I remember heading up toward La Escuela in the early 1970's, and the base of the southwest face of El Cap looked like someone had bombed it. I believe that particular rockfall was from a couple of pitches of the Heart Route.
I am rather surprised that the Three Brothers, and particularly the east side of Lower and Middle brother, are not higher on the list. The area to the left (southwest) of Rixon's Pinnacle has always been known as a bowling alley, and I remember rockfall around The Folly that added another Bear Rock sized boulder or two to the talus field.
In any case, those pictures of the Middle Cathedral rockfall made me wonder if Thirsty Spire or The Turret are still attached. Ever since Sentinel Spire bit (or, more accurately created) the dust, I've always wondered about last ascent possibilities.
Edit: Checking Greg's reference to the thread on the Heart Route confirmed that the rockfall came from that route. Apparently, the white tower (aka Tower to the People) and some associated pitches simply fell off.
You could do a totally non-invasive 3D seismic survey of the entire valley. Now the geophones are wireless and the energy source could be vibraseis on the roads.
I've never seen a 3D shoot of anything like this, especially with the velocity problems that you will get with talus, which could be large. Weathered zones such as any alluvial deposits are really tough to correlate. It would be interesting.
In the meantime, yep, El Cap has huge talus depostits on both sides of the Nose. If you have ever humped the approach all the way to the W Buttress, you have to go uphill a long way.
Things that are above sea level are always heading downstream and downhill. I would love to work on the stratigraphy of the glacial and alluvial deposits in Yosemite.
those pictures of the Middle Cathedral rockfall made me wonder if Thirsty Spire or The Turret are still attached.
They're definitely still there and not coming off anytime soon.
If one of them came off, the road would be blocked.
A good reference for comparison are the July/September 2011 rockfalls which came off the North Face, slightly left of Mother Earth.
They generated a lot of dust and deposited a lot of small rocks/gravel all along the base when the source flakes disintegrated on the way down.
Photo taken about a minute after the rock fall. A slight breeze was blowing and it's blown the dust up high more to the east/left side of the NW face.
But Greg's photos pinpointed the sources as some relatively small flakes.
Middle Cathedral Rock rockfall source area after the 5 July 2011 rockfall.
In the 90s I was at the base of El Cap and saw a very similar (to 3/2013) rockfall come down the North Buttress of Middle, with lots of dust. It was sobering, because we were planning to do the route in the next day or two. We made other plans. :-)
In the late 80s I saw some boxcar sized blocks come down the middle of the North Face from the band of overhangs up high. Big impact craters at the base.
The height from which the rocks fall in the Valley is another dimension to the rockfall risk (besides frequency and volume).
It leads to devastation at the base!
I'm amazed that Middle doesn't just fall over some time. It was always my favorite rock by I cut back my time on the big faces there after Billy Westbay got beaned one time when we were on the DNB and Kauk and I almost got cleaned off Stoner's by a big ass rock slide from the U-Shaped Bowl. We were down low and I rapped off the rope to the ground and just took off running, right off the end of the line as sh#t continued raining down.
Sometimes Middle around Stoner's is as quite as a mouse. Sometimes a couple of basketballs come down there without any warning. Just keeps you on your toes. But then there's that north apron area . . . big stuff waiting to happen.
I - that is: "Willy and I": - have had quite a few footballs and toasters sail past us on the MCR Apron over the years. It's very important to remain focused when these UFO's come hooting past 'yer run.
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.
You don't have to be Matthes to realize that, some day, the entire Valley shall be refilled into the vee-shaped river gorge whence it came; I've seen some of the geotech's maps of the max talus outfall zones, which seem to exclude only Sentinel Beach - and scarcely so, at that.
Question on point seems to be: is this going to occur before Tioga opens this season?
One day in the mid 1960's, Jim Mays returned to Camp 4 on his old bicycle with wide eyes and rock dust in his hair. He came up to my camp by the Wine Boulder and told about riding down the road towards El Capitan past Rixon's Pinnacle, when boulders the size of semi-trucks started bounding down across the road all around him. Some rather large pot holes were punched into the road and some boulders blocked the road for a while. We walked back there together and he showed me the fresh rock fall boulders.
I've mentioned earlier about experiencing a major rock fall coming down all around us on Dolt Tower in 1985.
Another day in the early 1960s I walked from Camp 4 up to the base of the Nose of El Cap early in the morning after a big ice storm. When the sun hit the upper face, large sheets of ice started melting and falling down directly towards me, fluttering around like heavy falling maple leaves. On either side of me there were great slabs of ice crashing into the forest. Those that came directly down the nose were pulverized by impact with the rock and reached me as a shimmering curtain of ice crystals in the sunlight.
I've spent many days on Glacier Point Apron and on the Cathedral Rocks without any recollection of rock fall.