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donini
Trad climber
Ouray, Colorado
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Topic Author's Original Post - Jan 26, 2014 - 09:50am PT
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ST geologists help me out here. The massive rockfall on Elephant Rock was not so long ago and I can remember driving to the base of the Cookie. It seems that every year a number of significant rockfalls occur, who now feels comfortable at the base of the Apron? Whats up...is this just normal geologic process or is something else going on?
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climbski2
Mountain climber
Anchorage AK, Reno NV
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Jan 26, 2014 - 10:09am PT
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I'm no geologist. Have not traveled as much as some but..
The only other place I have been with a similar amount of vertical rock in a comparable area is the Alaska range. Yosemite rockfall does not even come close to it. I would not be surprised if in a day I heard and saw as much rockfall as a person might in a year in Yosemite.
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donini
Trad climber
Ouray, Colorado
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Topic Author's Reply - Jan 26, 2014 - 10:11am PT
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Yes, but there is a lot of chossy rock in the Alaska Range and a lot of ice to lever rock off....not so in Yosemite.
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mooser
Trad climber
seattle
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Jan 26, 2014 - 10:18am PT
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I had the same thought, reading the "Apron Appreciation" thread, donini. I wouldn't spend a heck of a lot of time there, myself. That was the first place I ever climbed in the Valley, and generally one of the last places I feel comfortable at now.
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climbski2
Mountain climber
Anchorage AK, Reno NV
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Jan 26, 2014 - 10:22am PT
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I've always figured that some truly massive rockfall event in Yosemite is inevitable. Something big enough to completely cross the valley even. Gotta be a matter of time, Kinda like big earthquakes or asteroids and such.
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Brokedownclimber
Trad climber
Douglas, WY
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Jan 26, 2014 - 12:10pm PT
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Nobody in their right mind even goes near Lower Brother these days. BITD, that was a Camp 4 locals hangout.
I'm undecided about the Apron, but there are still several climbs there that I have on my "to do" list. Ditto, base of El Cap. Ditto, Church Bowl area.
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mongrel
Trad climber
Truckee, CA
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Jan 26, 2014 - 12:34pm PT
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Calling gstock.. calling gstock. Being the Park geologist, you know he is going to say, rockfall can happen any time blah blah. But the blah blah he has to contribute is always the most interesting imaginable commentary, about the triggers sometimes being ice or water, sometimes heat, big flakes flexing, there's been really interesting stuff about this in other threads (about the Hourglass, I think folks posted up about hexes squashed and the like).
The link above about recent rockfall is a really good paper. And you can download a huge spreadsheet of the details of every recorded rockfall.
If you want to convince yourself never to go to the Valley, do some surfing around and find a USGS map for which the citation is: G.F. Wieczorek, M.M. Morrissey, G. Iovine, and J.W. Godt. 1999. Rock-fall Potential in the Yosemite Valley, California. It's a huge wide map and I think it would blow up the format of the thread if I posted it. But if you can't find it, PM and I'll e-mail it. Basically, the entirety of all the valley slopes that aren't bedrock cliffs is rockfall or slide debris of some era. The issue is, how recent? So for this map, they outlined every deposit they could and colored it by "recent" "historic" or "prehistoric" and by what kind of debris. There's a lot of color! and some of those events were huge huge huge. About which Greg will say, this could happen any time.
But hey, aren't you a big fan of the Black Canyon? How stable is that stuff?
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mongrel
Trad climber
Truckee, CA
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Jan 26, 2014 - 12:39pm PT
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Here's that USGS map. If it ruins the thread I'll delete. Among other cool things you can see that (the former) Mirror Lake was formed by a rock slide that dammed the whole of the canyon. ROCK!
