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Slide 1: Landslide Overview Map of the Conterminous United States-reproduced from U.S. Geological Survey Open-file Report 97-289. Different colors denote areas of varying landslide occurrence and susceptibility.
Slide 2: Slide Mountain, Nevada-Boulders partially bury a house from a debris flow triggered by rapid snowmelt in late May 1983. The rapidly moving debris flow emerged from a canyon and killed one person, injured several others, destroyed or severely damaged five homes, and buried a highway. A map delineating geological hazards in this area prepared a decade earlier by the USGS in cooperation with the Nevada Bureau of Mines and Geology identified the hazard zone that was partially inundated by this debris flow. Photograph by U.S. Geological Survey.
Slide 3: The 1983 Thistle landslide at Thistle, Utah-This landslide began moving in the spring of 1983 in response to groundwater buildup from heavy rains the previous September and the melting of deep snowpack for the winter of 1982-83. Within a few weeks the landslide dammed the Spanish Fork River, obliterating U.S. Highway 6 and the main line of the Denver and Rio Grande Western Railroad. The town of Thistle was inundated under the floodwaters rising behind the landslide dam. Total costs (direct and indirect) incurred by this landslide exceeded $400 million, the most costly single landslide event in U.S. history. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 4: The Mamayes, Puerto Rico, landslide, 1985. This landslide destroyed 120 houses and killed at least 129 people, the greatest number of casualties from any single landslide in North America. The catastrophic block slide was triggered by a tropical storm that produced extremely heavy rainfall. Contributing factors could also have included sewage directly discharged into the ground in the densely populated area, and a leaking water pipe at the top of the landslide. Photograph by R.W. Jibson, U.S. Geological Survey.
Slide 5: Rock and snow avalanche, Mount Huascaran, Peru. In 1970, an earthquake-induced rock and snow avalanche on Mt. Huascaran, Peru, buried the towns of Yungay and Ranrahirca. The death toll from the Debris Avalanche was 18,000 (total fatalities from the earthquake and the debris flow was 66,000). The avalanche started as a sliding mass of glacial ice and rock about 3,000 feet wide and one mile long. The avalanche swept about 11 miles to the village of Yungay at an average speed of more that 100 miles an hour. The fast-moving mass picked up glacial deposits and by the time it reached Yungay, it is estimated to have consisted of about 80 million cubic yards of water, mud, and rocks. Photo courtesy of Servicio Aerofotografico Nacional de Peru, 13 June 1970.
Slide 6: Deposits path of the Mt. Huascaran, Peru, rock and snow avalanche. Photo courtesy of Servicio Aerofotografico Nacional de Peru, 13 June 1970.
Slide 7: The Madison Canyon landslide near Yellowstone Park. This landslide occurred after the Hebgen lake earthquake (Richter Scale Magnitude = 7.5) in Montana, in 1959. The earthquake caused a great slide of rock, soil, and trees to fall from the steep south wall of the Madison River Canyon. Twenty-eight people camping in the area were killed as they were overtaken by this 21 million cubic meter mass. The landslide formed a barrier that completely blocked the gorge and the flow of the Madison River, and created a lake.
Slide 8: Earthflow in Cincinnati, Ohio-This slide shows material being removed by highway crew along the Columbia Parkway, Cincinnati, Ohio. Hamilton County, in the metropolitan Cincinnati area, experienced an average annual economic loss of $5.80 per person (1975 dollars) between 1973 and 1978, the highest calculated per capita loss of any municipality in the United States. Photo by Bob Fleming, USGS.
Slide 9: Rockfall deposition, Yosemite National Park, California-On July 11, 1996, at 6:52 p.m. (Pacific Daylight Time), two large rock blocks, with a combined volume of between 23,000 and 38,000 m 3broke away from Glacier Point, near Happy Isles, a popular trailhead and concession stand. The rock disintegrated when it landed, creating an air blast that was so powerful that it flattened as many as 2,000 trees in the area. One person was killed at the concession stand, and 14 people were seriously injured. The dust kicked up from the pulverized rock blocked out the sun and coated tents and recreational vehicles, not unlike ashfall from a volcano. Additional, smaller rock falls occurred later that night and the next morning. Rockfall hazard is a continuing problem at Yosemite, one that the U.S. Geological Survey and the National Park Service are investigating further. Photograph by Edwin Harp, U.S. Geological Survey.
