Middle Cathedral Rock-Fall 3/16/2013!

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Vitaliy M.

Mountain climber
San Francisco
Topic Author's Original Post - Mar 18, 2013 - 07:30pm PT
Did anyone else see it? Knows anything about it?

Happened mid day. Just left of the water streaks which split the formation in half. Was very loud and had a lot of stuff coming down. I got my camera out just after majority of it passed..

Rock Fall Middle Cathedral 3.16.13 &#40;smoke left of middle water streak&#41;
Rock Fall Middle Cathedral 3.16.13 (smoke left of middle water streak)
Credit: Vitaliy M.
pell

Trad climber
Sunnyvale
Mar 18, 2013 - 07:39pm PT
Rockfall on Middle Cathedral Rock. Sat Mar 16, 2013 around 10:45am
Rockfall on Middle Cathedral Rock. Sat Mar 16, 2013 around 10:45am
Credit: pell

We were approaching El Cap base. I did a couple shots.

Seems it was not too far from DNB.

It happened around 10:45am.
cleo

Social climber
the canyon below the Ditch!!!!
Mar 18, 2013 - 08:36pm PT
Make sure gstock gets a good report!
le_bruce

climber
Oakland, CA
Mar 18, 2013 - 08:42pm PT
From 3 pitches up. Looked like it came down right over the North Buttress route. Loud for sure, but maybe not huge in terms of material released? Good reminder, in any case, of the many ways that we all spin the roulette wheel day in and day out in life.





donini

Trad climber
Ouray, Colorado
Mar 18, 2013 - 08:56pm PT
Vitaliy....shore those cliffs up, i want some climbing left when i get there in May.
GDavis

Social climber
SOL CAL
Mar 18, 2013 - 09:36pm PT
quick, check the base for new bad ass talus bouldering!!!!! If it is so good in RMNP there has to be some awesome blocks sitting at the base waiting for your radness***, and probably still warm, too!
Cosmiccragsman

Trad climber
AKA Dwain, from Apple Valley, Ca. and Vegas!
Mar 18, 2013 - 09:49pm PT
Been TRUNDELING up there in Yosemite again, EH, Vitaliy?
Clint Cummins

Trad climber
SF Bay area, CA
Mar 19, 2013 - 07:49pm PT
Yes, it looks like it came down the North Buttress.
Adamame

climber
Santa Cruz
Mar 19, 2013 - 07:51pm PT
Looks pretty small compared to some of the rockfalls in that are from past years. Good thing there are raptor closures over there right now.
survival

Big Wall climber
Terrapin Station
Mar 19, 2013 - 09:21pm PT
Good thing I wuz waring muh helmet and muh shouldamuhpads. Oh, and my cup.
Fat Dad

Trad climber
Los Angeles, CA
Mar 19, 2013 - 09:24pm PT
Some 30 yrs. ago, I was on the East Butt. of MCR and some rockfall came down the Spires gully. The volume and cacaphony was just crazy. Still very vivid all these years later.
TomCochrane

Trad climber
Santa Cruz Mountains and Monterey Bay
Mar 19, 2013 - 09:34pm PT
the biggest rockfall i've ever experienced seemed like a few of tons of boulders crashing around past us while sitting on top of Dolt Tower in 1985
limpingcrab

Trad climber
the middle of CA
Mar 19, 2013 - 09:54pm PT
Who's gonna get the FA of that new tan spot!?!
lucander

Trad climber
Shawangunks, New York
Mar 19, 2013 - 10:49pm PT
I heard that the guy who has been chipping in the Gunks has been in California.
Sierra Ledge Rat

Mountain climber
Old and Broken Down in Appalachia
Mar 19, 2013 - 11:51pm PT
Yes, it looks like it came down the North Buttress.

