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Majid_S
Mountain climber
Bay Area
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Topic Author's Original Post - Aug 28, 2009 - 01:50am PT
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By TRACIE CONE (AP) – 6 hours ago
YOSEMITE NATIONAL PARK — Scientists worked Thursday to determine if a boulder avalanche that forced the closure of a landmark Yosemite lodge was a one-time event or a precursor of more rockslides to come.
The Ahwahnee Hotel remained closed following a series of landslides Wednesday that peppered the storied building's parking lot with boulders — one the size of two SUVs.
There were no injuries but three cars were damaged and the area was covered in a thick layer of gray dust, after the rocks tumbled from Royal Arches, a popular climbing route that towers 1,600 feet above the majestic retreat.
The hotel's 300 guests were immediately evacuated but escorted back to their rooms Wednesday night to collect their belongings, before being put up in hotels outside the park.
"We realize now that the first one may not be the only one. We want to err on the side of safety," said park spokeswoman Kari Cobb.
A park geologist has been studying the stability of the granite face cut by glaciers and erosion to resemble the arches for which it was named, hoping to determine by Friday afternoon if the hotel can reopen or if the avalanche was a prelude to other rockfalls.
"Yosemite is a wild place," Cobb said.
Park scientists say rockfalls seem to have accelerated in recent years and are the most significant force affecting the Yosemite Valley — a spectacular natural wonder that receives more than 3 million visitors a year.
Since 1857, at least 535 rockfalls have killed 14 people and injured 62, more than at any other national park. Only in the last few years has the park hired a full-time geologist to assess risk.
Still the park was caught off guard last year when rocks hit 17 cabins in Curry Village and sent 150 youngsters running for their lives. A month later park officials permanently closed the 233 cabins closest to the base of Glacier Point.
Park policy is to treat rockfalls as part of a potentially larger series of events.
"We know now that we can never predict rockfall," said Cobb. "We can only learn from what we've done in the past and move forward. Even though some visitors will be upset, we can only say that safety is our No. 1 concern."
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nature
climber
Tucson, AZ
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Aug 28, 2009 - 01:55am PT
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if locker could see to read he'd respond...
YER GONNA DIE!!!111666
sorry, was that bad?
Thanks for the post. It'll be interesting to watch how the accelerated mass wasting plays itself out.
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jfailing
Trad climber
A trailer park in the Sierras
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Aug 28, 2009 - 04:08am PT
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Greg Stock, geologist Superman of the Valley, to the rescue!
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Patrick Sawyer
climber
Originally California now Ireland
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Aug 28, 2009 - 04:45am PT
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Only in the last few years has the park hired a full-time geologist to assess risk.
Seems a bit surprising that a full-time geologist for such work is relatively new to the park.
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luggi
Trad climber
from the backseat of Jake& Elwood Blues car
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Aug 28, 2009 - 11:26am PT
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climb now nature...the loose stuff is already down...
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Srbphoto
Trad climber
Kennewick wa
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Aug 28, 2009 - 11:51am PT
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Let me guess...We are going to spend thousands of dollars for a scientist to tell us "yes, there will be more rockfall in Yosemite!" I'll get up in front of the press for a sheep and a six pack and tell them today!
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jstan
climber
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Aug 28, 2009 - 01:30pm PT
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"Park scientists say rockfalls seem to have accelerated in recent years"
We have heard speculations on this before. It would appear, from the above, there is some data supporting it. Greg is an important resource and here on ST we have seen what he brings to the Park.
Props.
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Gunkie
climber
East Coast US
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Aug 28, 2009 - 01:35pm PT
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I just don't want to be on or under the 'Ear' or 'El Cap Spire' when they cut loose.
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Toker Villain
Big Wall climber
Toquerville, Utah
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Aug 28, 2009 - 01:46pm PT
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I'm just imagining the coyote chimneying Texas Flake with his Acme suction booties when it cuts loose,..
Uh,.. Gee,.. a ditch thousands of feet deep AND THERE'S ROCKFALL???
Do tell.
(they don't really need a geologist unless he/she is exceptionally good gazing into a crystal ball.)
Hundreds of recorded rockfalls and barely more than a dozen dead in a crowded valley?
Lucky SOBs I'd say.
(But its Kalifornia; maybe they need a helmet law,..)
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JesseM
Social climber
Yosemite
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Aug 28, 2009 - 08:11pm PT
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I've been up around Virgina Peak, Return Lake while all of this has been going on. Now I'm on my way to Boulder, CO. I still haven't heard anything from Greg Stock...the only person I'd really trust to report something comprehensible about the rockfall this. I'll encourage him to post here when I talk to him.