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Byran
climber
San Jose, CA
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Jan 26, 2014 - 12:44pm PT
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Lower Brother solid, it's the far left margin of Middle Brother (Koko Ledge area, just to the left of the Folly) that has all the rockfall. Elephant Rock is also one of the most bomber formations in Yosemite, it's just that obvious right side that has exfoliation issues and there's no reason to be over there. And the GP Apron acts as a natural barrier which diverts rockfall off to either side, so the more central climbs like Harry Daley, Goodrich, and the Grack are probably fairly safe. Common sense seems to keep the crowds away from the most active rockfall locations.
After a big cold storm, for the first couple days of sun I avoid the large steep formations and go climbing at the Cookie or somewhere small and solid. Really though the likelihood of being clobbered by spontaneous rockfall in Yosemite is extremely slim, most rockfall accidents are self-inflicted or caused by a party above. Compared to other climbing destinations of its size and caliber, the Valley probably has the least objective hazards to be found on earth.
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Spider Savage
Mountain climber
The shaggy fringe of Los Angeles
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Jan 26, 2014 - 02:53pm PT
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I am always very cautious. If you are standing on fresh talus, you are in an active zone. Although some of that could be from winter ice falls. Inside the great Royal Arch seems to get hammered pretty hard by that type of work. El Cap base too.
I'd rather not climb on The Apron, chased off by falling stones in the late 1980's.
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McHale's Navy
Trad climber
From Panorama City, CA
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Jan 26, 2014 - 03:27pm PT
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The massive rockfall on Elephant Rock was not so long ago
Jim, you mean the one in the early 70's? I was rappelling on the other side of the valley straight across from it, heard a crack like sharp thunder, turned around, and a huge ceiling was sailing through space. It hit the river and washed a wall of water over the hwy and closed the road.
There had been a huge slide earlier maybe that year that created the huge ceiling we were admiring just that morning. It's the one that came off for us. Must have been the size of a large house or so.
I was going up to Sickle Ledge once in the late 60s or early 70s and it had to be the the next morning after that big Magic Mushroom area collapse. The Nose up to Sickle was covered in dust, and every time the wind blew, it was in our eyes. We had no idea what was going on - nobody knew it had happened yet. Later that day we hiked around toward the Salathe and the forest and everything was obliterated. Soccer ball sized rocks came down for many months after that.
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donini
Trad climber
Ouray, Colorado
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Topic Author's Reply - Jan 26, 2014 - 10:42pm PT
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You got it Dan.
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Peter Haan
Trad climber
Santa Cruz, CA
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Jan 26, 2014 - 11:09pm PT
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Someone laminate up a copy of that Stzzo map asap for Jim. J-Do thought he was on solid ground all this time. You know, like on those things he used to do down under. I mean solid like a rock.
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bigbird
climber
WA
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Jan 26, 2014 - 11:11pm PT
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Always active rock fall= Troll Wall....
Its like the dark ugly cousin of the big wall world, that no one talks about....
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gstock
climber
Yosemite Valley
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Jan 27, 2014 - 02:27pm PT
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Well, it’s funny you should ask, as several of us geologist/climber geeks (Brian Collins, Lauren Austin, Roger Putnam, and I) just spent two days last week thinking hard about this issue.
To the opening question about whether Yosemite Valley is inordinately active, I think the answer is “no”. Exfoliation is an ongoing process in Yosemite and seems to be relatively steady over geologic timescales. We have a decent amount of data now to support that conclusion but it takes a bit of work to get there.
The database of historical rockfalls in Yosemite (http://pubs.usgs.gov/ds/746/ ) spans 155 years, from 1857 to 2011. If you simply plot the number of rockfalls per year, the obvious conclusion would be that rockfalls are increasing, with something like 5-6 times more rockfalls now than in the 1970’s for example. However, this conclusion would be flawed for the simple reason that the database depends almost entirely on reported rockfalls, and the rate of reporting has increased significantly through time. The earliest reports were either from local newspapers or the journal writings of people like John Muir and Joseph LeConte, but nowadays reports come in a variety forms (including postings on SuperTopo!) and from a much larger cadre of people. The plot of rockfalls by year below shows this bias in the “steps” that are associated with certain milestones the park’s level of rockfall documentation, e.g. the founding of the National Park Service in 1916, the involvement of the U.S. Geological Survey in rockfall studies beginning in 1980, and the hiring of Yosemite’s first park geologist (me) in 2006. I am assuming that the cliffs are not responding with a vengeance to these milestones! Bottom line – we cannot safely interpret any change in the number of rockfalls through time from the database.
