Ahwiyah Point rockfall

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Messages 1 - 120 of total 120 in this topic
gstock

climber
Yosemite Valley
Topic Author's Original Post - Mar 29, 2009 - 11:09pm PT
FYI

A very large rock fall occurred from Ahwiyah Point near Half Dome at 5:26 am on the morning of March 28. The rock fall originated near the summit of Ahwiyah Point and fell roughly 1800 feet to the floor of Tenaya Canyon, striking ledges along the way. Debris extended well out into Tenaya Canyon, knocking down hundreds of trees and burying the southern portion of the Mirror Lake loop trail. Reminiscent of the 1996 Happy Isles rock fall, there appears to have been a small airblast associated with impact on the valley floor. Fortunately, due to the event occurring in the early morning, there were no injuries. The impact generated ground shaking that was recorded by numerous seismometers across California, registering as the equivalent of a local magnitude 2.5 earthquake:

http://quake.wr.usgs.gov/recenteqs/Quakes/nc40233925.htm

The volume of the Ahwiyah Point rock fall is still being determined, but it was clearly one of the largest rock falls in the past decade; for perspective this rock fall was many times the size of the recent October 2008 rock falls behind Curry Village. Numerous smaller rock falls have occurred from Ahwiyah Point since the initial failure, and the southern portion of the Mirror Lake loop trail remains closed until further notice.

Greg Stock
Park Geologist
(209) 379-1420
greg_stock@nps.gov
Gary Carpenter

climber
SF Bay Area
Mar 29, 2009 - 11:18pm PT
Thanks for the info. Greg.
Dapper Dan

climber
Menlo Park
Mar 29, 2009 - 11:19pm PT
COOL !

can't wait to see some pics

glad no one was hurt .

I wonder if it was in the vicinity of hidden falls?
neebee

Social climber
calif/texas
Mar 29, 2009 - 11:20pm PT
hey there... say, thanks for the info... i dont get up there, naturally, but i like to keep in touch... as some much family and childhood connection has been there for me...

thanks for sharing, as the climbers sure can use updates...
Lynne Leichtfuss

Social climber
valley center, ca
Mar 29, 2009 - 11:33pm PT
So what does all this movement over the past year mean in the big picture......Predictions for the next several years ? lrl
Doug Robinson

Trad climber
Santa Cruz
Mar 29, 2009 - 11:34pm PT
Thanks Greg. We are sure benefitting -- our community -- from you being on board with timely info, accuracy and interpretation. Much appreciated.

It's exciting when our so-solid Valley turns once again from place to process.
Ed Hartouni

Trad climber
Livermore, CA
Mar 30, 2009 - 12:59am PT
Walleye, did you get the dates right?
also, not clear what I'm looking at in the photos...

Finally, I guess I should reconsider the climbs on the obscurity list over there.

[edit] I see it now in the background... thanks!
gstock

climber
Yosemite Valley
Topic Author's Reply - Mar 30, 2009 - 11:57am PT
Wow, these posts get buried fast! Bump for geology in action.

Lynne, based on detailed volume calculations of the talus beneath Yosemite's cliffs, all of which has accumulated in the past 17,000, there is little evidence to support the perception that rock fall rates are increasing. What has increased is our ability to record, document, and communicate these events.

As far as predictions, I predict there will be more rock falls.

Greg

cleo

Social climber
Berkeley, CA
Mar 30, 2009 - 12:30pm PT
Thanks Greg -

Is there access to Snow Creek Trail?

-Val
JEleazarian

Trad climber
Fresno CA
Mar 30, 2009 - 12:31pm PT
Wow! I'd actually had the Harding/Merry route on my tick list of obscurities (See, Ed, you aren't the only one hunting these things!). I guess I'd better reconsider.

John
Dick_Lugar

Trad climber
Indiana (the other Mideast)
Mar 30, 2009 - 12:33pm PT
Old lines die and new lines are born...
Capt.

climber
some eastside hovel
Mar 30, 2009 - 01:12pm PT
Thanks for the info Greg.Glad to see you're still over there.I'm looking you up next time I'm on that side.Once again,thanks for keepin' us posted.

Kirk Sager

PS-When we doin' Swiss Arete?
Chris McNamara

SuperTopo staff member
Mar 30, 2009 - 01:14pm PT
i put this on the homepage

http://www.supertopo.com
tom woods

Gym climber
Bishop, CA
Mar 30, 2009 - 01:55pm PT
meanwhile the locals are busy with new first ascents on the boulders.

Seriously, a big ol' rock came down by the folly around 1999, landed square in the middle of the road. It had multiple new routes on it with in a day. Then the road crew blew it up.
SteveW

Trad climber
The state of confusion
Mar 30, 2009 - 02:12pm PT
Holy kiboly!
That's amazing--and it's incredible but wonderful that
no one was in the area and/or hurt, killed, etc.
Jaybro

Social climber
wuz real!
Mar 30, 2009 - 03:11pm PT
I have it on pretty good authority tht the whole thing is going to collapse, Lynne. wish I could name my sources...