Jesse
Yosemite Climbing Ranger
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saa
Social climber
SF Bay Area
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Aug 28, 2009 - 08:46pm PT
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Jesse, Greg,
Greg had some decades of data posted on this forum (I think) about 8 months or a year ago. Has the report been written? If yes, could you post a link to it?
Thx
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Mighty Hiker
Social climber
Vancouver, B.C.
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Aug 28, 2009 - 09:01pm PT
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Greg's post to a thread last autumn:
You can download an Excel file of documented rockfalls in Yosemite from 1857 to 2004 here: http://pubs.usgs.gov/of/2003/of03-491/
I have documented all observed rockfalls since 2004, and was originally planning to include them in an updated USGS Open-File Report to be published in 2010. However, given the keen interest in these data I may try to make them available sooner.
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M_LaRiviere
Trad climber
Oakland, CA
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Aug 28, 2009 - 10:59pm PT
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Hi -
I was on the South Face of Leaning Tower on Monday & Tuesday this week. While walking back to our cars in the hotel lot late Tuesday (actually super early Wednesday a.m.), my partner and I heard the thunder / rifle cracks of light (?) rock fall coming from the Royal Arches area. In retrospect, those sounds were probably precursors to the rock fall that hit the parking lot. Is there a number that should be called to report if/when rock fall is observed?
(This was actually the second fall I've been seen this season... I was on the Nose early on the morning of July 3rd and saw fall on the other side of the valley, somewhere left of the Middle Cathedral)
- M.
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neebee
Social climber
calif/texas
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Aug 28, 2009 - 11:15pm PT
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hey there say, thanks for the share...
has the awannee ever been closed before, due to rock fall... i was just curious...
i know that lynda works there... will it stay closed for a while now?...
yep,i did hear about the camp closures before, though....
i was just trying to keep up on the situation...
glad no hikers were hurt...
god bless... take care all...
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camm-it-up
Trad climber
Los Angeles, CA
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Aug 29, 2009 - 11:04am PT
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aww bummer, rich folks can't get their spa treatments in the valley anymore.
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nature
climber
Tucson, AZ
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Aug 29, 2009 - 11:21am PT
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This isn't about the rock fall itself. This is about risk assessment. Do geologist look into crystal balls? Yeah. Do they see anything? No. But this is like with any specialty - if you don't know it well you probably don't understand the nuances. We don't need Greg to tell us if there will be more rock fall. We need him to do an analysis on the situation, do some number crunching, and develop a statistical model of the chances of another huge rock fall before we (they) can allow joe public to re-enter the area.
Data seems to suggest there is an increase in rockfall. Greg will look into that and tell us. But at the end of the day it's a bunch of numbers. And sadly, especially in environmental sciences like geology, your intuition and gut feeling is probably what's correct. But big brother wants crunched numbers and they don't always add up and make sense.
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Tony Bird
climber
Northridge, CA
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Aug 29, 2009 - 12:01pm PT
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most rockclimbers have some hands-on ability to assess the soundness of rock, perhaps as much as your average geologist. i'm with the guy who said that, after the rockfall, that spot is safe now. do they even know the exact spot these ahwahnee rocks came from? if it was a loose, texas flake-type formation, it should be obvious that that danger is past. the rest is a crapshoot--absolutely unpredictable. a "perched" piece of rock could go tomorrow or 50,000 years from now.
i think it's important to know what you don't know, and i don't see that here. rather, they're trying to promulgate the myth that they're in control and taking care of the public. there may be some room for advancing the science of exfoliatory mechanics--not sure it's worth the effort--but i don't see much sophistication yet. can this greg fellow give us a prediction on texas flake? boot flake? the dozens of rim boulders like the one skinner and piana once belayed off? i doubt it. the best advice is to avoid areas of known rockfall--keeler couloir comes to mind--and take your chances elsewhere. i still love to climb on glacier point--occasionally.
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Dr.Sprock
Boulder climber
Sprocketville
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Aug 29, 2009 - 12:15pm PT
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thats john muir pushin those rocks down on the capitalist pig intruders!
yo John!
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Gunksgoer
Trad climber
nj
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Aug 29, 2009 - 01:23pm PT
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Seems like there should be a pretty obvious scar where the rock came from. A sweep of the surrounding cliff area seems like the responsible thing to do and would provide the most reliable answer.
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NewtMan
Trad climber
Redondo Beach, CA
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Aug 29, 2009 - 02:31pm PT
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Sitting at the Curry Village taco bar wednesday, we heard what sounded like thunder and a huge cloud of dust just to the left of the Arches. Two more followed within a few minutes. So glad to hear nobody was hurt. With the forest fire smoking up the valley a day later, it was an "unusual" week in the valley, to be sure! Still got some nice climbing in on the Apron and Open Books, but definitely makes one stop and think...