Slide 10: Sinkhole at Winter Park Florida-Sinkholes, although not classified as landslides, are another form of ground subsidence that can happen catastrophically. This sinkhole occurred in 1981, in the time span of one day. The city of Winter Park stabilized and sealed the sinkhole, converting it into an urban lake. This form of subsidence occurs when carbonate layers that lie below the surface dissolve. When the weight of the overlying ground becomes too great, or the dissolved area too large, the surface collapses into the void. These features occur in what is known as karst topography which is common in Florida, Kentucky, Missouri, Pennsylvania, and Tennessee and also occurs in many other places around the world. Photograph by A. S. Navoy
Slide 11: A landslide near McClure Pass, Colorado, in 1994-This area of the Rocky Mountains has chronic problems where roads cross landslide areas. The State has found that the best solution in this case, is to repair the road as it becomes damaged. This car plunged into the landslide in the middle of the night, after the landslide occurred. Fortunately, no one was injured. Photograph by Terry Taylor, Colorado State Patrol.
Slide 12: A house damaged by a mudflow (lahar) along the Toutle River about 25 miles west-northwest of Mount St. Helens. This lahar resulted from the May 18, 1980 eruption of Mount St. Helens. Mudflow height is recorded by mud coatings on tree trunks. Photograph by D. R. Crandell, U.S. Geological Survey.
Slide 13: Melting snow and ice on the north flank of Washington's Mount St. Helens, triggered this lahar (an Indonesian term for a "volcanic debris flow"), which rapidly traveled down the flanks of the mountain with the North Fork of the Toutle River. The melting snow and Ice resulted from the 1982 eruption of Mount St. Helens. Photograph by Tom Casadevall, U.S. Geological Survey.
Slide 14: Roadcut failure near Golden, Colorado-This small landslide on Colorado State Highway 93, a well-traveled road from Golden to Boulder, Colorado began sliding in 1993 and cost federal, state and local governments $4 million to evaluate and remedy. Remedial measures included giant tiebacks holding the slide material into the Precambrian bedrock, together with the construction of an elaborate drainage system within the slide. Photograph by William M. Brown, III, U.S. Geological Survey.
Slide 15: Fire-related debris flows from Storm King Mountain, near Glenwood Springs, Colorado. The following three photographs show the results of debris flows that blocked Interstate-70 during Labor Day weekend, 1994. A very hot and fast-moving wildfire in July of that year on the slopes of Storm King Mountain denuded the slopes of vegetation. An intense rainstorm generated debris flows from material on the burned hillslopes and in the channels between hills. Interstate traffic was disrupted for a day and caused serious delays for emergency vehicles and hospital access, due to the fact that Interstate-70 is the only access route through this part of the Rockies. The Interstate-70 corridor through the Rocky Mountains experiences numerous problems from landslides, debris flows, and rockfalls. Photograph by Jim Scheidt, Bureau of Land Management.
Slide 16: Cleaning up debris-flow material from an off-ramp on Interstate-70 near Glenwood Springs, Colorado. (This September, 1994 event described in previous slide caption). Photograph by Lynn Highland, U.S. Geological Survey.
Slide 17: Photo shows depth of material that flowed down a hillside channel onto Interstate-70, September, 1994. Photograph by Sharon Diehl, U.S. Geological Survey.
Slide 18: Road damage in Zion National Park, Utah from a landslide that occurred in April, 1995. 100 people were stranded for two days in the Zion Park Lodge, because this road was the only access to the lodge. Landslides can damage lifelines as well as block highways, as shown by the damaged sewer line which paralleled the road. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 19: Another view of the Zion Park landslide. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 20: An oblique air photo of the Slumgullion earthflow in the San Juan Mountains, near Lake City, Colorado. This landslide which occurred about 700 years ago, is more than 7 km long, and is still moving, although very slowly. It has been continually studied over the years by the U.S. Geological Survey and others and has provided much technical information on landslide mechanisms. Photograph by D. J. Varnes, U.S. Geological Survey.
Slide 21: La Conchita, California-a small seaside community along Highway 101 south of Santa Barbara. This landslide and debris flow occurred in the spring of 1995. Many people were evacuated because of the slide and the houses nearest the slide were completely destroyed. Fortunately, no one was killed or injured. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 22: La Conchita, California, ground-level view, looking down a road, towards the toe of the slide. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 23: La Conchita, California-damage to a house - Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 24: La Conchita, California-more damage - Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 25: Slide 25 and Slide 26 show effects of landslides and debris flows during the winter storms of February 1996 in the northwestern United States. Areas of highest rainfall intensities were centered along the Oregon-Washington border. Estimates of damage from the floods and landslides exceeded $800 million in Washington and Oregon alone. This slide shows a failed residential development on a hisllside at Chehalis, Washington. Much of the failure occurred in years immediately before 1996. Photograph by R.L. Schuster, U.S. Geological Survey.
Slide 26: Landslide in marine sediments over basalt, extending across Washington State Highway 4, into the Columbia River, west of Stella, Washington. Photograph by R.L. Schuster, U.S. Geological Survey.