=)
scuffy b

climber
4 to 8
Mar 30, 2009 - 03:16pm PT
There was a nice avalanche just east of Widow's Tears on
Saturday. I heard another earlier but didn't see it.

Adamame

Trad climber
El Portal
Mar 30, 2009 - 04:23pm PT
I climbed the Column on the 26th and arrived on Dinner Ledge a few hours after the rockfall. A few friends witnessed it earlier that morning from the ledge. They said it looked like fireworks! As the rocks disintegrate I guess they spark. Rocks continued to fall all weekend and we also witnessed a fireworks show from the Dinner Ledge Viewing area during the next night.
gunsmoke

Trad climber
Clackamas, Oregon
Mar 30, 2009 - 04:35pm PT
Here's a rebalanced version of Walleye's before/after pictures:
Gary

climber
Desolation Basin, Calif.
Mar 30, 2009 - 04:40pm PT
Paging Juan de Fuca, paging Mr. Juan de Fuca...
hoipolloi

climber
A friends backyard with the neighbors wifi
Mar 30, 2009 - 05:12pm PT
Hey Guys! Pretty Excited because my buddy and I were up on The Column when this happened! I got to see it first hand. It was totally spectacular and really massive!

It first woke me up while sleeping on dinner in the middle of the night, early morning hours. I woke up to hear some rock fall, jerked awake and looked around quickly spotting the rock fall. The first time it woke me up it was a pretty large fall coming down the side, the sparks at the lead end of the smoke cloud were what really blew me away. After it hit the floor I looked around a while then fell asleep.

This process went on for what seemed like all night. I kept waking up to small-ish falls coming down in a similar fashion. Then at the pre-dawn hours I woke to a HUGE cannon fodder of a boom, jerked up, looked over to see the entire side of Ahwiyah point shrouded in a massive dust cloud falling down, the lead end looked like a massive fireworks show. When it slammed into the floor it crashed down into a huge ploom of dust that went upwards nad pushed out all the way across the valley floor.

It was pretty amazing. I am stoked to have been able to see it (and fire Southern Man). Thanks for the info Greg.

cheers
scuffy b

climber
4 to 8
Mar 30, 2009 - 05:58pm PT
What a seat for a show like that.
ron gomez

Trad climber
fallbrook,ca
Mar 30, 2009 - 06:08pm PT
A sight only a climber could see! Cool, how lucky to see that while on the rock. Looks like a BIG slide in the photo.
Peace
Brendan

Trad climber
Yosemite, CA
Mar 30, 2009 - 07:59pm PT
Apparently, the fireworks/sparks that we all got to see that next night (after the first big fall) were caused when quartzite crystals rub against other quartz crystals, it causes electrons to be exchanged and create a potential difference. Exactly like lightning, the electrons jump from one quartz crystal to another and cause a "fireworks" effect as all the rocks tumble down. Totally cool to see, all be it a little unnerving to wake up to in the middle of the night on dinner ledge.
Mighty Hiker

Social climber
Vancouver, B.C.
Mar 30, 2009 - 08:16pm PT
Was this one of the areas that has been photographed at high resolution, and if so, what does it show?

Sounds like a new type of bouldering may be possible there - high objective hazard stuff.
Oplopanax

Mountain climber
The Deep Woods
Mar 30, 2009 - 08:57pm PT
Some of the fireworks you see are just from friction heat. I have seen fresh landslide debris from a large rock avalanche in rhyolite that had heated individual grains enough to form an obsidian rind about 2mm thick on each clast. Likewise, the Barrier rockslide near Whister in the 1850's got hot enough to ignite a forest fire where the debris came to rest.
Dr.Sprock

Boulder climber
Sprocketville
Mar 30, 2009 - 09:11pm PT
What's the Terminal Velocity vs Size chart like?
Could a large chunk break the sound barrier?
Knockin over trees, but lots of trees dying, ready to go over in a good wind.
corniss chopper

Mountain climber
san jose, ca
Mar 30, 2009 - 09:18pm PT
do I have to walk up there to see the blast area or will someone post a pic. Tough weekend. Legs are tired.
Dr.Sprock

Boulder climber
Sprocketville
Mar 30, 2009 - 09:24pm PT
it has been windy, i bet if that J Tree kite guy let out enuff line, the chaz man or whatever his name is...
cleo

Social climber
Berkeley, CA
Mar 30, 2009 - 11:10pm PT
nice eyewitness reports - keep 'em up

(and nice climb too :)
cliffclimber

Trad climber
salem, ma
Mar 31, 2009 - 02:03am PT
I was in North Pines and heard a huge rockfall from that exact area that occurred at approximately 12:15 am. I heard the initial crack, but the massive fall didn't happen until a few minutes later. Afterward I checked my cell phone and it was 12:22. There was third round 2-3 minutes later. The time that earthquake report attached here obviously contradicts what I'm saying. I'd like to see the report from the fall I heard. It was, unquestionably, significant.
le_bruce

climber
Oakland: what's not to love?
Mar 31, 2009 - 02:13am PT

Jealous of you Column parties. That is truly a once in a lifetime experience. Lucky dogs!
Patrick Sawyer

climber
Originally California now Ireland
Mar 31, 2009 - 04:30am PT
Uh, some of you think that the event was coolaboola, but I dunna know. It seems to me that climbing can be extreeeeemmely dangerous, what with huge rockfalls crushing our tiny skulls.

