Discussion Topic Return to Forum List This thread has been locked Messages 1 - 11 of total 11 in this topic gstock



climber Yosemite Valley Topic Author's Original Post - Jan 21, 2015 - 09:07am PT Yosemite Rockfall Year in Review: 2014



Despite near-record dry conditions, 2014 was an active year for rockfalls in Yosemite. In all, there were 77 documented rockfalls, which is considerably more than the recent (2006-2013) average of about 45 rockfalls per year. Most of the rockfalls in 2014 were relatively small, with a total volume of about 6,500 cubic meters (about 19,350 tons).



The largest rockfall of 2014 occurred at 1:30 pm on March 31 from the north wall of Hetch Hetchy valley near Wapama Falls. This rockfall had a volume of roughly 5,000 cubic meters (about 14,880 tons). Rock debris buried a 120 meter-long section of the Rancheria Trail along the north shore of the reservoir, necessitating a multi-week closure while the trail was rebuilt. The second largest rockfall of 2014 occurred at about 4:30 am on the morning of June 11, when a 450 cubic meter (1340 ton) block fell from the southeast face of El Capitan near Horsetail Falls. The block fragmented on impact, creating a large dust cloud that lingered in western Yosemite Valley for more than an hour.



The most consequential rockfall of 2014 occurred at 8:15 pm on June 29, when a rock slab of about 215 cubic meters (about 640 tons) fell from the east wall of Indian Canyon. Although nobody was in this remote area at the time, a segment of the communications cable running up Indian Canyon was destroyed, cutting off all phone communications to White Wolf and Tuolumne Meadows. The cable was replaced by a microwave transmitter.



Perhaps the most important rockfall of 2014 was also one of the smallest. At 3:22 am on the morning of February 11, a rockfall of approximately 15 cubic meters (about 45 tons) occurred in the vicinity of Staircase Falls above Curry Village. Previous rockfalls in 2003 and 2007 damaged cabins, caused injuries, and prompted evacuations. In contrast, the February 11, 2014 rockfall was hardly noticed because cabins there were removed in late 2013 following a comprehensive assessment of rockfall hazard and risk ( http://pubs.usgs.gov/sir/2014/5129/ ). One boulder landed within the footprint of a former cabin. This event, described in a short publication, ( http://onlinelibrary.wiley.com/doi/10.1002/2014EO290002/pdf ), demonstrated the merit of removing buildings from hazardous areas.



Other areas in Yosemite experiencing rockfalls in 2014 include Yosemite Falls, Royal Arches, LeConte Gully, and the Merced River Gorge; these latter rockfalls were related to the Dog Rock Fire in early October.



It is very likely that there were additional rockfalls in 2014, but these events either were not witnessed or went unreported. However, the significant increase in the number of small rockfalls in 2014 suggests more thorough reporting of rockfalls (and likely not a real increase in small rockfalls). If you witness a rockfall of any size, encounter fresh rock debris, or hear cracking or popping sounds emanating from the cliffs, please contact park geologist Greg Stock at 209/379-1420 or by email at greg_stock@nps.gov, or contact Park Dispatch by dialing 911 within the park. Documented rockfalls are added to the park database ( http://pubs.usgs.gov/ds/746/ ), enabling evaluation of rockfall activity to improve public safety. Tork



climber Yosemite Jan 21, 2015 - 09:12am PT Thanks Greg! Hope you all are doing well.



Jeff micronut



Trad climber Fresno/Clovis, ca Jan 21, 2015 - 09:33am PT Great information. Thank you Greg.



Scott Vitaliy M.



Mountain climber San Francisco Jan 21, 2015 - 10:08am PT Thank you for taking the time to share this. Under Achiever



Trad climber Los Angeles Jan 21, 2015 - 12:20pm PT Excellent summary. Thanks for taking the time to put this up.



So the good news...Glacier Point Apron was rockfall-free in 2014? cleo



Social climber wherever you go, there you are Jan 21, 2015 - 12:41pm PT Thanks Greg! Good to hear from you, as always! JEleazarian



Trad climber Fresno CA Jan 21, 2015 - 12:56pm PT Thank you, Greg, for your continuing and very helpful reports.



John c wilmot



climber Jan 21, 2015 - 01:45pm PT Is the mirror lake loop trail open? I wonder if all the work I put in under an active rockfall zone was worth it? Still upset that the trail crew I was on was ordered to work in a zone that NO OTHER NPS official in a position of authority was willing- and that was hit with rockfall a year after we worked there(from an obviously dangerous and loose hanging block). I wonder why they have a geologist if they are going to put NPS workers in highly active rockfall zones- that the park knew was a major hazard? gstock



climber Yosemite Valley Topic Author's Reply - Jan 21, 2015 - 02:30pm PT The Mirror Lake loop trail is open.



Anyone interested in learning more about our rockfall studies in Yosemite, including the challenges of assessing rockfall potential, is welcome to contact me anytime.



Greg Stock

Yosemite Park Geologist

(209) 379-1420

greg_stock@nps.gov le_bruce



climber Oakland, CA Jan 21, 2015 - 03:05pm PT At 3:22 am on the morning of February 11, a rockfall of approximately 15 cubic meters (about 45 tons) occurred in the vicinity of Staircase Falls above Curry Village ... One boulder landed within the footprint of a former cabin.

Damn! Good work by whoever made the decision to shut down/move those tents... Were you in those talks, Greg? WBraun



climber Jan 21, 2015 - 03:25pm PT When those big rockfalls happened at Curry Village we got sent over there to search possible victims.



Early the next morning another one cuts loose and we go over there again.



After some time later they can't decide whether to shut down the whole curry village or what because Greg is up on El Cap climbing the mescalito

I believe it was and he was the guy who's supposed to decide right then and there what to do at that moment in time.



Lober comes over after we're done searching again and says;

"Get your sh!t! we're going up to the top of El Cap and we're pulling Greg off the climb and bringing him back here to make a decision".



LOL, ... Poor Greg got yarded off the wall .....



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