Half Dome

From Encyclopedia Jr, free information reference for Kids

Half Dome
Half Dome from Yosemite Valley
Elevation	8,836 ft (2,693 m)
Location	California, USA
Range	Sierra Nevada
Prominence	1,360 ft (414 m)
Coordinates	37°44′45.6″N, 119°31′59.4″W
Topo map	USGS Half Dome
Type	Granite dome
Age of rock	Cretaceous, 93 Myr
First ascent	1875 by George G. Anderson
Easiest route	cable route

Half Dome is a granite dome at the eastern end of Yosemite Valley, possibly the Valley's most familiar sight. The granite crest rises more than 4,737 feet (1,440 m) above the Valley floor.

As late as the 1870s, Half Dome was considered completely unclimbable, but it may now be ascended in several different ways. Thousands of hikers reach the top each year by following a trail from the valley floor. The trailhead is only two miles from Half Dome itself, but the circuitous route is 8.5 miles (13.5 kilometres) long. The final ascent is accomplished by following a pair of metal cables raised on posts up the peak's steep but somewhat rounded east face. The cable route was constructed in 1919.

Alternatively, over a dozen rock climbing routes lead from the valley up Half Dome's vertical northwest face. Other routes ascend the south face and the west shoulder. The first route climbed was the Regular Northwest Face route - originally climbed in 1957 by Royal Robbins, Mike Sherrick, and Jerry Gallwas. This 5-day ascent was the first Grade VI climb in the United States.

Half Dome is nearly as whole as it ever was. The impression from the valley floor that this is a round dome which has lost its northwest half is an illusion. From Glacier Point or from Washburn Point, Half Dome can be seen as a thin ridge of rock oriented northeast-southwest, with its southeast side almost as steep as its northwest side except for the very top. Although the trend of this ridge, as well as that of Tenaya Canyon, is probably controlled by master joints, 80 percent of the northwest “half” of the original dome may well still be there. What probably happened is that frost splitting of the rock at the back of a tiny glacier against Half Dome above Mirror Lake gradually quarried back the steep northwest face. As the base of the cliff was hewn away, ultimately parts of the sheets parallel to the original upper surface of Half Dome were left projecting outward at the crest of the vertical cliff.

An image of Half Dome, along with John Muir and the California Condor, appears on the California State quarter, released in January, 2005.

Half Dome was originally called "Tis-sa-ack," meaning Cleft Rock in the dialect of the local Native Americans. Tis-sa-ack is also the name of the fourth route on the formation, ascended by Royal Robbins and Don Peterson over eight days in October, 1969.

Half Dome is included in many company and organization logos, including that of the environmental group, the Sierra Club.

[edit] Hiking the Cables Route

Half Dome, showing the valley and surrounding area.

The Half Dome Cables Route hike is 8.5 miles from the valley floor to the top with 4,800 feet of elevation gain. The length and difficulty of the trail make it less crowded than many other park trails, but on long summer days there can still be quite a crowd on top. The trail climbs past Vernal and Nevada Falls, then continues into Little Yosemite Valley, then north to the base of the northeast ridge of Half Dome itself. The final 900 feet (275 m) of ascent are up the rock, and between two cables used as handholds.

Hikers use cables to ascend Half Dome

The hike can be done from the valley floor in one long day, or many people break it up by camping in Little Yosemite Valley. The cables are put in place in late May, and removed for the winter in early October. Gloves are recommended for the cable climb, as are proper conditioning, sufficient water and food, and caution to be exercised when there are any thunderclouds in the sky.

Depending on the time of day, the cables can be crowded and some climbers turn back due to fear. The top of Half Dome is a large, flat area where many people can relax and enjoy their accomplishment. The summit offers views of the surrounding areas, including Little Yosemite Valley and the Valley Floor. A notable location to the side of Half Dome is the Diving Board, where Ansel Adams took his photograph, "Monolith, The Face Of Half Dome (1926)."

[edit] External links

• Half Dome hike on the NPS website
• Geologic Story of Yosemite National Park by N. King Huber, USGS (adapted PD source)
• Half Dome on TierraWiki.org
• Half Dome on Summitpost.org
• Hiking Half Dome Report
• Hiking Half Dome on OutdoorDB.org
• Daily updating time-lapse movies of Half Dome
• Maps and aerial photos
  • WikiSatellite view at WikiMapia
  • Topographic map from TopoZone
  • Aerial image from TerraServer-USA
  • Surrounding area map from Google Maps
  • Location in the United States from the Census Bureau