1996 Yosemite Valley landslide

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1996 Yosemite Valley Landslide
1996 Yosemite Valley rockslide.jpg
Aftermath of the landslide
DateJuly 10, 1996 (1996-07-10)
Location Yosemite Valley, YNP, Mariposa County, CA, United States
Coordinates 37°43′44″N119°33′40″W / 37.729°N 119.561°W / 37.729; -119.561 Coordinates: 37°43′44″N119°33′40″W / 37.729°N 119.561°W / 37.729; -119.561
Cause162,000 tons of debris fell at speeds of up to 160 mph [1]
Deaths1

The 1996 Yosemite Valley landslide occurred on July 10, 1996, near the Happy Isles trailhead in Yosemite Valley, Yosemite National Park, Mariposa County, California. 162,000 tons of rocks and other debris fell to the ground at over 160 miles per hour. Of the 12 campers /hikers involved in the incident, one was killed. The landslide competes with the 1997 Merced River flood and the 2013 Rim wildfire for the designation of the worst natural disaster in Yosemite to date. (start new writer} I was at a Lower River camp site, about one mile away from Happy Isles. The earthquake caused by the rock slide was followed almost immediately by a sonic boom. Soon afterward a granite dust mushroom cloud formed over Happy Isles. The immense pressure created at the base of the rock slide blew down giant pine trees as if they were nothing. A young man camped next to me rode his bicycle immediately to Happy Isles and took pictures which he sold to the Fresno Bee. Afterwards the nearby campground tables and trees were covered with a thick coat of granite dust . About 35 TV trucks were parked in the valley the following days. {end}

Contents

Impacts

At 6:52 pm PDT Wednesday, July 10, 1996, a large block of granite, with an estimated volume of 78,000 cubic yards, detached from the cliff between Washburn Point and Glacier Point, in Yosemite Valley.

UC Berkeley Seismograph Station [2]

The first impact occurred at 18:52:28.0 Pacific Daylight Time (02:52:28 UTC), and the second at 18:52:41.6 PDT (02:52:41 UTC).

After detaching from the cliff, the rock mass slide [ sic ] down a rock shelf for 600 feet at an angle of 50 degrees from vertical and acquired sufficient speed to free-fall ballistically an estimated 1800 feet (550 m) prior to impacting about 200 feet (60 m) from the base of the cliff in the Happy Isles area of the valley floor in Yosemite National Park (field investigation with Gerald Wieczorak and Richard Waitt).

UC Berkeley Seismograph Station [2]

Effects

One of the impacts killed a hiker near the cliffs.

The force of the impacts was comparable to a 2.15-magnitude earthquake. [2] The impacts also triggered the formation of a massive dust cloud. One witness [3] "noted that the sky went black for six minutes as the dust raised by the cloud blocked out the late afternoon light." The rock fall also caused the uprooting or damage of about 1,000 trees in the immediate blast zone. [3] Structures damaged by the snapping of these trees included the Happy Isles Nature Center, a snack bar, and a bridge. [4] On the day of the incident, the park was hosting as many as 20,000 visitors. [5]

See also

Related Research Articles

Yosemite National Park National park in California, United States

Yosemite National Park is an American national park in Northern California, surrounded on the southeast by Sierra National Forest and on the northwest by Stanislaus National Forest. The park is managed by the National Park Service and covers an area of 748,436 acres and sits in four counties: centered in Tuolumne and Mariposa, extending north and east to Mono and south to Madera County. Designated a World Heritage Site in 1984, Yosemite is internationally recognized for its granite cliffs, waterfalls, clear streams, giant sequoia groves, lakes, mountains, meadows, glaciers, and biological diversity. Almost 95% of the park is designated wilderness.

Yosemite Valley Glacial valley in California, United States

Yosemite Valley is a glacial valley in Yosemite National Park in the western Sierra Nevada mountains of Central California. The valley is about 7.5 miles (12 km) long and approximately 3000–3500 feet deep, surrounded by high granite summits such as Half Dome and El Capitan, and densely forested with pines. The valley is drained by the Merced River, and a multitude of streams and waterfalls flow into it, including Tenaya, Illilouette, Yosemite and Bridalveil Creeks. Yosemite Falls is the highest waterfall in North America and is a big attraction especially in the spring, when the water flow is at its peak. The valley is renowned for its natural environment and is regarded as the centerpiece of Yosemite National Park, attracting visitors from around the world.