I have been having a rethink here and then had a Pauline conversion. I am switching from rock climbing to milking cobras' and mojave greens' venom - I'll stay away from the tigers and taipans, mambas too. And those kraits.
corniss chopper

Mountain climber
san jose, ca
Mar 31, 2009 - 12:52pm PT
before and after pic of the rockfall in Tenaya canyon
below Half Dome.

Reilly

Mountain climber
Monrovia, CA
Mar 31, 2009 - 12:56pm PT
I hope they re-cycle the timber downed.
corniss chopper

Mountain climber
san jose, ca
Mar 31, 2009 - 01:10pm PT
As a wilderness area no logging is allowed. Looks like many of the trees are buried under the slide anyway and too splintered for
anything but fungus and mold habitat.
Reilly

Mountain climber
Monrovia, CA
Mar 31, 2009 - 01:12pm PT
I was being facetious although I hope the irony of Curry's proximity is not lost. I love the sound of honking car horns in the wilderness, almost as good as napalm in the morning.
Lambone

Ice climber
Ashland, Or
Mar 31, 2009 - 01:35pm PT
Did this take out the Death Slabs approach? Looks a bit farther East.
Patrick Sawyer

climber
Originally California now Ireland
Mar 31, 2009 - 01:39pm PT
Good pix Corniss

SlickWilly

climber
Bridge over Hwy. 2
Mar 31, 2009 - 02:37pm PT
The sound/rumble woke me up from a light sleep in Camp 4 that morning. Dang.
le_bruce

climber
Oakland: what's not to love?
Mar 31, 2009 - 02:57pm PT

Anyone know if the slide debris reached the popular trail that extends from Mirror? Looks like it.
simply theresa

climber
Yosemite
Mar 31, 2009 - 03:29pm PT
According to the Daily Report, the southern portion of the Mirror Lake loop trail is closed until further notice.
GRJ

climber
Juneau AK
Mar 31, 2009 - 03:47pm PT
I hope they recycled the exploded timber in the middle of, what should be, the wilderness? Californians.... Drag that crap into camp four and let the monkeys have a bonfire!
JEleazarian

Trad climber
Fresno CA
Mar 31, 2009 - 04:08pm PT
The rockfall was significantly north of the death slabs.

All of this makes me wonder, though, just what was so wrong with Camps 7 & 15 (aka the River Campgrounds) -- and whether we tax-paying family campers will ever get our Valley campsites back.

John
yosguns

climber
San Francisco, CA
Apr 1, 2009 - 01:25am PT

Just got this uploaded. Aftershock rock fall from Sunday, 2 PMish.
cleo

Social climber
Berkeley, CA
Apr 1, 2009 - 02:28am PT
whoa, cool aftershock photo!
Mungeclimber

Trad climber
sorry, just posting out loud.
Apr 1, 2009 - 03:08am PT

images taken Sunday afternoon 3/29

Argon

climber
North Bay, CA
Apr 1, 2009 - 05:23am PT
Great pictures! Greg - Was Ahwiyah Point known to be slide prone and were there any advance signs.
drljefe

climber
Old Pueblo, AZ
Apr 1, 2009 - 10:11am PT
rumble, smash, bump
sneville

climber
Apr 1, 2009 - 11:20am PT
Nice picture yosguns, did you get that from dinner ledge?
sean
Peter

Trad climber
San Francisco
Apr 1, 2009 - 11:44am PT
Looks like the rockfall will result in a lot more closures around the valley...

http://www.supertopo.com/climbing/thread.html?topic_id=823427
cleo

Social climber
Berkeley, CA
Apr 1, 2009 - 12:06pm PT
SeismoBlog: http://seismo.berkeley.edu/blogs/seismoblog.php/2009/03/30/

Bursting Rocks and Trembling Earth
The seismic waves of Saturday's rock fall were recorded by many earthquake stations. The 33 depicted here are sorted top to bottom by increasing distance from Yosemite. It takes seismic waves longer to travel further distances, hence the "delay" of almost 60 seconds between the arrivals of the waves at the nearest and most distant stations. (Click for larger image.)

Screenshot of computer program showing seismic waves generated by the Yosemite rockfall, sorted by increasing distance.