However, a bright spot in the database is that rockfall volumes appear to be less affected by this bias. Plotted below are the largest rockfall volumes by year, from 1857 to 2011 (note the log scale in the y-axis). Ignoring the years when there are no data, you can see that there isn't an obvious trend of volume through time; i.e., there are not more large rockfalls now than there were a century ago. The annual variability in this plot may actually be similar to the real annual variability of large rockfalls. Without a doubt the small rockfall events have been – and still are – under-reported in the database, but because these small events make up such a tiny fraction of the total cumulative volume this doesn’t seem matter much.
So rockfall volumes appear to have been pretty consistent over the past 155 years, but as I’ve argued here before that isn’t a very long time from the geologic perspective. Can we do better? As it turns out, Yosemite Valley is a great place to derive long-term rates of rockfall activity because we know (1) the Valley was glaciated during the last ice age, (2) this glacier probably removed any previous talus, and (3) the Valley was free of ice by about 15,000 years ago, resetting the Valley floor. The talus that flanks virtually every major cliff in the Valley has accumulated in the past 15,000 years. Here is an example of what the Glacier Point Apron talus looks like in filtered lidar data:
We can measure the volume of the talus piles and divide by 15,000 years to come up with a long-term rate of rockfall activity (volume/year). When we compare these long-term rates with those derived from the historical database, they are basically in the same ball park, suggesting that rockfall activity has not appreciably changed through time.
This “steadiness” in rockfall rates through time makes sense to me because Yosemite is an exfoliating landscape. When a slab of rock falls away it reveals a new cliff surface, which progressively weathers and fractures and eventually fails again. Climate plays a role here, but ultimately the pace of exfoliation may be dictated by the properties of granite, which shouldn't change with time.
So those are my thoughts on whether the Valley is inordinately active now as opposed to back in the day. Next up – rockfall seasonality and triggering…
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gstock
climber
Yosemite Valley
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Jan 27, 2014 - 02:59pm PT
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One of the neat things about the Yosemite rockfall database is that it includes a lot of information about antecedent environmental conditions and probable triggers. We’re still analyzing this information in detail, but here are a few take-aways:
First, there isn’t really a pronounced “rockfall season” in Yosemite Valley. The plot below shows rockfalls by month from 1857 to 2011, and although there is some seasonality (there are more rockfalls in the spring and fewer in the summer), the difference isn’t huge. The fact that rockfalls occur pretty regularly at all times of the year suggest that there isn’t one dominant environmental trigger for rockfalls in Yosemite, as there might be in other settings.
We can also look at rockfalls by trigger. The first thing to note here is that more than half of all documented rockfalls either have “unknown” or “unrecognized” triggers. In the former case this means that there wasn’t enough information provided to evaluate triggering, and in the latter case it means that although the event was closely observed the usual triggers (precipitation, freeze-thaw, earthquakes, etc.) could be ruled out and another trigger wasn’t obvious. This is a particularly interesting subset of rockfalls, typified by those that occur on clear sunny days, and one we are actively investigating. If we ignore the unknown and unrecognized rockfalls, we’re left with the plot on the right, which shows the percentage of known and recognized rockfall triggers. Precipitation dominates here, which is good for climbers because we’re typically not out climbing during and immediately after rainstorms. The more subtle triggers that operate during good climbing weather probably pose a greater hazard – unfortunately those are the least understood of the triggering mechanims.
