Ahwiyah Point rockfall

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gstock

climber
Yosemite Valley
Topic Author's Original Post - Mar 29, 2009 - 11:09pm PT
FYI

A very large rock fall occurred from Ahwiyah Point near Half Dome at 5:26 am on the morning of March 28. The rock fall originated near the summit of Ahwiyah Point and fell roughly 1800 feet to the floor of Tenaya Canyon, striking ledges along the way. Debris extended well out into Tenaya Canyon, knocking down hundreds of trees and burying the southern portion of the Mirror Lake loop trail. Reminiscent of the 1996 Happy Isles rock fall, there appears to have been a small airblast associated with impact on the valley floor. Fortunately, due to the event occurring in the early morning, there were no injuries. The impact generated ground shaking that was recorded by numerous seismometers across California, registering as the equivalent of a local magnitude 2.5 earthquake:

http://quake.wr.usgs.gov/recenteqs/Quakes/nc40233925.htm

The volume of the Ahwiyah Point rock fall is still being determined, but it was clearly one of the largest rock falls in the past decade; for perspective this rock fall was many times the size of the recent October 2008 rock falls behind Curry Village. Numerous smaller rock falls have occurred from Ahwiyah Point since the initial failure, and the southern portion of the Mirror Lake loop trail remains closed until further notice.

Greg Stock
Park Geologist
(209) 379-1420
greg_stock@nps.gov
Gary Carpenter

climber
SF Bay Area
Mar 29, 2009 - 11:18pm PT
Thanks for the info. Greg.
Dapper Dan

climber
Menlo Park
Mar 29, 2009 - 11:19pm PT
COOL !

can't wait to see some pics

glad no one was hurt .

I wonder if it was in the vicinity of hidden falls?
neebee

Social climber
calif/texas
Mar 29, 2009 - 11:20pm PT
hey there... say, thanks for the info... i dont get up there, naturally, but i like to keep in touch... as some much family and childhood connection has been there for me...

thanks for sharing, as the climbers sure can use updates...
Lynne Leichtfuss

Social climber
valley center, ca
Mar 29, 2009 - 11:33pm PT
So what does all this movement over the past year mean in the big picture......Predictions for the next several years ? lrl
Doug Robinson

Trad climber
Santa Cruz
Mar 29, 2009 - 11:34pm PT
Thanks Greg. We are sure benefitting -- our community -- from you being on board with timely info, accuracy and interpretation. Much appreciated.

It's exciting when our so-solid Valley turns once again from place to process.
Ed Hartouni

Trad climber
Livermore, CA
Mar 30, 2009 - 12:59am PT
Walleye, did you get the dates right?
also, not clear what I'm looking at in the photos...

Finally, I guess I should reconsider the climbs on the obscurity list over there.

[edit] I see it now in the background... thanks!
gstock

climber
Yosemite Valley
Topic Author's Reply - Mar 30, 2009 - 11:57am PT
Wow, these posts get buried fast! Bump for geology in action.

Lynne, based on detailed volume calculations of the talus beneath Yosemite's cliffs, all of which has accumulated in the past 17,000, there is little evidence to support the perception that rock fall rates are increasing. What has increased is our ability to record, document, and communicate these events.

As far as predictions, I predict there will be more rock falls.

Greg

cleo

Social climber
Berkeley, CA
Mar 30, 2009 - 12:30pm PT
Thanks Greg -

Is there access to Snow Creek Trail?

-Val
JEleazarian

Trad climber
Fresno CA
Mar 30, 2009 - 12:31pm PT
Wow! I'd actually had the Harding/Merry route on my tick list of obscurities (See, Ed, you aren't the only one hunting these things!). I guess I'd better reconsider.

John
Dick_Lugar

Trad climber
Indiana (the other Mideast)
Mar 30, 2009 - 12:33pm PT
Old lines die and new lines are born...
Capt.

climber
some eastside hovel
Mar 30, 2009 - 01:12pm PT
Thanks for the info Greg.Glad to see you're still over there.I'm looking you up next time I'm on that side.Once again,thanks for keepin' us posted.

Kirk Sager

PS-When we doin' Swiss Arete?
Chris McNamara

SuperTopo staff member
Mar 30, 2009 - 01:14pm PT
i put this on the homepage

http://www.supertopo.com
tom woods

Gym climber
Bishop, CA
Mar 30, 2009 - 01:55pm PT
meanwhile the locals are busy with new first ascents on the boulders.

Seriously, a big ol' rock came down by the folly around 1999, landed square in the middle of the road. It had multiple new routes on it with in a day. Then the road crew blew it up.
SteveW

Trad climber
The state of confusion
Mar 30, 2009 - 02:12pm PT
Holy kiboly!
That's amazing--and it's incredible but wonderful that
no one was in the area and/or hurt, killed, etc.
Jaybro

Social climber
wuz real!
Mar 30, 2009 - 03:11pm PT
I have it on pretty good authority tht the whole thing is going to collapse, Lynne. wish I could name my sources...



=)
scuffy b

climber
4 to 8
Mar 30, 2009 - 03:16pm PT
There was a nice avalanche just east of Widow's Tears on
Saturday. I heard another earlier but didn't see it.

Adamame

Trad climber
El Portal
Mar 30, 2009 - 04:23pm PT
I climbed the Column on the 26th and arrived on Dinner Ledge a few hours after the rockfall. A few friends witnessed it earlier that morning from the ledge. They said it looked like fireworks! As the rocks disintegrate I guess they spark. Rocks continued to fall all weekend and we also witnessed a fireworks show from the Dinner Ledge Viewing area during the next night.
gunsmoke

Trad climber
Clackamas, Oregon
Mar 30, 2009 - 04:35pm PT
Here's a rebalanced version of Walleye's before/after pictures:
Gary

climber
Desolation Basin, Calif.
Mar 30, 2009 - 04:40pm PT
Paging Juan de Fuca, paging Mr. Juan de Fuca...
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