Yosemite, Half Dome, hiking trail, rock slide, Mirror Lake

Yosemite’s Popular Mirror Lake Loop Hiking Trail Reopens; Closed in 2009 by Massive Rock Slide

Saturday, October 20 2012 14:20   Trails
Closed for more than three years due to a massive rock slide that took place just below Half Dome, Yosemite National Park in California reopened the Mirror Lake Loop hiking trail to the public on Oct. 18, 2012.

The five-mile loop that follows Tenaya Creek around Mirror Lake in Yosemite Valley had been closed since March 28, 2009 due to a rockfall from Ahwiyah Point so large that it generated ground shaking equivalent to a magnitude 2.4 earthquake.

ahwiyah_trail_pa140826To prepare for the reopening, Yosemite trail crews constructed a new trail on the edge of the talus slope near Tenaya Creek. Work consisted of removing trees and rock in order to create new trail alignment.

Several blasting operations took place over the past several weeks in order to remove large pieces of granite from the trail corridor and create new material for retaining walls and trail construction. Rangers said that even with the reopening of the hiking trail, crews will be present over the next several days to complete the work.

The slide was massive. Rocks fell approximately 1,800 feet to the floor of Yosemite Valley from Ahwiyah Point, knocking down hundreds of trees and burying hundreds of feet of the trail on the southern portion of the loop.

The rockfall was estimated to be approximately 43,000 cubic meters, or 115,000 tons. No injuries or structures were affected by the rockfall. The Ahwiyah Point rockfall is the largest rockfall documented in Yosemite National Park since the Middle Brother rockfall event in 1987.

Because of the most recent rockfall activity around Yosemite Valley, there has been speculation that rockfall has become more frequent.

ahwiyah_damageBased on historical databases and recent events, park geologists are unable to discern a geologically significant increase in rockfall activity in Yosemite Valley.

Rockfalls are a natural and dynamic geologic process, rangers said. Due to its steep, glacier-carved cliffs, Yosemite Valley experiences many rockfalls each year. Natural processes like rockfall help to create the beautiful and changing scenery in Yosemite National Park.

For more information about Yosemite, visit the park's Website at
www.nps.gov/yose .


Related Articles