The 1996 Yosemite Valley

Yosemite Valley

Yosemite Valley is a glacial valley in Yosemite National Park in the western Sierra Nevada mountains of California, carved out by the Merced River. The valley is about long and up to a mile deep, surrounded by high granite summits such as Half Dome and El Capitan, and densely forested with pines...

 landslide

Landslide

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

occurred July 10 1996 near the Happy Isles

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...

 trailhead in Yosemite Valley

Yosemite Valley

Yosemite Valley is a glacial valley in Yosemite National Park in the western Sierra Nevada mountains of California, carved out by the Merced River. The valley is about long and up to a mile deep, surrounded by high granite summits such as Half Dome and El Capitan, and densely forested with pines...

, Yosemite National Park

Yosemite National Park

Yosemite National Park is a United States National Park spanning eastern portions of Tuolumne, Mariposa and Madera counties in east central California, United States. The park covers an area of and reaches across the western slopes of the Sierra Nevada mountain chain...

, Mariposa County, California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

. 162,000 tons of rocks and other debris fell to the ground at over 160 miles per hour. Of 12 campers

Camping

Camping is an outdoor recreational activity. The participants leave urban areas, their home region, or civilization and enjoy nature while spending one or several nights outdoors, usually at a campsite. Camping may involve the use of a tent, caravan, motorhome, cabin, a primitive structure, or no...

/hikers

Hiking

Hiking is an outdoor activity which consists of walking in natural environments, often in mountainous or other scenic terrain. People often hike on hiking trails. It is such a popular activity that there are numerous hiking organizations worldwide. The health benefits of different types of hiking...

 involved in the incident, one was killed. The landslide competes with the January 1997 Merced River flood for the designation of the worst natural disaster

Natural disaster

A natural disaster is the effect of a natural hazard . It leads to financial, environmental or human losses...

 in Yosemite to date.

Details

• Date - July 10, 1996
• Location -   Yosemite Valley
  Yosemite Valley
  Yosemite Valley is a glacial valley in Yosemite National Park in the western Sierra Nevada mountains of California, carved out by the Merced River. The valley is about long and up to a mile deep, surrounded by high granite summits such as Half Dome and El Capitan, and densely forested with pines...
  
  , YNP
  Yosemite National Park
  Yosemite National Park is a United States National Park spanning eastern portions of Tuolumne, Mariposa and Madera counties in east central California, United States. The park covers an area of and reaches across the western slopes of the Sierra Nevada mountain chain...
  
  , Mariposa County, CA
  California
  California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
  
  ,  USA
• Victims - 12
• Fatalities - 1
• Survivors - 11
• Weight of Debris - 162,000 tons
• Speed of Fall - 160+ mph

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

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 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

One of the impacts killed a hiker near the cliffs.