Massive rockfall - Waterfall route

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10b4me

Mountain climber
Retired
Sep 30, 2017 - 01:45pm PT
What's interesting about Werner's graph is that those are ambient temps. It has been my experience in taking surface temp readings that those ranges are even greater on the surface of an object.

yes, take the air temp six feet above astreet, then take temp six inches above street.
Reilly

Mountain climber
The Other Monrovia- CA
Sep 30, 2017 - 01:58pm PT
And then take it 2 meters inside the rock. Don't think yer gonna see much of a swing in the course of a day, or even a week.
WTF

climber
Sep 30, 2017 - 02:28pm PT
Perhaps not. I suspect after one of the hottest summers on record and the drastic cooling we had a week or so ago then a rapid return to the high 90's would that contraction and then rapid expansion of surface materials be part of the equation.

It would be interesting to me to go back to those events over the time of record and cross reference the high and low temps and see if a correlation existed.

Perhaps a waste of time given the medium but could be a potential for warning if there were some correlation in temps and when the event took place.
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Sep 30, 2017 - 03:03pm PT
Finally, our results offer a potential explanation for rockfalls that have no recognized trigger despite sometimes detailed observation at the time of failure. These include records of spontaneous summertime rockfalls in Japan, France, Brazil, Switzerland and Yosemite. In Yosemite, a disproportionate number (15%) of rockfalls with either an identified thermal stress trigger or an unrecognized trigger occur during the hottest summer months (July through September) and at the hottest times of the day (12:00 through 18:00 PST) compared to what would be expected under a random distribution (6%). We suggest that cyclic thermal stresses might be the trigger for these rockfalls and potentially many others around the world, highlighting the role of temperature in eroding steep landscapes.

Rockfall triggering by cyclic thermal stressing of exfoliation fractures
Brian D. Collins & Greg M. Stock.
The manuscript was submitted in Sept 2015.
WTF

climber
Sep 30, 2017 - 03:33pm PT
Tradster

Thanks for the post. It just makes sense to me that this could be a trigger. A product we used in the industry I was in was know to contract and expand 130% of its natural state on a surface. The polymers were designed to do this based on surface temperature variations throughout the day on those surfaces.

These products had a surface life on average of 10 years. They typically began to fail when an imperfection in either the surface or substrate was present. As we know there are plenty of imperfections in the rock. A combination of freeze thaw and a line of weakness will result in a crack and eventual failure. Imagine how many times the water on the waterfall has filled the seams and cracks and then froze where this took place. Combine that natural system with the expansion of a hot summer and then a cooling and it's probably a given it will fail at some point.

It will be interesting to watch the recent fall area over the next few years as I'm sure it will have opened up new areas for water travel and the repeated cycle of freeze thaw and expansion.

Anyway again thanks for the post.
zBrown

Ice climber
Sep 30, 2017 - 04:18pm PT
Good sleuthing around t_t.

Don Paul

Big Wall climber
Denver CO
Sep 30, 2017 - 04:22pm PT
In materials science, failures are often attributed to crack propagation. Granite is a common building material - an internet search turned up lots of studies in fields other than geology. For example, Thermal and Moisture Expansion Studies of Some Domestic Granites

The different minerals in granite have different linear expansion coefficients, which are anisotropic (depends on which direction in the crystal), not to mention ice, which is five times higher. It also apparently undergoes a ductile brittle transition at high strain rates. I haven't worked in this field in many years but my bet is on the thermal cycling and not Pete's junk show, whatever that is.
High Fructose Corn Spirit

Gym climber
Sep 30, 2017 - 04:33pm PT
Has anyone posted a trace here or elsewhere of the principle route or routes that used to go through the area? That would be so informative and interesting to see. (Not just the routes or trails hit by the rockfall but the route or routes that used to go through the affected area.)
Gene

climber
Sep 30, 2017 - 04:43pm PT
Taken from Nanook's book under fair use doctrine
Taken from Nanook's book under fair use doctrine
Credit: Gene
High Fructose Corn Spirit

Gym climber
Sep 30, 2017 - 04:46pm PT
Gene, thanks!
ec

climber
ca
Sep 30, 2017 - 05:18pm PT
#17 is in several spots that don’t make sense
aspendougy

Trad climber
Los Angeles, CA
Sep 30, 2017 - 05:21pm PT
I just read that the man who died saved his wife's life by jumping on top of her and shielding her. My heart goes to the family and friends of this brave soul.

