Do remember, of course, that these figures are only the "plumb-able" depths. The plumbing systems per se are estimated (in the Firehole Basins, anyhow) to extend to a depth of around 400 feet. Which is rather longer, and more voluminous, and better insulated than your 12 feet. Scott Bryan In a message dated 10/4/2009 5:34:54 P.M. US Mountain Standard Time, brdavis at iusb.edu writes: surprises me how shallow some of these are; -------------- next part -------------- An HTML attachment was scrubbed... URL: </geyser-list/attachments/20091004/e747186b/attachment.html>