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Rhodo-Router
Gym climber
looking nervously up at Foresta
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Aug 29, 2009 - 03:31pm PT
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Tony, you're right in that *those* rocks will never fall again. But spontaneous rockfall sites tend to leave a lot of smaller litter behind which is still poised to go- have a look up above the Folly for evidence of this.
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jstan
climber
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Aug 29, 2009 - 03:41pm PT
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Maybe rather than trying to use seismographs they can afix sensitive microphones to the rock. Small battery powered computer to send data by wireless only when a threshold has been exceeded. With a small amount of DRAM the part of the event prior to exceeding the threshold could even be sent. The NPS already has the guy most able to knock together a rig like this. Knowing him he could have five units in place before the end of September.
Hardest part would be experimenting to see what interface gives the best energy transfer with the rock. Also need to select the bandwidth. Piece of cake.
Have to get a highly skilled climber with a lot of experience to take it up on the face for him tho.
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powderdan
Social climber
mammoth lakes
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Aug 29, 2009 - 05:39pm PT
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more boulders!!!!!!!!!!!
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Mighty Hiker
Social climber
Vancouver, B.C.
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Aug 29, 2009 - 05:47pm PT
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If you placed microphones near identified rockfall zones, how would you filter out extraneous noise - snow, ice, and rainfall, and so on?
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TwistedCrank
climber
Ideeho-dee-do-dah-day
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Aug 29, 2009 - 07:48pm PT
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The harmonics of rocks are different than the harmonics of water, ice, rain, snow, etc.
It would be harder filtering out the ambient noise like cars and trucks.
The seismology guys are always trying to snag the signal and bag the noise.
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WBraun
climber
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Aug 29, 2009 - 07:52pm PT
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You don't use microphones to begin with.
You use piezoelectric elements as strain sensors.
Then SCADA to deliver the info.
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cleo
Social climber
Berkeley, CA
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Aug 29, 2009 - 11:09pm PT
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These are all good ideas, btw... microphones, strain sensors, and studying how much flakes are moving. And yes, there are some great folks on NPS staff that I've meet (not just Yosemite). It is partly a matter of getting proposals funded - crossing my fingers!
(Also, I'm fairly confident that we can differentiate rock cracking from snow, ice, etc. Gunshot detectors in major cities are a similar concept).
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jstan
climber
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Aug 30, 2009 - 12:17am PT
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In my lack of practical knowledge that is why I thought picking up sound in the rock would be more sensitve than detecting movement. Piezoelectic sensors could be the best interface. Sound should have a high velocity and where the integrity of the rock is good it should travel long distances. And by using a Fast Fourier Transform signal processing you can filter out all the band widths not germane to the sounds created in the rock.
Sounds like Cleo has been doing this.
Come to think of it oil drillers send pressure waves into the formations and from the reflections figure out what is below just as in ultrasound equipment. When you put a sensor on a face at a sufficient sensitivity you can surely study the time evolution of the reflections and calculate the underlying rock structure. Then if you know that beforehand when there is rock failure you might be able to locate its position, again by looking at the time delays of the reflections.
Not that I know how to do any of this.
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Tom
Big Wall climber
San Luis Obispo CA
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Aug 30, 2009 - 03:30am PT
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The race is on: who's gonna get the FA of the new RA variations????
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Peter Haan
Trad climber
San Francisco, CA
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Aug 30, 2009 - 09:35am PT
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Or for that matter Tom, who will do the FA of the Folly Continuation???
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gstock
climber
Yosemite Valley
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Aug 30, 2009 - 10:55am PT
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Lots to respond to here.
First, Cleo is the best one on the Forum to address how to monitor rock fall "noise", as that is the thrust of her dissertation at UC Berkeley. In addition to seismometers at the Brothers, she had an acoustic sensor set up (in my back yard) for most of the winter and spring, and recorded the Ahwiyah Point rock fall in March. I think there is a lot of potential for combined seismic/acoustic monitoring of rock fall precursors; we are working on that, as are others, but it is still in the experimental phase. Even if a reliable method is developed, the sheer scale of Yosemite Valley will make monitoring beyond site-specific areas challenging.
I don’t claim to be able to predict exactly when and where rock falls will occur. In some cases, including a few events here in Yosemite, geologists have warned of imminent rock falls that did in fact occur. Usually these situations involved obvious changes such as cracking sounds, propagating fractures, etc. In other cases these “obvious” changes have not produced rock falls, even ten years later. Over half of the documented rock falls in Yosemite Valley do not have recognized triggers, meaning that we cannot say with certainty exactly what triggered the rocks to detach from the cliff. This is true even in cases where the events were closely observed. This speaks to the inherent uncertainty in rock-fall assessment. Prediction is still a goal but, as with earthquakes, we still have a long way to go.