Geology of the Yosemite area

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

Mist Trail

The Mist Trail is one of the most popular short hikes in Yosemite National Park, California, USA. The steep hike follows the Merced River, starting at Happy Isles in Yosemite Valley, past Vernal Fall and Emerald Pool, to Nevada Fall.

Merced River River in California

The Merced River, in the central part of the U.S. state of California, is a 145-mile (233 km)-long tributary of the San Joaquin River flowing from the Sierra Nevada into the San Joaquin Valley. It is most well known for its swift and steep course through the southern part of Yosemite National Park, where it is the primary watercourse flowing through Yosemite Valley. The river's character changes dramatically once it reaches the plains of the agricultural San Joaquin Valley, where it becomes a slow-moving meandering stream.

Happy Isles

Happy Isles is a group of small isles in the Merced River in Yosemite National Park, California, USA. They are located at the easternmost end of the Yosemite Valley floor. This scenic spot is the starting point for the Mist Trail, and is also the northern trailhead for the John Muir Trail. Happy Isles is also the trailhead for popular hiking destinations along the Mist Trail and Half Dome.

Nevada Fall

Nevada Fall is a 594-foot (181 m) high waterfall on the Merced River in Yosemite National Park, California. It is located below the granite dome, Liberty Cap, at the west end of Little Yosemite Valley. The waterfall is widely recognized by its "bent" shape, in which the water free-falls for roughly the first third of its length to a steep slick-rock slope. This mid-fall impact of the water on the cliff face creates a turbulent, whitewater appearance in the fall and produces a great deal of mist which covers a wide radius, which led to its current name.

Glacier Point Viewpoint above Yosemite Valley, in California, USA

Glacier Point is a viewpoint above Yosemite Valley in the U.S. state of California. It is located on the south wall of Yosemite Valley at an elevation of 7,214 feet (2,199 m), 3,200 feet (980 m) above Curry Village. The point offers a superb view of several of Yosemite National Park's well-known landmarks, including Yosemite Valley, Yosemite Falls, Half Dome, Vernal Fall, Nevada Fall, and Clouds Rest. Between 1872 and 1968, it was the site of the Yosemite Firefall.

History of the Yosemite area History of the Sierra Nevada region of California

Human habitation in the Sierra Nevada region of California reaches back 8,000 to 10,000 years ago. Historically attested Native American populations, such as the Sierra Miwok, Mono and Paiute, belong to the Uto-Aztecan and Utian phyla. In the mid-19th century, a band of Native Americans called the Ahwahnechee lived in Yosemite Valley. The California Gold Rush greatly increased the number of non-indigenous people in the region. Tensions between Native Americans and white settlers escalated into the Mariposa War. As part of this conflict, settler James Savage led the Mariposa Battalion into Yosemite Valley in 1851, in pursuit of Ahwaneechees led by Chief Tenaya. The California state military forces burned the tribe's villages, destroyed their food stores, killed the chief's sons, and forced the tribe out of Yosemite. Accounts from the Mariposa Battalion, especially from Dr. Lafayette Bunnell, popularized Yosemite Valley as a scenic wonder.

Vernal Fall

Vernal Fall is a 317-foot (96.6 m) waterfall on the Merced River just downstream of Nevada Fall in Yosemite National Park, California. Like its upstream neighbor, Vernal Fall is clearly visible at a distance, from Glacier Point, as well as close up, along the Mist Trail. The waterfall flows all year long, although by the end of summer it is substantially reduced in volume and can split into multiple strands, rather than a single curtain of water.

Clouds Rest

Clouds Rest is a mountain in Yosemite National Park east northeast of Yosemite Village, California. Although there are many peaks in the park having far greater elevation, Clouds Rest's proximity to the valley gives it a very high degree of visual prominence.

Little Yosemite Valley Valley in Mariposa County, California

Little Yosemite Valley is a smaller glacial valley upstream in the Merced River drainage from the Yosemite Valley in Yosemite National Park. The Merced River meanders through the 3.5 mi (5.6 km) long flat valley, draining out over Nevada Fall and Vernal Fall before emptying into the main Yosemite Valley. It can be reached by a day hike from the main valley, and is the most popular area in the Yosemite Wilderness. The Valley provides access to nearby destinations such as the back side of Half Dome, Clouds Rest and the High Sierra Camp at Merced Lake.

