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john hansen
climber
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Topic Author's Original Post - May 2, 2011 - 01:04am PT
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When did the rockfall from Elephant rock happen? That is a pretty big talus field. And did the Big rock on the riverside , by Cookie cliff come from the north or south side of the canyon. I am thinking the north side.
But where did the north side slide originate.
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WBraun
climber
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When did the rockfall from Elephant rock happen?
When the rocks fall then rockfall happens ......
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john hansen
climber
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Topic Author's Reply - May 2, 2011 - 01:27am PT
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It is true that at any given time in the valley you could have a rock fall kill you, You do not see boulder's in some places in the middle of the valley but I bet if you dug down you would find them in the silt along the river.
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Clint Cummins
Trad climber
SF Bay area, CA
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The USGS has a spreadsheet (1857-2003) of historical Yosemite rockfalls,
so you can look them up for pretty close or exact dates:
http://pubs.usgs.gov/of/2003/of03-491/of03-491.xls
It includes:
272 260R Elephant Rock-'Steamboat Bay' RS 12/??/1970 n/a 6000 very large ?
273 Elephant Rock-'Steamboat Bay' RS 3/4/1971 am 18000 very large UNR
319 304R Elephant Rock-'Steamboat Bay' RS winter, 1980-81 n/a 24000 very large P
More on this thread, including an updated map from Greg Stock:
http://www.supertopo.com/climbing/thread.php?topic_id=1469565&tn=0
The large boulders at the Cookie parking pullout came from NW - they blocked the road for awhile. Date: I believe it's this one:
326 311R old Coulterville Road-'Cookie' RS 4/3/1982 10:20 PM 100000 ext. large P
It's a good question about exactly where the 1982 Cookie rockslide originated. I've walked through it, and all around above it, and I'm not exactly sure.
Judging from the satellite photo above, there is no obvious path from the "Above the Cookie" crags to the highest white areas in the photo. This suggests there were some large blocks in the talus, or perhaps something next to the upper right end of the Cookie which gave way (perhaps wedged over by a tree) and rolled down the slope, knocking some other blocks loose. This does not match up with the "extremely large" volume from the rockfall list, though.
Since it has been 29 years, maybe something came off the wall up high (say just above the tunnel ventilation shaft) and came down without contacting much until it hit the talus. Vegetation knocked down could have partly grown back by now. I know when Eric and Ed did "the Drift" up there it was very loose. Photos from 1983-1988 or so would help shed light on this, and probably Werner and others know more.
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gstock
climber
Yosemite Valley
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As has already been posted, the huge scar on Elephant Rock was created by rockfalls in 1970 and 1971 (two events), with smaller rockfalls in August 2006. There are anecdotes about a great deal of river water - and perhaps even fish - splashed onto the road during the 1970's events.
On the opposite side of the river, the Cookie Cliff rockslide of 1982 originated from the top of the white path in Clint's photo above (similar photo from the top of Elephant Rock posted below). In those photos is doesn't look like there is any material to fail - that is because it all did! Basically, there were several large bedrock outcrops on the northeast edge of the Cookie Cliff that slid along an inclined joint plane (probably due to saturation of weathered bedrock along that plane). Those blocks then rolled and tumbled all the way to the river.
The huge white boulders between the road and river, and just uphill of the road, came from that event. The slide took out the El Portal Road, and damaged the sewer line under the road. It also buried the Old Coulterville Road (the old roadbed at the base of the Cookie Cliff), leading the Park Service to discontinue any maintenance of that road. The giant boulder just above the El Portal Road had to be extensively blasted in order to open up the road corridor again.
These rockfalls are discussed in detail in "Geology Underfoot in Yosemite National Park".
Greg Stock
Park Geologist
(209) 379-1420
greg_stock@nps.gov
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Tony Bird
climber
Northridge, CA
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i remember following the old dirt road to cookie cliff and the road disappearing under a garage-sized boulder. i imagine it's still there.
the story i heard--urban legend?--was that someone was doing a trad crack lead with hexes, up a good hundred feet when an earthquake happened. the jiggle loosened up all the pro, which came out of the crack and slid down the rope into the lap of the belayer, leaving the leader up there with nothing to hold a fall. anyone else hear that one? something werner cooked up? :-)
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Tork
climber
Yosemite
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Thanks Greg!
We need to get out and inspect some granite. Wawona Dome is looking dry!
Jeff
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Clint Cummins
Trad climber
SF Bay area, CA
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Thanks, Greg! I have wondered about this for awhile.
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Melissa
Gym climber
berkeley, ca
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I was sitting on the ledge on Enigma at the Cookie when the 8/06 slide happened. School bus sized block rolled end-over-end all the way to the edge of the water breaking off trees like broccoli. It was AWESOME.
Another time, maybe in 2004 or 2005, on a rainy winterish day (March?), we saw a good size fall from the vicinity of Trundling Juan from P&JP.
Cool shot of the Cookie slide!
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Kalimon
Social climber
Ridgway, CO
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Dec 10, 2018 - 07:15pm PT
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The place is falling apart.
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McHale's Navy
Trad climber
From Panorama City, CA
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Dec 11, 2018 - 03:00am PT
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I was in the middle of a rappel on the opposite side of the valley from Elephant Rock when the 1971 rockfall occurred. I can't remember what we where climbing but we were coming down because things were getting too wet. There was a low cloud ceiling but Elephant could still be seen. I heard a loud crack and thought it was lightning and turned around in my rappel in time to see the giant new ceiling on Elephant Rock, that we had talked about climbing earlier in the day, sailing through the air. It was pretty amazing and then the ozone drifted over us. After the boulders hit the river the water washed debris down from the opposite side of the road and closed the road.
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