While most of the Bay Area was rattled on Monday morning around 10:40 am by a magnitude 4.3 earthquake near Morgan Hill, another earthshaking event went almost unnoticed by the public - unless you were in Yosemite over the weekend. Early Saturday morning, a huge mass of rock came crashing down from Ahwiyah Point near Half Dome. Greg Stock, the Park Geologist at Yosemite, writes that the rocks "fell roughly 1800 feet to the floor of Tenaya Canyon, striking ledges along the way. Debris extended well out into Tenaya Canyon, knocking down hundreds of trees and burying the southern portion of the Mirror Lake loop trail... Fortunately, due to the event occurring in the early morning, there were no injuries."

But what happens when tons and tons of granite come crashing down unto the valley floor? Such an impact makes the ground vibrate and thereby creates seismic waves very similar to the ones being radiated by an earthquake. Indeed, on Saturday morning seismic stations all over Northern California and Nevada - as far away as 250 miles from Yosemite - registered these waves. The automatic earthquake location computer for Northern California at the offices of the USGS in Menlo Park picked up the recordings and calcuated an epicenter just half a mile to the northwest of Half Dome - which is actually pretty close to Ahwiyah Point. The program even computed a magnitude for the rock fall: Its impact had the same energy as a magnitude 2.4 earthquake.

While the seismic waves generated by a rock fall can be mistaken for the rumblings of an earthquake, the physics behind the two phenomena is completely different. Most earthquakes are the result of tectonic stress, which has accumulated in the rocks due to the movement of the lithospheric plates. A rock fall happens when the rock has been weakened by weathering. Water, which accumulates in cracks, freezes during the winter frosts. As ice occupies a larger volume as the same mass of liquid water, the freezing ice makes the rock expand and burst - similiar to a water bottle left in the freezer for too long. If such cycles of freezing and thawing are repeated often enough, the rock becomes loose and can break.

These rock bursts are by no means rare in granite world of Yosemite. Last October two rock falls hit some of the tents and cabins in Curry Village. In July 1996 more than 162,000 tons of rock cascaded down more than 2,000 feet, killing one visitor and crushing 500 trees. This blast was also recorded on many seismic stations, although it was somewhat smaller than Saturday's rock fall. After the 1996 event, BSL's Bob Uhrhammer analysed the seismic data carefully and reconstructed the details of the fall (see http://seismo.berkeley.edu/events_of_interest/yosemite/eoi_yos.html);

corniss chopper

Mountain climber
san jose, ca
Apr 1, 2009 - 01:51pm PT
noticed in the pictures that some of the runoff water is flowing on 'top' of the fresh rockfall debris. I would have thought
it would be quite porous and let the water inside the mass and so be invisible.

Suppose this means that enough of the rockfall was smashed to a fine powder to make a partially waterproof surface for the runoff to stay on the surface?
Interesting.


Clint Cummins

Trad climber
SF Bay area, CA
Apr 1, 2009 - 03:45pm PT
Photo of the release area from halfway up North Dome, June 2007:

enjoimx

Big Wall climber
SLO Cal
Apr 1, 2009 - 03:57pm PT
Reply to Dr. Sprock

1. You cant break the sound barrier unless some force beyond the force of gravity is involved. Rockfall doesnt break the sound barrier, unless someone attaches a rocket to the rock and blasts it downward.

2. A rockfal wont reach terminal velocity (usually) because it is sliding down the mountain, hence friction

3. Does a peice of lead fall faster than a feather in a non-air resistant environment? No. Neither does a large rock fall faster than a small rock.

Sure you're a Dr.?
jsb

Trad climber
Bay area
Apr 1, 2009 - 09:41pm PT
Does anybody know if this type of thing is usually seasonal... at least in Yosemite? (i.e. maybe melting ice or the thaw/freeze cycle is responsible for a lot of it?)

I know there was a lot of rockfall on Glacier Point Apron a long time ago... also near Rixon's Pinnacle. Were these in the springtime as well, by any chance?
Dr.Sprock

Boulder climber
Sprocketville
Apr 1, 2009 - 10:19pm PT
1) rocks do break the sound barrier
2)rocks can fall from the top of el cappy and never encounter wall friction
3)free falling rocks will have different impact velocities depending on shape, size and density

no, i am not a doctor, i'm a homo...

Reilly

Mountain climber
Monrovia, CA
Apr 1, 2009 - 11:01pm PT
"rocks do break the sound barrier"

I forgot it is April 1st.

Reminds me of the argument I had with somebody about raising the Kursk submarine from its watery grave. He maintained it didn't weigh 18,000 tons because it was underwater. Right, gravity doesn't work underwater, does it?
hobo

climber
PDX
Apr 1, 2009 - 11:19pm PT
Dr, what is wall friction?
Dr.Sprock

Boulder climber
Sprocketville
Apr 1, 2009 - 11:29pm PT
wall friction is what you get as your colon gets scraped by a wall burger not chased with enuff PBR.

Here is how you break the sound barrier with rocks:

Dr.Sprock

Boulder climber
Sprocketville
Apr 1, 2009 - 11:36pm PT

Hey, how much did Dale Bard weigh?
I want to compare his Terminal V to that of say, a real gorilla like Largo?


philo

Trad climber
boulder, co.
Apr 1, 2009 - 11:46pm PT
DocSprock posted;


"1) rocks do break the sound barrier "

Huh? Sorry they make sound when they break but they don't break
the sound barrier.
Unless they are hurtling in from outer space.