Geography of the Yosemite area

Yosemite National Park is located in the central Sierra Nevada of California. Three wilderness areas are adjacent to Yosemite: the Ansel Adams Wilderness to the southeast, the Hoover Wilderness to the northeast, and the Emigrant Wilderness to the north.

The Pywiack Cascade is a waterfall in Yosemite National Park within the U.S. state of California. It is located a few miles downstream from the outlet of Tenaya Lake on Tenaya Creek at the head of the steep and rugged granite gorge, Tenaya Canyon. The waterfall can be viewed from Glacier Point, or by a 6-mile (9.7 km) hike from Olmsted Point, but the canyon is dangerous and the waterfall is unsafe to be reached on foot. The waterfall is highly seasonal. It typically rages in the spring and early summer while shrinking to a trickle by late summer to mid-autumn.

1997 Merced River flood

The January 1997 flood of the Merced River occurred from December 31, 1996, to January 5, 1997, throughout the Yosemite Valley in Yosemite National Park, Mariposa County, California, US. The flood stands as arguably the park's worst natural disaster to date, and inarguably the worst flood in park history. The Merced River at Happy Isles peaked at 10,100 cubic feet per second during the flood. A book was written on the flood later in 1997 by Mark Goodin titled Yosemite: The 100-Year Flood.

Yosemite Valley Bridges United States historic place

The Yosemite Valley Bridges are eight bridges in the Yosemite Valley of Yosemite National Park, most of them spanning the Merced River. Five of them were built in 1928, with the remainder built between 1921 and 1933. The bridges feature a concrete structure faced with local stone, in an elliptical or three-centered arch configuration. They are notable for their uniform character and for their conformance to tenets of the National Park Service rustic style. Design work for the seven newer bridges was by George D. Whittle of the San Francisco District Office of the U.S. Bureau of Public Roads for the National Park Service. Concrete bridges were chosen at the urging of Thomas Chalmers Vint of the Park Service, in lieu of alternative designs for steel truss bridges, or suspension bridges suggested by the park superintendent.

High Sierra Camps

The High Sierra Camps are nine rustic lodging facilities located in two national parks and a national monument in California's Sierra Nevada mountain range. Open most years from June or July to September, they are staffed camps with tent cabins and food service facilities. The backcountry camps receive their supplies by pack mules.

Ferguson landslide

The Ferguson landslide, also commonly called the Ferguson Slide, is an active landslide in the Merced River canyon in the U.S. state of California which in 2006 blocked a primary access road to Yosemite National Park. The slide still blocked the original road as of early 2020, although temporary bridges allow one-way traffic around the slide and into the park. The slide is a natural phenomenon, and resulted from the erosion dynamics of the river valley.

Panorama Trail

The Panorama Trail is a marked hiking trail in Yosemite National Park that descends along the south wall of Yosemite Valley from Glacier Point, past several major waterfalls, to Happy Isles. The trail derives its name from the panoramic vistas visible along the route, most notably Panorama Point.

References

  1. Appalachian Long Distance Hikers Association|ALDHA Landslide at Yosemite
  2. 1 2 3 Robert Uhrhammer (December 10, 1996). "The Yosemite Rock Fall of July 10, 1996". berkeley.edu. Retrieved December 29, 2013.
  3. 1 2 Wieczorek, Gerald F.; Snyder, James B.; Waitt, Richard B.; Morrissey, Meghan M.; Uhrhammer, Robert A.; Harp, Edwin L.; Norris, Robert D.; Bursik, Marcus I.; Finewood, Lee G. (2000). "Unusual July 10, 1996, rock fall at Happy Isles, Yosemite National Park, California" (PDF). Geological Society of America Bulletin. 112 (1): 75–85. doi:10.1130/0016-7606(2000)112<0075:ujrfah>2.3.co;2.
  4. Morrissey M. M. (1999). "Air blasts generated by rockfall impacts: Analysis of the 1996 Happy Isles event in Yosemite National Park". Journal of Geophysical Research: Solid Earth. 104: 23189–23198. Bibcode:1999JGR...10423189M. doi: 10.1029/1999JB900189 .
  5. Stephen Schwartz & Teresa Moore (July 11, 1996). "Huge Rock Slide in Yosemite – 1 Killed / Several Injured as slab plunges into Happy Isles area". San Francisco Chronicle . Retrieved December 29, 2013.