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Aerili
climber
SLC, Utah
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Jan 27, 2014 - 03:14pm PT
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The days I spent in the French Alps this past summer I heard spontaneous rockfall every single day/night I was out there (and visually witnessed one on a nearby wall while on a route).
While I was almost killed by spontaneous rockfall on the Apron in 2011, I have never otherwise heard/seen daily rockfall in the Valley like that in the Alps. So I would agree that it is probably not inordinately active.
P.S. I have also climbed on Lower Brother and base of El Cap without a helmet and never worried for a second about rockfall. . .
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Plaidman
Trad climber
South Slope of Mt. Tabor, Portland, Oregon, USA
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Jan 27, 2014 - 03:16pm PT
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Thx Greg. Great info. Lots of hard work there. Thx for keeping us informed.
Plaid
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gstock
climber
Yosemite Valley
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Jan 27, 2014 - 03:18pm PT
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Yes, I should note that I specifically excluded climber-induced rockfalls from the database. Those events don't tell us much about natural triggering of rockfalls but they do represent the majority of climber injuries and fatalities in Yosemite.
Yosemite Valley has more documented rockfalls than any comparably sized area, but again the key here is that the events are documented. I have no doubt that areas in the Alps, Himalayas, Alaska, etc. experience larger and more frequent rockfalls but they are not as well documented so we cannot make meaningful comparisons.
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Aerili
climber
SLC, Utah
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Jan 27, 2014 - 03:25pm PT
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^^^ Right, gstock. Clearly my experience is purely anecdotal and limited. :)
Sincerely,
The daughter of a geologist
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mcreel
climber
Barcelona
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Jan 27, 2014 - 03:39pm PT
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That filtered photo of GPA is really interesting. Thanks for that and the other interesting information.
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Vitaliy M.
Mountain climber
San Francisco
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Jan 27, 2014 - 03:59pm PT
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Is it just me, or does the North Face of Middle Cathedral has more frequent large rockfalls than other areas? Love that place, but I think I have seen rock fall twice there and saw the video about it while M. Schaeferer (pretty sure messed up the last name, sorry) was working on "Father Time."
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Clint Cummins
Trad climber
SF Bay area, CA
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Jan 27, 2014 - 04:34pm PT
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Vitaliy,
There have been several there on the North Apron of Middle Cathedral, as seen in the map above (above "th" in Cathedral).
Whether there are more or less than other cliffs depends on which cliff.
And there are many ways to normalize a rate of "large enough" rockfalls.
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JEleazarian
Trad climber
Fresno CA
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Jan 27, 2014 - 04:58pm PT
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When I first started climbing in the Valley in the late 1960's, we considered the Apron one of the most resistant areas to rockfall. The southeast face of the Three Brothers, in contrast, we considered the least stable, and the northwest face of Half Dome was another one that I thought was particularly active. I think history has confirmed the danger on the southeast face of the Brothers (particularly that of Middle), but I've learned the hard way that almost every cliff has some significant instability.
It was good to get Greg's reminder that the exfoliation process continues constantly. There may not be that much I can do about it, but at least it motivates me to wear a helmet once in a while.
The rockfall I'm most curious about, though, is one that's about 150 years old, when a large earthquake caused one of the (then) three Cathedral Spires to fall. Does anyone have any information about what the missing spire looked like? Was it perched on top of the Church Tower? That seems most likely to me, but the nature of the rock, particularly on Church Tower and Lower Spire, always made me nervous about further destruction in an earthquake.
Anyone know anything about this?
Thanks.
John
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gstock
climber
Yosemite Valley
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Jan 27, 2014 - 07:21pm PT
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Sorry Aerili, I didn't mean to come across as dismissive - I was actually trying to agree with you in my nerdy scientist way.
Middle Cathedral has had several notable rockfalls since about 2000, and there are a few threads here about them:
http://www.supertopo.com/climbers-forum/1552021/Yosemite-Middle-Cathedral-huge-rockfall-July-12
http://www.supertopo.com/climbers-forum/2095755/Middle-Cathedral-Rock-Fall-3-16-2013
http://www.supertopo.com/climbing/thread.php?topic_id=1784752&tn=0
When we did the talus volume calculations and normalized them by contributing cliff area (to be able to compare with other cliffs), Middle Cathedral and El Cap came out on top in terms of having the greatest amount of long-term rockfall. Royal Arches and, surprisingly, Glacier Point, came out on the bottom. So that analysis at least would suggest that Middle Cathedral is more rockfall-prone than some other cliffs.