The NPS rockfall webpage is a good source of general information and includes links to just about everything that's ever been published about rockfalls in Yosemite: http://www.nps.gov/yose/naturescience/rockfal.htm
Greg Stock
Yosemite Park Geologist
(209) 379-1420
greg_stock@nps.gov
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stevep
Boulder climber
Salt Lake, UT
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Jan 27, 2014 - 03:14pm PT
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Very interesting Greg, though your rockfall by trigger graph appears to be missing the "Trundle by Climber" category.
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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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gstock
climber
Yosemite Valley
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C Wilmot, I'm not sure where you heard that I offered assurances that the Ahwiyah Point site was "safe", but that is not correct. To the contrary, I had concerns about the block you mentioned, and that is primarily why trail reconstruction didn't occur until three years after the rockfall. Despite what we might wish for, it just isn't possible to predict exactly when and where rockfalls will occur. It is for that reason that I, as a matter of practice, take a more nuanced approach than simply asserting that an area is “safe” (check out my posting history here for examples). I am relieved that nobody was in the vicinity when the block failed in October 2013.
In terms of the rockfall hazard and risk study (available here), the EOS article linked above provides justification for both the study and the resulting actions. Perhaps at some level it is obvious that boulders on the ground indicate rockfall hazard, but making good risk-based decisions requires thorough and quantitative science. “Common sense” is, unfortunately, subjective.
Feel free to call or email me if you’d like to discuss this more.
Greg Stock
Park Geologist
(209) 379-1420
greg_stock@nps.gov
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Captain...or Skully
climber
in the oil patch...Fricken Bakken, that's where
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Yer gonna die fer sure(still).....
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ß Î Ø T Ç H
Boulder climber
extraordinaire
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Concerning rockfall ... Oh, it's "concerning" all right.
That sinking feeling hearing the rattle of bones above you.
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Flip Flop
Trad climber
Truckee, CA
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Greg,
Is there any study of temperatures inside deep fissures in the Valley?
I noticed that rockfall rates rise in October when the temperature swings begin again. Freeze and thaw cycles are pretty impressive forces of nature.
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Reilly
Mountain climber
The Other Monrovia- CA
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It ain't a matter of if, to coin a phrase, is it? Seems to me that all of Curry
is sitting on borrowed time.
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gunsmoke
Mountain climber
Clackamas, Oregon
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Why is the lower canyon (west of Valley floor) active in the winter and the upper canyon relatively inactive in the winter? Could that be related to temperature triggers or other environmental factors, or just a statistical anomaly?
As noted by Greg, the majority of rockfall accidents to climbers are trigged by other climbers. Perhaps the Apron has become one of the safest places to climb. I've been in two rockfall accidents, both triggered by climbers not in my party.
And the map was used to make the decision to move some Curry Village cabins from locations which were fairly high risk.
Were they actually moved, or just removed as part of the unwritten policy to greatly reduce overnight accommodations in the Valley?
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rmuir
Social climber
From the Time Before the Rocks Cooled.
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did John Muir ever trundle?
Of course he did. Along with torching an entire tree in the Meadows just to have a rollickingly big bonfire one night, trundling is something of which he couldn't resist. He just couldn't admit it for fear of being tooled by the Man and getting booted from the Park. That Galen Clark was a real hard nose!
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Tom
Big Wall climber
San Luis Obispo CA
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All that fancy "science" aside, the real reason for the rapid exfoliation of the Valley walls is CAMMING UNITS.
A simple analysis will show that a climber's weight is multiplied, with the springy gadgets pushing out forcefully on flakes and buttresses, causing them to break off and fall.
Whatever happened to simply driving big angles to the tune of bing-bing-bing, or beng-beng-beng, or bong-bong-bong?
As I recall, there was no rockfall back then . . . . .
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Clint Cummins
Trad climber
SF Bay area, CA
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Cams = troll, given that you (should) know there were lots of rockfalls prior to the invention of cams.
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mouse from merced
Trad climber
The finger of fate, my friends, is fickle.
