<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML XMLNS:O><HEAD> <META content="text/html; charset=UTF-8" http-equiv=Content-Type> <META name=GENERATOR content="MSHTML 10.00.9200.16635"></HEAD> <BODY id=role_body style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; COLOR: #000000" bottomMargin=7 leftMargin=7 rightMargin=7 topMargin=7><FONT id=role_document color=#000000 size=2 face=Arial> <DIV>With some snips taken out of Brian's original posting, here are a couple of brief thoughts:</DIV> <DIV> </DIV> <DIV>1. Clearly, "geyserite" (that is, silica) is not absolutely required as a plumbing system lining. Though mostly of rather small size, there are a few geysers/erupting things here and there that are lined with carbonate. Geyserite is the more common material simply because these high-temperature systems tend to occur in youthful volcanic areas where silica-rich rocks predominate. Also, there appear to also be some geysers that are not lined with anything at all other than country rock. Like Norris (speaking of Steamboat!), where there is little to no geyserite in many of the features; indeed, at Norris clays might play this role.</DIV> <DIV> </DIV> <DIV>2. I think Brian hit on it where he said "...  that it acts to reinforce and pressure-seal the main conduit against higher *external* pressure..." There are several notable cases where geysers exhibit clear-cut seasonal variations in their activity (Aurum; Fan & Mortar; Giant...) because of, we presume, the influx of groundwater from the surrounding external environment. So perhaps the key is that geysers aren't so much sealed in as they are sealed out.</DIV> <DIV> </DIV> <DIV>Scott Bryan</DIV> <DIV> </DIV> <DIV> <DIV>In a message dated 7/31/2013 6:27:17 P.M. US Mountain Standard Time, brdavis@iusb.edu writes:</DIV> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial> <DIV style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma; COLOR: #000000; DIRECTION: ltr"> <P class=MsoNormal>Why do you need geyserite to ‘pressure seal a geyser’?</P> <P class=MsoNormal>Then I thought about the description of the role geyserite plays in “pressure sealing” the “plumbing systems” of geysers… and wondered “why?” As near as I can tell, pressures never rises above hydrostatic. Moreover, if the plumbing system was actually ‘sealed’, there would be no way to recharge either water or energy to the system. So…</P> <P class=MsoNormal>1) Is the pressure always at or below hydrostatic?<O:P></O:P></P> <P class=MsoNormal>2) If so, what role does a geyserite-lined system play (vs. any other lining)?</P> <P class=MsoNormal> <P class=MsoNormal><O:P></O:P></P>So far the best idea I’ve come up with is that it acts to reinforce and pressure-seal the main conduit against higher *external* pressure, after the geyser has erupted… but honestly that doesn’t make a lot of sense to me, as water infiltrating from the walls seems to be one way the conduits refill in the first place, and secondly voids in rock or even semi-consolidated sediment can remain against hydrostatic external pressure just fine on their own, no “armor cladding” needed. <P></P> <P class=MsoNormal>Brian Davis<O:P></O:P></P></DIV></FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>