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gstock
climber
Yosemite Valley
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Topic Author's Original Post - Jan 10, 2014 - 12:54pm PT
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Another relatively quiet year for rockfalls in Yosemite. Thanks to all of you who reported events this year.
Yosemite Rockfall Year in Review: 2013
Following the trend of the previous two years, 2013 was a quiet year for rockfalls in Yosemite. In all, there were 34 documented rockfalls, which is well below the recent (2006-2012) average of about 55 documented rockfalls per year. The cumulative rockfall volume was about 1500 cubic meters (about 4460 tons), also well below average. Given that 35% of rockfalls occurring since 1857 were associated in some way with precipitation (rain or snowmelt), the fact that 2013 was arguably the driest year on record for California may explain the relatively low level of rockfall activity.
The two most consequential rockfalls in Yosemite in 2013 impacted trails. The first occurred early on the morning of May 11 when a block about 320 cubic meters in volume (about 950 tons) fell from the top of the Panorama Cliff and landed on the John Muir Trail below Clark’s Point. Rock debris covered about 500 meters (about 1600 feet) of switchbacks, and the trail was closed for several weeks while damaged walls were repaired and the trail cleared.
The second consequential rockfall occurred at about 5 am on the morning of October 5 when a block of about 735 cubic meters (about 2200 tons) fell from Ahwiyah Point north of Half Dome; this was the largest rockfall of 2013. Ahwiyah Point experienced a very large rockfall in 2009 and has had intermittent activity since then. The rockfall on October 5 occurred from the same location as the 2009 event, and also curiously occurred at the same time of day. This early morning timing, combined with the fact that it occurred during the government shutdown, ensured that there were no injuries associated with the rockfall. The Mirror Lake Loop trail, recently reopened after extensive repairs following the 2009 event, experienced some minor damage from boulder impacts. This trail was also closed for several weeks while the source area was monitored and the trail cleared.
Other areas in Yosemite experiencing rockfalls in 2013 include Middle and Higher Cathedral Rocks, the Porcelain Wall west of Half Dome, Glacier Point, Royal Arches, and El Capitan.
It is very likely that there were additional rockfalls in 2013, but these events either were not witnessed or went unreported. 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/ ), which enables evaluation of rockfall activity to help improve public safety.
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mucci
Trad climber
The pitch of Bagalaar above you
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Jan 10, 2014 - 01:05pm PT
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Thanks Greg!
Cool to hear about the ones we miss.
I watched 2 significant releases directly above the "Cow" on Glacier Point this year.
Each had a fairly large impact zones.
People on the Grack were gripped out of their minds.
If you don't mind, what dates do you have listed for the Glacier Point rockfall? The link is broken above.
Thanks for the choss update.
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Mungeclimber
Trad climber
Nothing creative to say
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Jan 10, 2014 - 01:33pm PT
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Yosemite is way dangerous.
Maybe Pinnacles Mucci? LOL
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Jan 10, 2014 - 01:58pm PT
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Hey Josh, I may have missed those rockfalls from above the Cow. For 2013 I have rockfalls from Glacier Point occurring on January 25 (5 pm), March 22 (9 pm), March 31 (4:30 pm), April 24-25 (late pm/early am) and June 26 (6 am). None of those sound like likely candidates for the rockfalls you observed (?). If you could possibly track down the dates and give me a brief description I'll include them in the database.
Also, I fixed the link above, sorry about that. Note that the published database extends to 2011.
Greg
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mucci
Trad climber
The pitch of Bagalaar above you
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Jan 10, 2014 - 02:09pm PT
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Greg-
Thanks for the reply, I will look at my notes and get the dates for you.
These are my best guess of the release points, I had a view from about 300yds climbers left.
It is possible the rockfalls were a bit left of the cow. I may have a picture taken after the event, and be able to compare it to xrez 2008.
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BooDawg
Social climber
Butterfly Town
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Jan 10, 2014 - 03:01pm PT
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Hi Greg,
I heard a rockfall from the Ahwahnee Hotel grounds that sounded like it came from the Rhombus Wall-Ahwahnee Buttress area. I looked for dust thru the trees but couldn't see any. I was leading a tour, so I couldn't investigate further. I meant to write you, but...
It would have been in August, about 3-4 p.m. Not a large volume judging from the sounds. Sorry I can't be of more help.
Ken
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gstock
climber
Yosemite Valley
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Topic Author's Reply - Jan 10, 2014 - 04:17pm PT
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Thanks Ken. I have a report from July 29, 4:40 pm from the Rhombus Wall/Royal Arches area. It was reported by Ahwahnee staff who heard rockfall sounds but did not see a dust cloud. Maybe this is same event you witnessed?
Greg
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BooDawg
Social climber
Butterfly Town
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Jan 10, 2014 - 04:30pm PT
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Hi Greg, I'll bet it's the same event! Glad you got more precise data! Anyone walk up later to look for its precise location and volume?
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