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Yosemite closures 15-Jun-2012 At 3:15:49 PM Doug

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On 15/06/2012 pmonks wrote:
>On 15/06/2012 Doug wrote:
>>But what else
>>could they do? Any perceived threat as detailed by a geologist employed
>>specifically for the purpose of assessing potential danger would have
>to
>>be acted upon.
>
>The link you posted above ...
I didn't post the link, Stugang did.
...makes no mention of Camp 4 or environs at all,
>only Glacier Pt (which I agree is a scary place - only climbed there once
>but it was pretty spooky to hear about the 2008 rockfall).
>
>Like I said, there are no big cliffs close to Camp 4 - in fact directly
>behind it is the gully / scree slope that the initial switchbacks of the
>Upper Yosemite Falls Trail go up. A little suspicious that they'd be closing
>parts of Camp 4 due to rockfall danger without also closing that (popular!)
>trail...
I don't think there is a conspiracy at work here.
Direct quote from the report:
"Yosemite National Park and USGS scientists, in collaboration with academic geologists, recently completed a comprehensive study of rockfall hazard and risk in Yosemite Valley. This internationally peer-reviewed study utilized new data and technologies to map the cliffs and talus slopes, date ancient rockfalls, and perform computer simulations of potential future rockfalls. This information was used to identify a rockfall hazard line on the valley floor. Existing structures within this line were evaluated using a numerical "risk metric" that quantifies the risk posed to human life and safety. This study represents the first time that rockfall risk has been quantitatively assessed in Yosemite Valley.   ...
...The information in the study was adopted by Yosemite National Park this month ...

And here is an image from the actual report:

It looks like there has been considerable rock movement around Camp 4, some of which probably has resulted in the "gully/scree slope" of which you speak. (I'm not a geologist, but those who collaborated on the report clearly are in the upper echelons of that profession). One probably needs to read the full report (http://www.nps.gov/yose/naturescience/upload/Quantitative-rock-fall-hazard-and-risk-assessment-for-Yosemite-Valley-April-2012.pdf) but in the end I think unless you're a geologist you'd probably have to accept that the NPS, on the advice of expert geologists didn't really have a choice to close any areas that were concluded to be of a high risk level. In regards to leaving the trail open, I don't really have an answer for that except that maybe because it's a trail rather than the campsite the risk at any one time of someone being injured is less?