Here's some more thoughts on the arch that "went missing". http://crosscut.com/blog/#16664
T. -----Original Message----- >From: Gill Ediger <[email protected]> >Sent: Aug 11, 2008 5:27 PM >To: [email protected] >Subject: [Texascavers] Freeze/thaw collapse > >At 11:00 AM 8/11/2008, Louise Power wrote: >>On the news this weekend, they called it "geology at work." Hope >>nobody was hiking underneath when it happened. > >When Mt. St. Helens blew up people were all agast at the devistation >and destruction and how terrible it was to human and animal life. >That's a pretty biased and one-sided view and a slap in the face of >geology which was hard a work just tending to normal business. > >I call it "land building"--geology at work, doing what it's supposed >to be doing: Building mountains and then moving them to the sea--one >grain at a time if need be. Geology doesn't give a damn if anybody >was hiking under the arch at the time it fell or not. People are >mostly insignificant vectors in the overall scheme of geologic >things--they help out a bit by tumbling rocks down the hillside >(getting them closer to the sea) whilst road building or just hiking, >or they throw rocks into the river whilst entertaining themselves >skipping stones. Otherwise human beings are of little concern in >geologic time or to geologic forces. Future limestone will contain >rubber tires and lost boat motors and mafia exiles encased in >concrete blocks--stuff like that. > >Freeze/thaw cycles on the surface of the rock play an important part >in the first stages of rock degradation there, Fritz. At least in >places where it freezes--like Utah. But you can't discount the daily >expansion/contraction due to the temperature changes in the ambient >atmosphere around the arch when considering what actions weakened it >enough to make it fall. Daily expansion and contraction (over a range >on the order of 50 or more degrees) would, I think, play a lot larger >part in the eventual blowing apart of a (nominal) monolithic chunck >of extremely exposed sandstone along internal joints and other zones >of weakness by eventually crunching itself into smaller and >subsequently insubstantial pieces, at some point being unable to >support itself any longer. > >That global warming (even though it was introduced to this discussion >as a subtle joke unnoticed by some humor impaired readers) could have >a very real effect on the differential values of expansion and >contraction due to thermal changes in the dynamic atmosphere must be >considered, and in a big way--no matter what is causing global >warming this time around. > >Doing my part for global warming, >--Ediger > > >--------------------------------------------------------------------- >Visit our website: http://texascavers.com >To unsubscribe, e-mail: [email protected] >For additional commands, e-mail: [email protected] > http://home.infionline.net/~tbsamsel/ --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
