470 degrees C in open vents above a (presumed) magma dome at > 3000 metres deep on the mid Atlantic ridge. Water is supercritical at these temperatures and pressures. http://environment.newscientist.com/article/dn14456 Russell McMahon -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist