1994, when surface cracks were observed in the upper part of the slope (O'Tousa, 1995). The deep mode of failure in 1995 is consistent with this delay: deeper landslides commonly are triggered by deep infiltration of rainfall, which can take weeks or months to occur (for example, Morton and Campbell, 1989). The events of Jan. 10, 2005, when 400,000 tons of mud slid down the bluff behind La Conchita, killing seven adults and three children, are frozen in the eerie tableau a reminder of the hidden dangers lurking beneath the surface. 3F). There are generally three types of creep: (1)seasonal, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; (2) continuous, where shear stress continuously exceeds the strength of the material; and (3) progressive, where slopes are reaching the point of failure as other types of mass movements. Hemphill, J.J., 2001, Assessing landslide hazard over a 130year period for La Conchita, California, in Association of Pacific Coast Geographers Annual Meeting, Santa Barbara, Calif., September 1215 2001. In low-relief areas, landslides occur as cut-and-fill failures (roadway and building excavations), river bluff failures, lateral spreading landslides, collapse of mine-waste piles (especially coal), and a wide variety of slope failures associated with quarries and open-pit mines. The landslide scenarios sketched above potentially could impact any part of the La Conchita community. The landslide killed 10 people, and destroyed or damaged dozens of houses. Agenda What is a landslide? Deep-seated landslides can be triggered by deep infiltration of rainfall, which can take weeks or months to occur. La Conchita is a small Pacific coastal community that lies between Santa Barbara, CA and Ventura, CA. Some, but not all, of the major winter storms that have caused landslide fatalities and property damage in southern California have occurred during El Nio (1997-98 info) conditions. Reported landslides began in 1865. The storm of March 23 also may have played a role in triggering initial movement of the hillside, which already was approaching instability due to longerterm seasonal rises in groundwater levels. Answer-Based on the observation from the figure. When was the last landslide in La Conchita? Get a Britannica Premium subscription and gain access to exclusive content. The movement near the head of the slide is largely downward, exposing a steep head scarp, and movement within the displaced mass takes place along internal slip planes, each tending to tilt backward. Figure 1: Air photo of La Conchita, CA taken in 2002. Schuster. [6] Earthflow: Earthflows have a characteristic hourglass shape (fig. Other hazards, such as flash floods and debris flows, now become the focus. La Conchita is located on the southern California coastline midway between Ventura and Santa Barbara (fig. The arcuate bench at the top of the bluff is the head of a very large prehistoric landslide that affected the entire bluff. Accessibility StatementFor more information contact us atinfo@libretexts.org. Such a failure scenario, involving a significant amount of dry material that fully mobilized on a saturated layer, indicates that most of the rain that fell on the surface of the 1995 deposit did not infiltrate but drained off the surface. This is a typical type of landslide. We also use third-party cookies that help us analyze and understand how you use this website. This is a typical type of landslide. Some are triggered by earthquakes, but more frequently landslides are caused by intense and/or prolonged rainfall. I estimate from viewing the video that high on the slope, the landslide was moving perhaps 10 m/s (30 ft/s). Near a Slope? The 2005 La Conchita landslide occurred at about 12:30 p.m. on January 10. Landslides are described and classified in various ways depending upon the material (s) involved, mode of movement, rate of movement, and the water, air or ice content of the landslide material (see Figure 4). Some, but not all, of the major winter storms that have caused landslide fatalities and property damage in southern California have occurred duringEl Nio(1997-98 info) conditions. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. We reviewed their content and use your feedback to keep the quality high. 13, 60 p. National Oceanic and Atmospheric Administration, 1994b, Climatological dataCalifornia, OctoberDecember 1994: National Climatic Data Center, v. 98, nos. In La Conchita, there was a landslide and earthflow in the spring of 1995 (see figure 1). The two major types of slides are rotational slides and translational slides. What about the remaining 1995 deposit? The landslide destroyed 13 houses and severely damaged 23 others. The material moves as a single mass along a slippery zone. The La Conchita landslide in Ventura County is an example of a deep-seated landslide that has experienced both styles of movement (seeLandslide Hazards at La Conchita, California- Open-File Report 2015-1067). At the time of our visit (January 14, 2005) water was still issuing from the base of the main landslide scarp and was ponding at several locations on the 2005 deposit (fig. This information provides tools to help make PDF files accessible. When coherent material, either bedrock or soil, rests on materials that liquefy, the upper units may undergo fracturing and extension and may then subside, translate, rotate, disintegrate, or liquefy and flow. This indicates that the landslide material, although it flowed rapidly, was quite viscous and pushed structures in front of it rather than flowing around them or filling them with mud, as sometimes occurs with fully saturated debris and mud flows. 