Yosemite rockfall database (1857-2011) published


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Yosemite Valley
Topic Author's Original Post - Jun 17, 2013 - 10:57am PT
Hi all,

I'm pleased to announce that, after several years of effort, an updated version of Yosemite's rockfall database has been published as a USGS Data Series Report.

The database, as well as an accompanying report and event narratives document can be downloaded here: http://pubs.usgs.gov/ds/746/

The database documents all known rockfalls, rockslides, and debris flows in Yosemite National Park from 1857 to 2011, a total of 925 events. Each entry includes information about event timing, location, size, potential triggering mechanism, and any human or infrastructure impacts. This information provides historical context for ongoing rockfall activity. An associated document provides narrative descriptions of the events, many of which are fascinating to read (at least for me). Here is but one example:

Credit: gstock

The database contains hundreds of eyewitness accounts from park visitors, employees, and residents, as well as information from internal reports and scientific journal publications. Climbers were an invaluable source of information for the database, so thank you for your reports, and keep them coming!

Thanks also to Luke Lydiard for providing the spectacular cover photo, taken from Middle Cathedral Rock.

As always, feel free to contact me if you have any questions.

Greg Stock
Yosemite Park Geologist
(209) 379-1420

Yosemite Valley
Topic Author's Reply - Jun 17, 2013 - 11:03am PT
Here's another entertaining narrative:

Credit: gstock
Credit: gstock
Clint Cummins

Trad climber
SF Bay area, CA
Jun 17, 2013 - 11:46am PT
haha, great line from Dick Ewert!
It's cool to see that you were able to find and interview eyewitnesses to some of these rockfalls in the past.
Thanks for putting together these interesting data and sharing the stories, too.

Trad climber
Nothing creative to say
Jun 17, 2013 - 12:34pm PT
Correction, found it!

"According to Park Geologist Greg Stock: A medium-sized rock fall occurred from the west face of El Capitan above El Capitan Gully, reported by numerous climbers and visitors who witnessed the event from El Capitan Meadow. A sizable dust cloud was produced as debris fell down the upper, lower-angle part of the west face. The source area was near the lip of the west face, northwest of climbing route "Lurking Fear" and southeast of KP Pinnacle. All of the debris stayed within El Capitan gully. Snowmelt was a possible trigger."


Trad climber
Fresno CA
Jun 17, 2013 - 01:06pm PT
Excellent. Thanks for all you do, Greg.

Dr. Christ

Mountain climber
State of Mine
Jun 17, 2013 - 01:12pm PT
Love it!
Doug Robinson

Trad climber
Santa Cruz
Jun 17, 2013 - 02:53pm PT
Thank you Greg!

This is a spectacular depth of information.

I immediately looked up the 1872 quake (Lone Pine) which killed some 27 people sleeping there in adobe shacks that night and apparently raised Mt. Whitney twenty feet at once -- a year before it's First Ascent.

For years I had been looking for information about the toppling of "Eagle Rock" in the Valley, even asking at the great research library there, and finding very little.

You did it! You came through with the information. Exactly what I needed, including quotes from Muir. Now I finally know where Eagle Rock was, off of Union Point. And of the other massive rockfalls that night from Sentinel, Liberty Cap and the also no-longer-with-us "Pelican Peak."

This is great because it fleshes out events showing the huge quake's magnitude (greater than the famous San Francisco quake of 1906) from these rockfalls over a hundred air miles away from the epicenter.

I'm really excited here because I'm writing about this massive Sierra event for a major piece in the American Alpine Journal for next year, and you have given me the best, most colorful and accurate info yet found.

Thank you. Thank you!


Trad climber
the middle of CA
Jun 17, 2013 - 05:37pm PT
bump. Cool

Yosemite Valley
Topic Author's Reply - Jun 17, 2013 - 06:27pm PT
You're welcome Doug! Actually, I should be thanking you for your enthusiasm - I'm happy to know that all of that work is worth something to somebody!