"2)rocks can fall from the top of el cappy and never encounter wall friction"

Yup.


"3)free falling rocks will have different impact velocities depending on shape, size and density"

Nope.

"no, i am not a doctor, i'm a homo..."

OK if you say so. Not that there is anything wrong with that.

Dr.Sprock

Boulder climber
Sprocketville
Apr 1, 2009 - 11:56pm PT
3) Read the small print at the bottom:

philo

Trad climber
boulder, co.
Apr 2, 2009 - 12:02am PT
This sounds like a job for Mythbusters.
hobo

climber
PDX
Apr 2, 2009 - 12:03am PT
What is wall friction? For serious.

Dr.Sprock

Boulder climber
Sprocketville
Apr 2, 2009 - 12:07am PT
Wall Friction is your Brain rubbing against your Skull after I whack you with this:



Cool for campin, it just arrived off of evilvay.
can someone Photoshop a Mumbo Special on there?
One Egg, two Bacons and 4 Sambo Cakes with Tiger Butter?
any other cool gear out there?
non REI?

Werd

Trad climber
Bay area
Apr 2, 2009 - 12:37am PT
OK, I'll bite

You can actually roughly calculate the terminal velocity of a chunk of Yosemite rock to answer whether or not it will break the sound barrier...

Cd of a square = 1.05
Density of Granite ~ 2675kg/m3
Atmospheric ("gas") Density = 1.225 kg/m (at sea level, assuming Temp of 20C {~68F}, relative humidity of 20%)

Speed of sound ~ 340 m/s (using same conditions as above)

I chose a square for calculating drag because it's the most probable rock shape that's easy to find a Cd for; it also makes it easy to calculate it's projected surface area (have to assume the block is not tumbling).

So, just use the formula's previously posted and, voila, you have your terminal velocity of yosemite granite.

(now, does a large boulder falling off one of the walls reach terminal velocity before it hits the ground?--another calculation easily done, but I'm too lazy).

Edit to add other atmospheric pressure and speed of sound
Dr.Sprock

Boulder climber
Sprocketville
Apr 2, 2009 - 12:45am PT
Gee thanks!




Knucklehead!
CF

climber
Apr 2, 2009 - 11:31am PT
just posted some photos of the rockfall at
http://www.myyosemite.com/
corniss chopper

Mountain climber
san jose, ca
Apr 2, 2009 - 02:00pm PT
fattrad - there was some blog'in about concrete dome huts
as a show of 'we're trying to make you safe' protection from boulders zooming down the talus slopes behind Curry.
Better than ordinary canvas.

nice pic of dome unit hotel in Texas
http://i238.photobucket.com/albums/ff319/12eric/rentalconcretedomehotelunits.jpg

tooth

Mountain climber
Guam
Apr 3, 2009 - 06:48pm PT
corniss, that's just going to make it harder to recover the bodies.
GDavis

Trad climber
Apr 5, 2009 - 03:36am PT
Was climbing on the apron friday morning and saw huge plumes of dust and debris fall off the wall and blow all the way up almost to the top of the other side of the canyon. Thing isn't done yet... pictures to be uploaded in a bit :)
GDavis

Trad climber
Apr 5, 2009 - 05:47pm PT

this was quite a bit later when I actually got back down to my pack to fish out the camera.
Clint Cummins

Trad climber
SF Bay area, CA
Apr 5, 2009 - 07:05pm PT
> Where exactly?
>
> My guess...

Actually, all that you circled is still intact. What fell was up at the right corner of what you circled. See Chris Falkenstein's photos for the details (in the section dated April 2):
http://www.myyosemite.com/
cliffclimber

Trad climber
salem, ma
Apr 6, 2009 - 02:16pm PT
Based on the Seismic data, the initial post in this thread misstates the time of the rockfall by nearly five hours. Check me on this people, but the seismic data backs up my earlier comment - that I heard the rockfall around 12:15. However, folks on Washington Column seem to confirm the early morning hour. Anyone got more detail on this?
gstock

climber
Yosemite Valley
Topic Author's Reply - Apr 6, 2009 - 02:43pm PT
Seismic data is reported in Greenwich Mean Time (GMT), not Pacific Standard Time, so the largest rock fall did occur at 5:26 am in Yosemite Valley. However, I don't doubt that you heard a rock fall earlier that night - hoipolloi and others report hearing multiple rock falls that night prior to the largest one at 5:26 am.

I am noting all of these rock falls, and I really appreciate hearing from all of you that heard rock falls before and after the main event. Cleo and I are "listening" for rock falls both seismically and acoustically, so knowing the timing of these events is important for seeing if they show up in our data.

weschrist, the area you've circled for the rock fall source area is too big. I'm not yet photobucket savvy, but I think if you look at Chris Falkenstein's "after" photos compared to the "before" photo you can see that the source area did not extend to the summit of Ahwiyah Point as you have drawn it in. Very large rock fall nonetheless...

