The plastic flow of rock reminds me of a related question: How high can a cliff face be before the weight of the rock above causes the face to blow out. For hard rock (granite, sandstone, maybe limestone) it is obviously pretty high, like on the order of several thousand feet based on El Capitan, the Venezuelan tepuis and Mount Thor.
Mark Minton From: Texascavers [mailto:texascavers-boun...@texascavers.com] On Behalf Of Dwight Deal Sent: Tuesday, June 2, 2020 6:49 PM To: Cave NM; Cave Texas Subject: Re: [Texascavers] here's a fun use of the underground -----------snip----------- At Gnome and the WIPP the cavity is a half-mile down. Now, I ask, how much does a half-mile of rock weigh? The right answer is "a whole lot"! Under those confining pressures (the weight of the overlying rock) the salt IS plastic, and readily deforms. If you excavate an opening at atmospheric pressure, the salt immediately starts to flow into it, like thick, slow toothpaste from a squeeze tube.
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