It is possible to evaluate the stability of a rock mass by mapping the discontinuities (joints, faults, bedding planes, etc.) bounding that rock mass and making assumptions about the physical properties present. However, these sorts of analyses are better suited to small bedrock outcrops (e.g., roadcuts) than they are to the 1 kilometer-tall cliffs of Yosemite Valley. We have recently employed laser scanning (LiDAR) to map discontinuities, but have so far only scanned a small fraction of the 40 square kilometers or so of cliff area in the Valley. Another significant challenge is that many rock falls, including the recent one behind the Ahwahnee, fail along sheeting joints, or exfoliation joints, which parallel the cliff surface and are therefore not resolvable by remote sensing techniques. I am collaborating with the US Geological Survey this next year to instrument several flakes in the Valley to see if they move with daily and/or seasonal temperature fluctuations.
Regarding the apparent increase in rock fall activity in the past decade or so, I am not convinced that this is happening. As I posted in an earlier thread, the 1980’s had much larger and more consequential rock falls (in terms of injuries and fatalities) than this decade, but people are quick to forget. The database of historic rock falls does show more rock falls now than, say, 50 years ago, but that is almost certainly the result of increased reporting of rock falls, not an actual increase in the number of rock falls. Furthermore, 150 years of data may not accurately portray geological process rates. We are presently investigating the talus in Yosemite Valley to get a better perspective on this issue. The approach is to use GIS to isolate a talus pile in three-dimensions, calculate the talus volume (accounting for porosity), determine the contributing surface area of the adjacent cliff, and create a volume-frequency relationship for that location (the frequency part is possible by assuming that the talus accumulated since the last glacier retreated from the Valley about 17,000 years ago). So far we have done this analysis for Glacier Point, Royal Arches, Middle Brother, and Middle Cathedral. Overall we do not see that modern rates of talus accumulation are significantly larger than prehistoric rates, although Middle Brother is an exception because of the huge (600,000 cubic meter) rock fall on March 10, 1987, the largest historic event by far. We are still investigating this issue, but media statements that rock-fall activity has increased should be viewed skeptically.
Anyone wanting more information on this stuff is welcome to contact me. As always, I also appreciate hearing any information you may have about rock falls, possible precursor activities, etc.
Greg Stock
Yosemite Park Geologist
(209) 379-1420
greg_stock@nps.gov
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jstan
climber
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Aug 30, 2009 - 01:05pm PT
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Thanks Greg. Fascinating what all the new tools make possible.
If we would disarm all nuclear capabilities worldwide GPS precision could be opened up to the max. Don't know whether that can possibly give precision in the millimeter range.
Might add another argument for getting rid of that stuff.
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BMcC
Trad climber
Livermore
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Aug 30, 2009 - 05:28pm PT
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Photos?
Did this rockfall really come off the Royal Arches Route? (... and tumble over to the Ahwahnee Hotel?)
Seems like the RA route is a bit E of the Ahwahnee; although, part of the (valet?) parking extends E of the hotel.
Can Greg or someone tell us where on the cliff the rockfall originated? What did it hit on the way down and where did it land? What routes were affected?
Thanks. Be careful and lucky up and out there!
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cleo
Social climber
Berkeley, CA
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Aug 30, 2009 - 06:14pm PT
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fattrad, are you hoping they'll close the Ahwahnee and you'll get to move in as Emperor of Yosemite?
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gstock
climber
Yosemite Valley
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Aug 30, 2009 - 06:15pm PT
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The rock fall came from midway up the Rhombus Wall, directly behind the Ahwahnee and west of Royal Arches and Serenity/Sons. In the other rock fall thread Werner posted a photo that shows the source area. No popular climbs were affected, but please be aware that the approach to Serenity/Sons and Super Slide is within the rock-fall runout path. The approach to Royal Arches is east of the runout path, and the route itself is well clear of that.
Greg
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neebee
Social climber
calif/texas
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Aug 30, 2009 - 07:45pm PT
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hey there greg stock, say, this is very interesting, thanks so very much for taking the time to share all this with us...
love rocks... sad to see them fall on folks, though...
but,as we all know, rocks, do DO that...
good that folks can take to study it all...
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BMcC
Trad climber
Livermore
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Aug 30, 2009 - 08:52pm PT
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Greg -- thanks for the info and mention of the other thread (I had missed it). Just checked it out.
Werner -- thanks for the info and for the pointer on the photo.
Looks impressive on the MSNBC link.
Bill
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