We used a geographic technique called ground penetrating radar (GPR). I have been using this technology for a year now and it is one of the best ways to analyze subsurface stratigraphy. We use this technology to non invasively see how layers have been built upon each other over thousands of years. So you can guess why we used it. We were(/are) looking to uncover more information about the geologic history of the area: specifically in the valley.
But this moraine has an interesting story to it. In the early human development of Yosemite Valley, flooding was a big problem. The merced river would tend to get backed up behind the moraine and flood out everything. Bugs were also a big issue as the area would get almost swampy. To rid themselves of this problem, park officials blew up the moraine to make way for the Merced River. Fast forward a century and some change and we get the picture below.
(erosion)
That is a significant amount of erosion in a relatively short amount of time. It's interesting to have evidence of something we have changed for our convenience, to have it come back and bite us.
Since we now see that this is a problem, park officials want to restore the El Cap moraine and build it up to its original state. But here is the moral question: Is it better to restore the moraine and deal with floods? Or to not touch the moraine. Its an easier question without knowing that this park attracts around 4 million tourists annually, bringing in an insane amount of money.
I realize this isn't as directly hazard related as other posts, but I think it deals with the same relationship we find in other situations. Risk v. benefit. Oh and here's an ad that I am in for GPR equipment. Coming to a geophysics magazine near you!
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| I'm the third GPR professional from the left holding one of the antennae. Credit to Harry Jol for the photography! |