I am wondering about how much piton pounding still goes on with these El Cap routes. Most everyone is doing most everything clean, but evidently not all?

FROM MSN:

LONDON — A British newspaper is reporting that the Welsh climber killed by falling rock in Yosemite National Park this week died while trying to shield his wife.

The Times says Andrew Foster's wife, Lucy, told her husband's aunt that he jumped to cover her as tons of rock came cascading on Wednesday down the face of El Capitan, a 3,600-foot granite monolith that attracts climbers from around the world.

Gillian Stephens, in an interview with the Times published on Saturday, says Lucy Foster told her: "Andrew saved my life. He dived on top of me as soon as he could see what was going to happen. He saved my life."

The couple, who lived in Cardiff, Wales, described their love of the outdoors in a blog, Cam and Bear.
ec

climber
ca
Sep 30, 2017 - 05:47pm PT
I am wondering about how much piton pounding still goes on with these El Cap routes. Most everyone is doing most everything clean, but evidently not all?

Lots...some passages cannot be negotiated with ‘clean’ gear...

 ec
klaus

Big Wall climber
Florence & Normandy
Sep 30, 2017 - 07:01pm PT
ec, there are several errors on Sloan's lines in that pic. Weird that he made so many mistakes but hey it is Sloan after all.
moosedrool

climber
Andrzej Citkowicz far away from Poland
Sep 30, 2017 - 08:37pm PT
I saw PTPP today. Judging by his IQ, he is alive by pure luck.

Sorry Anita.

Moose
tuolumne_tradster

Trad climber
Leading Edge of North American Plate
Sep 30, 2017 - 09:14pm PT
Check out the description below of the rock avalanche event ~ 3,600 years ago in El Cap Meadow (black).
>1.64M m^3 of granite...100 times more granite than the 9/29/17 event.




Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California

June 2010 
DOI: 10.1002/esp.1982

Greg M Stock and Robert A Uhrhammer
Abstract
Large rock slope failures from near-vertical cliffs are an important geomorphic process driving the evolution of mountainous landscapes, particularly glacially steepened cliffs. The morphology and age of a 2·19 × 106 m3 rock avalanche deposit beneath El Capitan in Yosemite Valley indicates a massive prehistoric failure of a large expanse of the southeast face. Geologic mapping of the deposit and the cliff face constrains the rock avalanche source to an area near the summit of ∼8·5 × 104 m2. The rock mass free fell ∼650 m, reaching a maximum velocity of 100 m s−1, impacted the talus slope and spread across the valley floor, extending 670 m from the base of the cliff. Cosmogenic beryllium-10 exposure ages from boulders in the deposit yield a mean age of 3·6 ± 0·2 ka. The ∼13 kyr time lag between deglaciation and failure suggests that the rock avalanche did not occur as a direct result of glacial debuttressing. The ∼3·6 ka age for the rock avalanche does coincide with estimated late Holocene rupture of the Owens Valley fault and/or White Mountain fault between 3·3 and 3·8 ka. The coincidence of ages, combined with the fact that the most recent (AD 1872) Owens Valley fault rupture triggered numerous large rock falls in Yosemite Valley, suggest that a large magnitude earthquake (≥M7.0) centered in the south-eastern Sierra Nevada may have triggered the rock avalanche. If correct, the extreme hazard posed by rock avalanches in Yosemite Valley remains present and depends on local earthquake recurrence intervals. Published in 2010 by John Wiley & Sons, Ltd.

Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California. Available from: https://www.researchgate.net/publication/227781417_Catastrophic_rock_avalanche_3600_years_BP_from_El_Capitan_Yosemite_Valley_California [accessed Sep 30, 2017].
Cosmiccragsman

Trad climber
AKA Dwain, from Apple Valley, Ca. and Vegas!
Sep 30, 2017 - 09:21pm PT
I saw PTPP today. Judging by his IQ, he is alive by pure luck.




The only reason Moose is in Yosemite right now...

No wonder Moose is, DROOLING.
No wonder Moose is, DROOLING.
Credit: Cosmiccragsman
clinker

Trad climber
Santa Cruz, California
Sep 30, 2017 - 09:38pm PT
How far is Middle Cathedral from El Capitan?
rottingjohnny

Sport climber
Sands Motel , Las Vegas
Sep 30, 2017 - 09:42pm PT
Cosmogenic...No wonder your back is messed up....
Jim Brennan

Trad climber
Sep 30, 2017 - 09:47pm PT
The recreational climbers like "Moose" can never even begin to really understand the difference.
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