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Gene
Social climber
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Greg,
Bogus link.
g
EDIT: Works now!
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Clint Cummins
Trad climber
SF Bay area, CA
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Cool article, Greg - congrats on the publication.
Here is the abstract which gets straight to it, and a key photo/diagram:
White dashed area is computed likely source area for huge rockfall, at around 1600 BC (3.6 ka ago).
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 × 10^6 m^3 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 ×
10^4 m^2. 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.
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tinker b
climber
the commonwealth
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i can't get the link to work, but thanks for everything else greg.
j-l
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Dr.Sprock
Boulder climber
Sprocketville
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are there any park rules that say you can not climb during a major earthquake?
because that would be all we need, more regulations,
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HighTraverse
Trad climber
Bay Area
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Sprock
You're specifically exempted from that regulation.
"Subpart B, Clause 9: Dr. Sprock, owing to his well documented anti-authoritarian nature is exempted from all other sections of this regulation. However, even for Dr. Sprock, the Laws of Nature will not be exempted not excluding the law that being crushed by a 5700 ton boulder will lead to instant death"
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HighTraverse
Trad climber
Bay Area
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I had wondered about that big fan of talus spreading out below ElCap. It sure seems a long way for a boulder to travel on its own.
Wonderful research Greg. Chris, thanks for posting.
It will be really interesting to follow this work through the years.
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Wade Icey
Trad climber
www.alohashirtrescue.com
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CalicoJack
climber
CA
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Big wall field work w/ big rock fall forensics - FANTASTIC!!!
Very cool work!
Cheers,
Andy
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Gunkie
Trad climber
East Coast US
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In other words, there are lots of boulder problems that need unearthing.
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FRUMY
Trad climber
SHERMAN OAKS,CA
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TFPU
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SuperTopo on the Web
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Let us know!