Given your interest in the 1872 earthquake and its effects in the Sierra, you'll probably also find this article interesting:



Jun 17, 2013 - 06:54pm PT
(This rock) [It] was 1500-ft-high + (was) capped by a large stone somewhat like an eagle with wings outspread
Any hope of finding a photo (or drawing) when it still stood?

Trad climber
Jun 17, 2013 - 07:05pm PT
very cool

say, the mapping project we just got a link to mentions very large rockfall from el cap that occured several hundred years back

any more details available about that event?

Yosemite Valley
Topic Author's Reply - Jun 17, 2013 - 08:02pm PT
Regarding the El Capitan rock avalanche circa 3,600 years ago:

Easy-reading version here: http://www.supertopo.com/topos/yosemite/El-Capitan-avalanche.pdf

Technical article here: http://www.nps.gov/yose/naturescience/upload/rock-fall-el-cap-stock-uhrhammer.pdf

Trad climber
Jun 17, 2013 - 11:51pm PT
thanks g!

good reads.
this begs two questions now. three actually

was el cap completely buried by ice in the last ice age?
id always thought of the valleys shape being the work of several encroachments of varied degree of severity

the oldest rocks theyve tested seem to show exposure long before the ice settled in the last time... am i miss reading that?

whats the oldest date or rock samples from the summit presently?

Trad climber
Jun 18, 2013 - 12:35am PT
Greg, Thank you so much for your hard work! This is an invaluable source of information.

Trad climber
The great state of advaita
Jun 18, 2013 - 01:09am PT
Wow, very interesting and enjoyable tales here! Thanks Greg!

I'm looking forward to Doug's article too.

Peter Haan

Trad climber
Santa Cruz, CA
Jun 18, 2013 - 08:15am PT
rSin, excellent info for you here: http://www.yosemite.ca.us/library/geology_of_yosemite_valley/

The last stage of glaciation reached only top 1/3 the height of El Cap and barely passed its toe as well. When you are up high on El Cap, it becomes really obvious that the upper reaches did not get planed off like the lower parts and must have been untouched for quite a bit longer.

Mountain climber
The Other Monrovia- CA
Jun 18, 2013 - 09:07am PT
Peter, are you saying the glaciar was 1000' thick and had a 1000' terminal face
like a tidewater glaciar?

Yosemite Valley
Topic Author's Reply - Jun 18, 2013 - 09:26am PT
The last major glaciation in Yosemite, known locally as the "Tioga" glaciation, terminated just west of Bridalveil Fall and covered only the lowest part of El Capitan (about 4% of the face). You can see still see some glacier polish on the first pitch of Mescalito/New Dawn, and on the ledge at the base of Pine Line.

Earlier glaciations were larger, extending as far downvalley as El Portal and covering most or all of El Capitan.

In this recent revision of the Yosemite glaciation series, the far left panel represents Yosemite Valley as it might have looked several million years ago before glaciation; the middle left panel shows the largest glaciation perhaps about 800,000 years ago; the middle panel shows the Tioga glaciation about 20,000 years ago; the middle right panel shows the Valley after deglaciation about 15,000 years ago; and the far right panel shows Yosemite Valley today.

Yosemite Valley glaciation series
Yosemite Valley glaciation series
Credit: Illustration by Eric Knight, courtesy NPS
Don Mellor

Jun 18, 2013 - 11:13am PT
I saw that one happen on El Cap from Middle Cathedral. It would have been mid/late October 1976. It was huge. A few days later as we walked to E Butt, the dust was like snow on the ground. We ran through it, leaving footprints in the powder.
Don Paul

Big Wall climber
Colombia, South America
Jun 18, 2013 - 01:37pm PT
Greg, what's your take on whether it makes sense to make a list of loose blocks on popular routes, then close the routes for a day and trundle them? Is this a "sisyphian task" - ie, it never ends and more death flakes will just be produced, or could the routes be cleaned up? If it makes no sense, because flakes are coming off all the time, then so be it. Note the recent post about a death flake on the Nose. I remember a different death flake, way up around the glowering spot I think, that's no longer there. But maybe there is no end to it.
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