1+

Looks like a direct hit
Wonder how the route changed
Walleye

climber
The Hot Kiss on the end of a Wet Fist
Mar 20, 2013 - 08:49am PT
Middle Rock, still the best bowling alley west of the Mississippi!
gstock

climber
Yosemite Valley
Mar 20, 2013 - 12:30pm PT
Thanks for the report and great photos. There have been many rockfalls from Middle Cathedral in the past two years. Happily I've already ticked the North Buttress!

A couple of years ago we measured talus volumes beneath several of the major cliffs in the Valley, and then normalized the volumes by the size of the cliff above it. This allows us to directly compare long-term rockfall activity from the different cliffs over the past 15,000 years or so. The results, listed in terms of more rockfall to less rockfall are:

1. El Capitan (Salathe Wall)
2. Cathedral Rocks
3. Middle Brother
4. Glacier Point
5. Royal Arches

Interesting that Glacier Point, which has a reputation for rockfall, actually has had fewer rockfalls (or at least smaller rockfalls) over time than El Capitan. This highlights how much our individual experience colors our perception of hazard and risk. We evaluated this pattern with respect to many different variables and found the best correlation with degree of glaciation - basically, the cliffs that were extensively glaciated have had fewer rockfalls, most likely because the fractured, weathered rock in those areas was cleaned off by glacial erosion.

Greg Stock
Park Geologist
greg_stock@nps.gov
(209) 379-1420
Clint Cummins

Trad climber
SF Bay area, CA
Mar 20, 2013 - 12:37pm PT
I'm surprised about the result for the Salathe' Wall. Do you really mean El Cap Gully and face over to Ribbon Falls (left of the West Face of El Cap) as the source of the talus field? I am thinking the big slope under El Cap Gully / West Face / SW Face is different rock (e.g. KP Pinnacle) from El Cap itself (say West Face). I'm thinking this different granite mix type collapsed a long time ago. Vs. continually fell off of El Cap right until the present.

I'm not sure if that normalization for "rockfall activity rate" works so well for Glacier Point, because about half of its height is a very smooth slab that should not produce any major rockfall. The upper half, with the trees, etc. should be where the rockralls come from. And when they come down, they won't be slowed down much by barriers on the slab!

[Edit:] Thanks for the extended answers, Greg!

There are a few different rates which could be calculated, due to the dimensions like frequency over time, volume, etc.
For example, the huge rockfall event out of the NA Wall:
 huge on the volume scale
 maybe small on the frequency of time scale

I guess we climbers may perceive risk on the frequency over time scale, for volumes large enough to kill us.

Is there a way to use the size of unforested talus slopes as an indicator of active rockfall areas?

How would the huge unstable talus slope under Nuts Only Cliff figure on your activity rate scale?
gstock

climber
Yosemite Valley
Mar 20, 2013 - 12:54pm PT
Clint, our calculation was for just the talus underneath the Salathe Wall proper, exclusive of debris that came from KP Gully or from the Ribbon Falls area. It surprised me too, but look at the size of that talus pile!

West Face of El Capitan from Lower Cathedral
West Face of El Capitan from Lower Cathedral
Credit: gstock

One big unknown though is exactly where the bedrock is under the talus. We investigated this at Glacier Point with geophysics (seismic, resistivity, and ground-penetrating radar) and found that the talus there was sitting on river sediment. But we haven't done that at El Capitan, so it's possible that the volume is large because some of it is bedrock.

Regarding Glacier Point, you are correct that the Apron has had very few rockfalls (there is still glacial polish there). However, even when we exclude the lower portion of the cliff area below the glacial trimline, the adjusted rate is still somewhat lower than El Capitan.

The problem with the talus of the Rockslides area (Nuts Only Cliff) is that it was downvalley of the maximum extent of recent glaciation, so it has been accumulating for much longer.

Greg
Clint Cummins

Trad climber
SF Bay area, CA
Mar 20, 2013 - 01:04pm PT
It's cool that there are still many basic unknowns like the bedrock level under the slope below the SW Face of El Cap.
The slope still doesn't look like an "active rockfall slope" to me because of the trees. More like a "historic rockfall slope"?
Perhaps it's my bias to the time dimension here again.
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