Ahwiyah Point Rockfall

If a rock falls in the wilderness, but no one hears it, does it make a noise?

I got back into the office today after my trip to the Bay Area and eventually heard that there had been another substantial rockfall in Yosemite early Saturday morning (March 28). The NPS Geologist made a statement, posted it to Supertopo.com, and the story has been picked up here and there by news organizations, and blogs, but didn’t have much widespread coverage. The AP finally picked up the story today – 3 days after it happened.

The rockfall was substantial. The volume is still being determined, but is estimated to be “many times the size of the recent October 2008 rock falls behind Curry Village”, and caused enough ground shaking that it was registered as the “equivalent of a local magnitude 2.5 earthquake”. Smaller falls continue to rain down occasionally and the Park Service has closed the southern part of the Mirror Lake Loop until further notice. However, many Valley residents and visitors didn’t even notice and hadn’t heard about it.

What if that rock fall had occurred one canyon over? Would anyone at all have noticed? Would it have been news? Everyone hears about the plane crashes, but meanwhile, 39,800 motor vehicle related deaths in 2008 is the lowest rate since they started recording the information in the 1920s. If you’re interested in looking around for things to be nervous about, you can find them everywhere.

The Park Geologist made an interesting comment further down in the SuperTopo forum thread in response to questions about the various rockfalls that have been hitting the media lately. It made me smile. He says “…based on detailed volume calculations of the talus beneath Yosemite’s cliffs, all of which has accumulated in the past 17,000 [years], 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.”

So, gravity will continue to work, but in the meantime, if you’re looking for things to worry about – watch out for the squirrels