The lower part of the slope is siltstone, sandstone, and mudstone of the Pliocene Pico Formation (O'Tousa, 1995). 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. If people continue to live in La Conchita, more lives will . 10 years after fatal mudslide, tiny La Conchita accepts the risks These schematics illustrate the major types of landslide movement. Earth materials can become detached from a steep slope without significant shearing, fall freely under gravity, and land on a surface from which they bounce and fall farther. 2) On figure 2, label the following: main scarp, head of slide, body of slide, toe of slide. February 1995 produced only about onethird of the normal rainfall, but a modest storm on March 23 produced 21 mm (0.81 in) of rain. 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. 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. La Conchita landslides - Wikipedia 1 What type of slide is the La Conchita slide? Figure 3: Some major types of mass movements. Language links are at the top of the page across from the title. What type of mass wasting took place in La Conchita? La Conchita (1995) La Conchita landslide, Ventura County. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Of primary interest to the general public and various Governmental entities is the current state of hazard at La Conchita. The 2005 landslide was a shallower remobilization of the very same material into a rapid, highly fluid debris flow that buried 10 . La Conchita Landslide: Case History and Remedial Measures Spreads occur as the result of liquefaction caused by water saturation or earthquake shock in such substrates as loess, a weakly cemented wind-lain silt. During and just after storms, existing coastal landslides may become reactivated and seemingly stable coastal cliffs may erode and fail rapidly. La Conchita, coastal area of southern California. The entrance to La Conchita is from the northbound lanes of Hwy 101. There are five basic categories of flows that differ from one another in fundamental ways. People were evacuated and the houses nearest the slide were completely destroyed. Casualties in the United States are primarily caused by rockfalls, rock slides, and debris flows. La Conchita ( / l kntit / ( listen); Spanish for "The Little Shell") is a small unincorporated community in western Ventura County, California, on U.S. Route 101 just southeast of the Santa Barbara county line. Debris flows also commonly mobilize from other types of landslides that occur on steep slopes, are nearly saturated, and consist of a large proportion of silt- and sand-sized material. What was different about the 2005 slide at La Conchita compared to the 1995 slide in the same place? Short-term stresses, such as those imposed by earthquakes and rainstorms, can likewise contribute to the activation of landslides. Landslide. 3J). The costliest landslide in U. history occurred in the Thistle, Utah area in April 1983. The landslides in the area around La Conchita have been a regular occurrence, according to the historical accounts dating back to 1865. I estimate from viewing the video that high on the slope, the landslide was moving perhaps 10 m/s (30 ft/s). A few things, however, can be said. Although landslides are primarily associated with mountainous regions, they can also occur in areas of generally low relief. Shear stresses can be built up within a slope by a number of processes. The slope material liquefies and runs out, forming a bowl or depression at the head. The tragedy came 10 years after the hill collapsed in 1995 when nine homes were lost. [2] The dimensions of the slides were approximately 120 meters (390 feet) wide, 330 meters (1,080ft) long, and 30 meters (98ft) deep. There are four different types of mass movement: The landslide, which occurred about 130 km northwest of Los Angeles, California, mobilized over 40,000 cubic yards of wet debris into a large scale debris flow (commonly referred to in the media as a mudslide) that flowed into a residential community at the foot of the slope, killing 10 persons and damaging or . U.S. Department of the Interior | U.S. Geological Survey Wave energy is also typically higher during the winter, and particularly during El Nio events, thereby exacerbating the potential for coastal erosion. La Conchita is a small Pacific coastal community that lies between Santa Barbara, CA and Ventura, CA. The La Conchita landslide then occurred on March 4. This cookie is set by GDPR Cookie Consent plugin. On January 10, 2005, a major landslide occurred in La Conchita. c) Slides: A slide is the downslope movement of a soil or rock mass occurring dominantly on the surface of rupture or relatively thin zones of intense shear strain. There were 10 confirmed fatalities. 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. 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 volume of material moved by the landslide was 2.8 cubic kilometers (0.67 mi 3) . The content on this page is copyrighted under a Creative Commons Attribution 4.0 International license. 2023 California Landslide Response A type of landslide in which the distribution of particle velocities resembles that of a viscous fluid is called a flow. Expansion of man-made developments into fire-prone wildlands has created situations where wildfires can destroy lives and property, as can the flooding and debris flows that are common in the aftermath of the fires. Where did the La Conchita . Note the numerous landslides that have taken place in the area, including the large slide in 1995. The most important fluidizing agent is water, but trapped air is sometimes involved. Previous work at the USGS has identified both the areas of southwestern California most susceptible to shallow landslides and the rainfall conditions required to trigger slope failures. Module 7, Page 7 - Physical Geography Course Hero is not sponsored or endorsed by any college or university. This dynamic tectonic environment has created a spectacular landscape of rugged mountains and steep-walled valleys that compose much of the regions scenic beauty.
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