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

Mountain climber
Angleland
Apr 6, 2009 - 02:47pm PT
rockfall air blasts can exceed the speed of sound according to this:

Results from the air blast simulations indicate that the second Happy Isles air blast (weak shock wave) traveled with an initial velocity above the local sound speed.

http://cat.inist.fr/?aModele=afficheN&cpsidt=1987361

JEleazarian

Trad climber
Fresno CA
Apr 6, 2009 - 04:31pm PT
Thanks Greg, Wes and all the rest. I was actually contemplating either the Harding/Merry route or something new in that area this summer, under the theory that you don't see crowds on obscurities. I guess you won't see me there, either.

John
GDavis

Trad climber
Apr 6, 2009 - 05:25pm PT
I kept getting spooked by the dumpster-dropping sounds eminating from the DNC.



*BOOOOOM-THUD!*

AAAAAAAAAAUGH!! I'M ON GLACIER POINT!!!!
Oh, nevermind. Just trashcans.
Domingo

Trad climber
El Portal, CA
Apr 6, 2009 - 05:27pm PT
GDavis: I know exactly what you mean. I honestly think they might set off avalanches.
Clint Cummins

Trad climber
SF Bay area, CA
Apr 6, 2009 - 05:51pm PT
Here's my guess on what fell, using an image from the Xrez site:


http://www.xrez.com/yose_proj/Yose_result.html
gstock

climber
Yosemite Valley
Topic Author's Reply - Apr 6, 2009 - 07:48pm PT
That's it, Clint. It's hard to see looking straight on, but there were very large fractures (chimneys!) bounding both sides of that large block. You can see that by zooming in on the xRez photo taken from the Diving Board:

http://www.xrez.com/gallery/yosemite/xRez_yose.html

This event illustrates exactly why we took all of those panoramic photos - a great tool to study rock falls after they've happened!

Greg

gstock

climber
Yosemite Valley
Topic Author's Reply - Apr 6, 2009 - 08:05pm PT
Yep, that's it. Note the trees for scale.
Dr.Sprock

Boulder climber
Sprocketville
Apr 6, 2009 - 09:16pm PT
there is a new crack and a new roof, albeit, a bit unstable at this juncture in time, but nevertheless, worth contemplating.
`
JesseM

Social climber
Yosemite
Apr 7, 2009 - 12:28pm PT
Hey Supertopians,

What an awesome thread! Lots of cool photos, intelligent analysis, and good info. Maybe I'm wrong, but the rock in some of these last "before" photos looks(ed) real solid. Chris or Clint or anyone else, were there any routes over there?

Clarification on closures: The Slabs approach to Half Dome will not be affected by the Southern portion of Mirror Lake loop trail closure. There will be general closure signs, and interpretive signs at the Tenaya Bridge (paved bridge) before the Mirror Lake loop. The Slabs access will remain open.

That said, remember that there has been a lot of rockfall off of the NWF face of Half Dome above the slabs over the last few years. So precede with caution, and consider going the long way through Little Yosemite Valley and up the Half Dome trail.

Another clarification: Peter stated, "Looks like the rockfall will result in a lot more closures around the valley..." This rockfall has not caused any more campground or lodging closures in the Valley. All Yosemite Valley campgrounds are open.

Its great to be back, and I look forward to another season of great threads on the Supertopian forum!

Jesse McGahey
Lead Climbing Ranger
Yosemite Wilderness Management
(209) 372-0360
jesse_mcgahey@nps.gov

WBraun

climber
Apr 7, 2009 - 12:31pm PT
"Death Slabs"

Who came up with this bullsh'it term?.

It was always called "slabs to half dome"

Modern drama queens most likely rename everything ....
Rhodo-Router

Gym climber
Otto, NC
Apr 7, 2009 - 01:05pm PT
"Death" just doesn't mean as much to folks who believe in reincarnation...
JesseM

Social climber
Yosemite
Apr 7, 2009 - 02:21pm PT
Werner, out of respect for your sound judgment on terminology I edited my post to omit the "Death Slabs" term. Maybe the Drama Queen who renamed the Half Dome Slabs lurks somewhere on this forum...?

Jesse
Clint Cummins

Trad climber
SF Bay area, CA
Apr 7, 2009 - 02:32pm PT
Jesse,

Yes, there are a couple of old routes there. Here is the main one:

from

http://www.supertopo.com/climbing/thread.html?topic_id=602007
corniss chopper

Mountain climber
san jose, ca
Apr 7, 2009 - 04:05pm PT

The slabs approach route up to Half Dome is an active rockfall
area.
People pick up beta on Yosemite routes from numerous sources.
Names like Death Slabs makes people wary.

Nicknaming them the Easy Picnic slabs or Frisky School Kids Approach slabs or Happy Bivouac Slabs or Staircase Slabs or
Nude Girls Sunbathing Slabs approach..
..would increase the traffic and the chance of fatalities.