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I've told this before. I was with Millis when the first slide came off in the fall season when we were climbing Stigma--on pitons, very sketchily placed in the squeeziest of thin cracks.
If anything, the Valley is shaking because donini's coming back...
McHale's Navy, good to hear your tale. Loud sh!t, isn't it?
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Impaler
Social climber
Oakland
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Nov 10, 2014 - 01:29pm PT
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Just saw some cool rock fall in the Ribbon falls amphitheater on November 8. It wasn't that much rock, but the location amplified the sound a lot, so it sounded epic. The lower half of the amphitheater was filled with dust for about a minute. Rockfall originated about 1/2 way up the waterfall, which wasn't flowing at the time.
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rbord
Boulder climber
atlanta
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Nov 10, 2014 - 08:15pm PT
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I'm wondering what the other options for rockfall are other than normal geologic processes? Do we know what normal geologic processes are based on 200 years worth of data (or better yet, one lifetime of direct observation)? If we disprove every other hypothesis we can think of, will we have proven to ourselves that it's normal geologic process? I'd say that's a pretty normal human perspective :-) Can we say it's normal geologic process and admit that we don't understand exactly everything that means - every factor involved in every piece of rock falling? It's science dammit!
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Brock
Trad climber
RENO, NV
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Nov 11, 2014 - 07:12am PT
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I've climbed two routes just days prior to major rock fall. One was on The Great Book and the other was on Mr Natural. I remember fine granite dust being on the routes but no major sign of rock fall yet. Are there any warning signs being studied on potential rock fall sites?
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Reilly
Mountain climber
The Other Monrovia- CA
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Nov 11, 2014 - 07:17am PT
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I've been fortunate to have survived two extremely close rockfalls in the Valley but Mother
Nature had nothing to do with either unless she also influences klutzes.
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JEleazarian
Trad climber
Fresno CA
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Nov 11, 2014 - 12:07pm PT
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The first climbing books I read in the mid-1960's said to regard fine dust on the talus as a sure sign of recent, rather than future rockfall. Of course, they also implied that areas of recent rockfall would likely be areas of future rockfall, too.
The Apron seemed particularly immune from natural rockfall, so the events of the 1990's surprised me greatly. About all I can conclude after many decades in the Valley is that natural rockfall can happen anywhere there, and I'm unable to predict where or when with any degree of certainty.
Klutz-generated rockfall, on the other hand, is all-too-easy to predict!
John
Edit: Not only Muir, but Joseph LeConte, James Hutchinson, et al. documented trundling down the U-Notch. Since Greg's chart shows significantly less rockfall in the 1800's and early 1900's than now (Bias? What bias?), it naturally follows that trundling must have relieved pent-up pressure that resulted in more serious rockfall later. Thus, our inhibitionas on trundling now are clearly wrong-headed.
;-)
John
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Oplopanax
Mountain climber
The Deep Woods
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Nov 11, 2014 - 02:05pm PT
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Ow, right in the penstock!
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donini
Trad climber
Ouray, Colorado
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Topic Author's Reply - Nov 11, 2014 - 02:11pm PT
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Future behavior is most reliably predicted by past behavior, whether it be aminate or inanimate.
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rbord
Boulder climber
atlanta
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Nov 11, 2014 - 02:22pm PT
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Isn't that how our human brains work? Aren't all human predictions based on past observations? What else is there? What's the ratio of correct human predictions versus incorrect predictions?
For me, to think of it as normal geologic processes versus what? is just humans believing that we know the truth - that our current predictions are right. Sure, maybe. For me, the what? is not "abnormal" geologic processes, it's us admitting that we don't really know everything about what "normal" geologic processes are, but accepting that the reasons are normal even though we don't understand them. Sure lets keep trying to understand them :-)
Thanks for the thread!
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Studly
Trad climber
WA
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Nov 11, 2014 - 04:12pm PT
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Whoa, Throwpie, that's an amazing video! Exfoiliation in action, scary, I would have been running.
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