Monday, October 11, 2010

Rock Fall Near El Capitan in Yosemite Today

Your on-the-spot geological reporter was on the scene and on the job today when a rock fall occurred on the cliff just east of El Capitan in Yosemite Valley. Well, ok, I was almost on the scene, and almost on the job...to be honest, I was near the top of Sentinel Dome on the south rim of the valley, eh, dozing on the smooth granite slope. I was listening to what I thought was an odd-sounding jet off in the distance, but when the sounds abruptly stopped, I thought "rockfall!". I ran to the edge of the cliff just in time to see the dust rising from the tumbling boulders.
There has been little in the way of official information as of yet, but it seems to have originated in the vicinity of the cliff at Horse Tail Falls, the high vertical wall just east of the main cliff of El Capitan. I only had time for a cursory examination, but I think the impact point is the white rock on the cliff just above the tips of the trees.

There are white streaks on the dark gray cliffs above the white rock that may be impact scars(click on the photo below for a larger image), and lots of fresh looking boulders on the slope below. I can't tell if trees were snapped off or not. I would appreciate any reports or additional from climbers, hikers, or anyone who was in the meadow below. I will gladly post any pictures, too!
Once a big chunk of rock breaks off a cliff, nearby rocks may be destabilized, and subsequent rock falls are possible. Clearly the climbers know this...