3I). Unfortunately, we currently lack the understanding to accurately forecast what might happen in each possible rainfall scenario. This type of movement can subsequently cause the mass to fall or slide. How and why the same material failed twice in 10 years by fundamentally different mechanisms certainly will be the object of future research, and it is much too complex to analyze in detail at this time. Actually there have been several sizes, types, and ages of landslides. The cookie is used to store the user consent for the cookies in the category "Performance". 2). A translational slide is sometimes called a mud slide when it occurs along gently sloping, discrete shear planes in fine-grained rocks (such as fissured clays) and the displaced mass is fluidized by an increase in pore water pressure. The content on this page is copyrighted under a Creative Commons Attribution 4.0 International license. Creep: Creep is the imperceptibly slow, steady, downward movement of slope-forming soil or rock. Major types of landslide movements. A spread is the complex lateral movement of relatively coherent earth materials resting on a weaker substrate that is subject to liquefaction or plastic flow. What was the type of landslide in recent 2005 La Conchita landslide? Landslides in the United States occur in all 50 States. Jibson, R.W., 1989, Debris flows in southern Puerto Rico, in Schultz, A.P., and Jibson, R.W., eds., Landslide Processes in Eastern North America and Puerto Rico: Geological Society of America Special Paper 236, p.2955. 1). An idealized slump-earth flow showing commonly used nomenclature for labeling the parts of a landslide. In some instances, for example in many newspaper reports, mudflows and debris flows are commonly referred to as "mudslides.". The U.S. Geological Survey, Multi Hazards Demonstration Project (MHDP) uses hazards science to improve resiliency of communities to natural disasters including earthquakes, tsunamis, wildfires, landslides, floods and coastal erosion. Many readers will be familiar with the La Conchita landslide in California. The landslide occurred on part of a previous landslide that occurred in 1995. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. Debris flows include <50% fines. Currently, we have insufficient data and understanding of the failure mechanisms of this landslide to adequately answer these questions, but it is clear that the hazard from renewed landslide movement is considerable. You also have the option to opt-out of these cookies. People were evacuated and the houses nearest the slide were completely destroyed. Figure 1: Air photo of La Conchita, CA taken in 2002. The 2005 event in La Conchita was a deep-seated landslide, which is characterized as 10-15 ft. deep. Photo by R.L. As coastal populations continue to grow and community infrastructures are threatened by erosion, there is increased demand for accurate information regarding trends and rates of coastal cliff retreat. People were evacuated and the houses nearest the slide were completely destroyed. Although many types of mass movements are included in the general term landslide, the more restrictive use of the term refers only to mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material. The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". On January 10, 2005, a landslide struck the community of La Conchita in Ventura County, California, destroying or seriously damaging 36 houses and killing 10 people. Often referred to as "mudflows," debris flows are a type of landslide made up of a rapidly moving mixture of dirt, rocks, trees, and water (and sometimes ash) that start on a hillside and travel downvalley. Days later, on March 10, a subsequent debris flow from a canyon to the northwest damaged five additional houses in the northwestern part of La Conchita. 4). This cookie is set by GDPR Cookie Consent plugin. Examine Figure 1 (an oblique air photo of the slide features on the coast at La Conchita), Figure 2 (a close-up view of the. LockA locked padlock The dominant mode of movement is lateral extension accompanied by shear or tensile fractures. 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. In 1995, the community experienced a major slide, which damaged and destroyed a significant portion of the community. This was not the first destructive landslide to damage this community, nor is it likely to be the last. 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What type of mass wasting took place in La Conchita? Historical accounts dating back to 1865 have reported landslides in the area around La Conchita as being a regular occurrence (Hemphill, 2001).
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what is the landslide type of the la conchita? 2023