Clint Cummins

Trad climber
SF Bay area, CA
Apr 7, 2009 - 04:11pm PT
Maybe we should rename other stuff, then, too?
Death Capitan?
Death Nose?
Glacier Point Death Apron?
Rixon's Death Pinnacle?

It seems a bit arbitrary on where to draw the line.

I have used the Slabs Approach to Half Dome, and one of my friends had a close call on it with rockfall in the past 2 years. I don't exactly recommend it, but it is an approach option to be aware of.
Rhodo-Router

Gym climber
Otto, NC
Apr 7, 2009 - 04:37pm PT
'Death Slabs' is the first term I ever heard to describe this approach..this would be in the early-mid 1990s I guess, and it seemed to be the generally accepted usage.
east side underground

Trad climber
Hilton crk,ca
Apr 7, 2009 - 05:38pm PT
after my last experince on "the slabs", a dead guy at the base and nearly getting picked off by rockfall I prefer "nude girls sunbathing slabs approach. :)
Mr_T

Trad climber
The 7th Pin Scar on Serentiy Crack
Apr 7, 2009 - 08:00pm PT
I always thought the Death Slabs are the terrain you get into if you try to drop down the North Dome Gully too soon. Half Dome is just the Slabs approach.
Mighty Hiker

Social climber
Vancouver, B.C.
Apr 7, 2009 - 08:05pm PT
Greg/Jesse: What was the total volume and mass of the rockfall? Any estimates?
WBraun

climber
Apr 7, 2009 - 08:12pm PT
LOL Jesse

You know me better n that. You should ah said: "Fuk off Werner, we'll call it anything we want."

Anyways .. Bridwell and a couple of other people including myself back in 72 made our first descent down that thing. Bridwell says hey "I think this thing will go, let's take this shortcut back to the Valley."

Everyone nods yes and off we go.

It's Bridwell. We won't die with him in the lead ...... hahaha
CF

climber
Apr 7, 2009 - 10:01pm PT
check out the gigapan of the rockfall at
http://share.gigapan.org/viewGigapan.php?id=20475
cleo

Social climber
Berkeley, CA
Apr 8, 2009 - 12:17am PT
Nice Gigapan!
T H

Boulder climber
the greasewood ghetto
Apr 8, 2009 - 03:41am PT
Thanks cF
gstock

climber
Yosemite Valley
Topic Author's Reply - Apr 8, 2009 - 03:16pm PT
The cumulative volume of the Ahwiyah Point rock fall(s) was about 43,000 cubic meters, or about 114,000 metric tons. This makes this rock fall larger than the 1996 Happy Isles event. In fact, it is the largest event since the Middle Brother rock fall of March 10, 1987. For perspective, though, the 1987 Middle Brother rock fall was about 600,000 cubic meters in volume, or about 1.6 million metric tons, roughly 14 times larger than the recent Ahwiyah Point rock fall. There were several other notable rock falls in that decade (1980-1989), including the 1980 Yosemite Falls Trail rock fall (volume 1,500 cubic meters, 3 fatalities, 7 injuries), the 1980-81 Elephant Rock rock fall (volume 24,000 cubic meters), and the 1982 Cookie Cliff rock slide (volume 100,000 cubic meters). In terms of both rock-fall volume and the number of rock fall-related injuries/fatalities, the period 1980-1989 was much more significant than the period 2000-2009 has been.
JesseM

Social climber
Yosemite
Apr 8, 2009 - 06:37pm PT
Clint,

Thanks for the route info. It looks like most of the route is still intact...I wonder when it will see its next ascent? Hahaha...hopefully not for a few decades at least! On the other hand folks, still climb the Good Book all the time, but it was popular before the middle brother rockfall.

In other news, Werner and I had a long talk this morning about the merits of "Death Slabs" vs. simply the "slabs approach to Half Dome." Neither seemed to adequately fit the place. So we decided to rename it, "The Approach Slabs that may cause death or serious injury." I am now writing to our official records keeper to notify him of the change. After processing we should have a new designation in a couple years...as long as no one sues us over it.

-
J. McGahey
Sean Jones

climber
Apr 8, 2009 - 06:50pm PT
Glad no one was hurt. Aside from that, I love when these huge rockfalls go down. Just like the rest of life. Even when things seem solid. It's only temporary. Another reminder to be glad for what you have while you have it. Anything can change in a split second.

S.
Clint Cummins

Trad climber
SF Bay area, CA
Apr 8, 2009 - 06:56pm PT
Jesse,

I think you meant:

> On the other hand folks still climb the Good Book all the time, but it was popular before middle brother rockfall.

But I think there were separate rockfalls, earlier affecting Koko Ledge and the left side of Rixon's, then more recently affecting the Good Book. (Although I think there were also earlier ones in the vicinity of the Good Book).