John, I have heard rumors of the collapse of the "third" Cathedral Spire for awhile now, but I haven't found anything published that specifically refers to it. The most closely related anecdote that I know of is this 1868 account by Josiah Whitney (head of the California Geological Survey and for whom Mount Whitney is named):
"We see that fragments of rock are loosened by rain, frost, gravity, and other natural causes, along the walls, and probably not a winter elapses that some great mass of detritus does not come thundering down from above, adding, as it is easy to see from actual inspection of those slides which have occurred within the past few years, no inconsiderable amount to the talus. Several of these great rock-avalanches have taken place since the Valley was inhabited. One which fell near Cathedral Rock is said to have shaken the Valley like an earthquake."
Although I haven't been on Church Tower yet, I can easily convince myself that there was once a larger spire there.
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kaholatingtong
Trad climber
Nevada City
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Jan 27, 2014 - 11:08pm PT
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greg, you the man. thanks again for sharing with us in such great detail.
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thebravecowboy
Social climber
Colorado Plateau
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Jan 27, 2014 - 11:11pm PT
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thank you for sharing, gstock.
my gut told me "no."
fact: you have more nerves in your gut than in your brain.
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Dr.Sprock
Boulder climber
I'm James Brown, Bi-atch!
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Jan 28, 2014 - 12:03am PT
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what about trundle rates?
did John Muir ever trundle?
Mark Twain?
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Aerili
climber
SLC, Utah
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Jan 28, 2014 - 12:23am PT
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Sorry Aerili, I didn't mean to come across as dismissive - I was actually trying to agree with you in my nerdy scientist way.
Oh no, I totally agree with you that meaningful comparisons can't be made without similar records. I just didn't think about that before I made my dumb, qualitative comment. :)
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paul roehl
Boulder climber
california
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Jan 28, 2014 - 01:47am PT
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Rockfall in the Valley is statistically irrelevant until you’re looking up at it.
I don’t know why those kinds of changes are so depressing… I remember that flake at the base of Yosemite falls when it came off, It just seemed so sad or when Werner’s crack came down it seemed to violate some kind of expected permanence that is, I suppose, illusory.
Maybe what’s needed is some more nuclear testing in Nevada to clean away the debris and potential debris in the Sierra or another great earthquake… I just wish there was something that was really permanent. The Valley seduces you with a sense of permanence, and yet…
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phile
Trad climber
SF, CA
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Feb 10, 2014 - 02:21pm PT
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Fascinating stuff--thank you.
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RP3
Big Wall climber
Twain Harte
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Actually, the knowledge of Yosemite rockfall mechanics, recurrence intervals, and hazard areas has grown by orders of magnitude over the past several decades. I'm not sure how much you were paying attention during Greg's talk...
Also despite all this research they still have no way of predicting danger zones, or have any idea on what might fall. So what was the point of spending all that money on this research?
Just because we don't have an answer yet to a scientific question should we stop researching it? Especially research on a topic with significant safety implications such as rockfall? That seems pretty stupid to me. Let's stop researching other unanswered questions such as how to predict earthquakes or a cure for ebola. Since we haven't found answers to these questions yet, f*#k it...
-Roger Putnam
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Clint Cummins
Trad climber
SF Bay area, CA
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despite all this research they still have no way of predicting danger zones Not true. The research yielded a map which showed frequency of rockfall.
And the map was used to make the decision to move some Curry Village cabins
from locations which were fairly high risk.
Like Roger said, we can't predict the future perfectly,
but getting an estimate of the level of risk is helpful for decisions.
That sucks about your worksite under Ahwiyah Point, though.
[Edit to add:] It sounds like it was a misunderstanding.
I agree with what Greg posted below -
I think he would be the last person to say a location is "100% safe".
95% safe, maybe. But sometimes or eventually the 5% will happen.
Good thing it didn't happen when you were there.
It can be pretty jarring when you go to a place where you have spent time,
and it has been demolished by rockfall.
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RP3
Big Wall climber
Twain Harte
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The research yielded a map which showed frequency of rockfall.
And the map was used to make the decision to move some Curry Village cabinsfrom locations which were fairly high risk.
In fact, there was a rockfall above Curry Village last winter that dropped a whole bunch of debris right in the area where those cabins used to be. Property and possibly lives were saved as a result of this work. Greg and Brian Collins wrote a short article about it for EOS. Check it out here
Amen about the worksite. The science is not perfect yet. However, this is is precisely why we must continue to refine it rather than disregard the whole field. It sure is a lot better than it was a decade ago!
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