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. The neighborhood of La Conchita has suffered from large landslides in the recent past that have wiped out homes and even killed people. The USGS has a long history of research to identify landslide hazards in southern California (seeSouthern California LandslidesAn Overview- Fact Sheet 2005-3107). 1 it is 1). The 2005 landslide pushed many of the houses off their foundations and into each other at the toe of the landslide (figs. 3G). Figure 3. Geol 1014 Chapter 10 Flashcards | Quizlet The upper part of the slope consists of interlayered siliceous shale, siltstone, and sandstone of the Middle to Upper Miocene Monterey Formation. Legal. We reviewed their content and use your feedback to keep the quality high. The term "landslide" encompasses events such as rock falls, topples, slides, spreads, and flows. Figure 1 shows a graphic illustration of a landslide, with the commonly accepted terminology describing its features. Fires that denude slopes of vegetation intensify the susceptibility of slopes to debris flows. In both 1889 and 1909, the Southern Pacific rail line running along the coast was inundated. 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). This information provides tools to help make PDF files accessible. British Geological Survey - What is a landslide? A summary of recent and past landslides and debris flows caused by rainfall in Southern California. 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. Rockslides and other types of slides involve the displacement of material along one or more discrete shearing surfaces. Although rainfall intensities were not extreme, moderate to highintensity rainfall persisted for more than 2 weeks, and the landslide occurred at the culmination of this 15day highrainfall period (fig. 1012. 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.. Where did the La Conchita . 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). This cookie is set by GDPR Cookie Consent plugin. What type of slide is the La Conchita slide? The two major types of slides are rotational slides and translational slides. The volume of the landslide was estimated to be approximately 200,000 cubic meters with a surface 350 meters (1,150 feet) long and 80100 meters (260330ft) wide. The 2005 landslide involved few new materials and seems to have been a continuation of the original 1995 landslide. 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. Wave energy is also typically higher during the winter, and particularly during El Nio events, thereby exacerbating the potential for coastal erosion. The entrance to La Conchita is from the northbound lanes of Hwy 101. We also use third-party cookies that help us analyze and understand how you use this website. Based on the opinion that surface water infiltration from irrigation contributed to the landslide, seventy-one homeowners sued La Conchita Ranch Co. in Bateman v. La Conchita Ranch Co. The plaintiffs also sued the County of Ventura for damages, claiming that a wall that the County built at the base of the landslide caused or contributed to the landslide. 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. 5 What was different about the 2005 slide at La Conchita compared to the 1995 slide in the same place? 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. Do they actually do gymnastics in Make It or Break It? The dominant mode of movement is lateral extension accompanied by shear or tensile fractures. 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? [2] The dimensions of the slides were approximately 120 meters (390 feet) wide, 330 meters (1,080ft) long, and 30 meters (98ft) deep. What experience do you need to become a teacher? The volume of the landslide was estimated to be approximately 200,000 cubic meters with a surface 350 meters (1,150 feet) long and 80100 meters (260330 ft) wide. The Southern Pacific rail line that extends along the coastal strip was inundated by landslide debris in 1889 and again in 1909, when a train also was buried (Hemphill, 2001). What was different about the 2005 slide at La Conchita compared to the 1995 slide in the same place? 3F). 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. 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. A few things, however, can be said. 3J). Omissions? The 1995 landslide was a deep, coherent slumpearth flow that deformed plastically and moved slowly enough that people could get out of its way. 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 1995 landslide), and Figure 3 (some common types oflandslides). The 1995 landslide was a deep, coherent slumpearth flow that deformed plastically and moved slowly enough that people could get out of its way. This is a typical type of landslide. 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. Types of landslides Factors contribute to landslides Landslide in Utah. An official website of the United States government. The material moves as a single mass along a slippery zone. 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. 7 What happened in the La Conchita landslide 2005? 4, p. 2224. The already loosened sediment from the 1995 landslide made the 2005 event a lot more catastrophic. 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. Corrections? Morton, D.M., and Campbell, R.H., 1989, Cyclic landsliding at Wrightwood, southern California, in Sadler, P.M., and Morton, D.M., eds., Landslides in a semiarid environment with emphasis on the inland valleys of southern California: Inland Geological Society, Riverside, Calif., v. 2, p. 174182. Wofford, Michael, 2005, Ventura, California weather conditions. This was not the first destructive landslide to damage this community, nor is it likely to be the last. Rotational slide: This is a slide in which the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide (fig. 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. 3H). 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. cleared that the landslide was a slump type., A) La Conchita, California The community of La Conchita in Ventura County, California experiences frequent landslides. [5] The Ranch was found 50% negligent because it did not provide for adequate drainage of its orchards during torrential rains and settled the suit. PDF Falling Into the Pacific: California Landslides and Land Use Controls 9). This was not the first destructive landslide to damage this community, nor is it likely to be the last. Secure .gov websites use HTTPS Mudflow. People were evacuated and the houses nearest the slide were completely destroyed. 7). Future landslide activity could occur in the areas of the 1995 and 2005 landslides or in other areas and could damage or destroy any or all of the developed area. A) La Conchita, California The community of La Conchita in Ventura County, California experiences frequent landslides. At Ventura (20 km [12 mi] southeast of La Conchita) seasonal antecedent rainfall from October 1, 2004 through January 10, 2005 totaled 493 mm (19.4 in) as compared to the mean value of 122 mm (4.8 in). A large section of the hillside slid down and buried several homes after receiving almost 30 inches of rain that winter. A lock () or https:// means youve safely connected to the .gov website. How can the hazards of landslides to humans be mitigated? Various processes that weaken the shear strength of a slope may also activate landslides. The two formations are in fault contact along the active Red Mountain Fault, which extends across the slope face. Some materials with a loose, open sediment fabric will weaken if they are mechanically disturbed or flooded with water. Bits of rock fall off the cliff face, usually due to freeze-thaw weathering. The La Conchita area has experienced, and will likely continue to experience, a rather bewildering variety of landslide hazards. This cookie is set by GDPR Cookie Consent plugin. Landslides can also be activated by processes that weaken the shear strength of a slopes material. In La Conchita, there was a landslide and earthflow in the spring of 1995 (see figure 1). This apparently resulted from a highly hazardous situation involving a twophased landslide mechanism: (1) a saturated, highly fluid layer at depth on which the landslide mobilized that (2) carried a thick layer of drier, much more viscous material that effectively acted as a battering ram. Rockfall. Lateral spreading in fine-grained materials on shallow slopes is usually progressive. 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. { "10.01:_Why_It_Matters" : "property get [Map MindTouch.Deki.Logic.ExtensionProcessorQueryProvider+<>c__DisplayClass228_0.
Ramsgate To Sandwich Coastal Walk,
Coastguard Call Outs Today,
Stephen Pearcy Parents,
Class Of 2025 Basketball Rankings,
Baseball Acronyms Explained,
Articles W
what is the landslide type of the la conchita?