I suppose the Slabs Approach naming became controversial, because it was not in a guidebook, so people used what ever name they heard most recently. I have also heard it called the Mirror Lake Approach. The 1987 guidebook says "A quicker, more direct, yet very devious approach can be made from the vicinity of Mirror Lake." (no mention of the word "slabs" in the description).

The 1982 guidebook mentions "death slabs" in a description of the North Dome gully descent, p.126.
scuffy b

climber
Frigate Matilda
Apr 8, 2009 - 07:02pm PT
The Mirror Lake area related approach slabs which may cause
death, serious injury or even MUCH THIRST if things go less
than perfectly.

Some minor tweaking could improve the acronym potential, I'm
sure.



I'll go sit in the car now.
JesseM

Social climber
Yosemite
Apr 8, 2009 - 07:38pm PT
Thanks Clint. Now edited. I'm glad you knew what I was talking about. Being from North Carolina I still mix up the names of our classic 5.11, The Open Book in Linville Gorge, and the Good Book, AKA the Right Side of the Folly.

T H

Boulder climber
the greasewood ghetto
Apr 9, 2009 - 03:27am PT
On the Gigapan image you can see a water-course both on the wall and in the new talus that flows past the right side of the rockfall . That thing (freezing/expanding) may have been the trigger .
randalms

Trad climber
ca
Apr 9, 2009 - 11:58am PT
Excellent gigapan picture of the rockfall.


http://www.gigapan.org/viewGigapan.php?id=20475&window_height=787&window_width=1262
Ed Bannister

Mountain climber
Riverside, CA
Apr 16, 2009 - 06:03pm PT
i love the smell of ozone in the morning
bluering

Trad climber
Santa Clara, Ca.
Apr 16, 2009 - 06:36pm PT
Those gigapan's are so awesome. Amazing.
snowey

Trad climber
San Diego
Apr 27, 2009 - 03:12pm PT
Just ran across this article:
http://www.mercurynews.com/nationworld/ci_12237081
cleo

Social climber
Berkeley, CA
Apr 27, 2009 - 07:04pm PT
Busted!

The article originated at the Fresno Bee:
http://www.fresnobee.com/local/story/1358041.html

(thank you to everyone who has helped along the way, including other Supertopians who came to the field and those who've been reporting rockfalls right here)
Mighty Hiker

Social climber
Vancouver, B.C.
Apr 28, 2009 - 12:52am PT
I'll try to post the photos I took of Ahwiyah Point and the deposition area from Snow Creek trail last Wednesday, tomorrow.
Dr.Sprock

Boulder climber
Sprocketville
Apr 28, 2009 - 01:43am PT
this mite be a tripout, Elephant Rock:

"of two rockfalls, totaling nearly 50,000 m3, that took place in 1971 and the winter of 1980/1981 (Wieczorek et al., 1992). According to second-hand accounts, live trout were scooped off the road surface after the river splashed onto the highway."
Chris McNamara

SuperTopo staff member
Apr 28, 2009 - 10:24am PT
here is a photo i just took from the top of el cap that shows the rockfall pretty well

snowey

Trad climber
San Diego
Apr 28, 2009 - 12:00pm PT
Chris,
How did you get to the top of El Cap?
Any good stories/routes?
Mighty Hiker

Social climber
Vancouver, B.C.
Apr 29, 2009 - 12:20pm PT
Here are some photos of the rockfall and area, from the Snow Creek trail. Taken Wednesday 22nd April. The first rockfall was 28th March, and Werner told me there was another one on 18th or 19th April. They even had to rescue some tourists from the closed area. I went up the trail to the bridge (about 2,000 m) for some exercise, to see some natural wonders, and maybe if I got lucky to got some pictures of further rockfall.


(Bump, for Jesse and Greg.)
cleo

Social climber
Berkeley, CA
May 5, 2009 - 12:52pm PT
I thought I'd share my (new) webpage here, in case any of you are interested in learning more.

http://research.eerc.berkeley.edu/projects/seismicrockfall/
T H

climber
Aug 2, 2010 - 09:25pm PT

The new Sentinel Dome cam shows the rockfall location pretty well now .
http://www.yosemite.org/DSN/wwwyosemiteassociationorg/Content/Webcam/sentinel.jpg
franky

Trad climber
Ford Pickup Truck, North America
Aug 2, 2010 - 09:36pm PT
I hiked across the rockfall fairly recently, and it is true, the wood is fragrant. It is pretty impressive.

I wonder why it is still closed... it seems to me that the area shouldn't be any more dangerous now than it was before the closure.

is there some evidence to suggest it is any more dangerous than any other trail near a wall of the valley? Is it closed just because the trail hasn't been rebuilt? Waiting for the talus to stabalize?

hmmm.
PAUL SOUZA

Trad climber
Clovis, CA
Aug 2, 2010 - 09:51pm PT
On July 25th, we were walking across the meadow across from Curry Village. We thought we heard thunder as there was earlier that day when we were rapping off the Royal Arches. After we crossed the road headed to Curry Village, we saw a huge dust cloud in front of Half Dome. Don't know if it was in the same previous areas.
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