[Geysers] The role of geyserite in geyser plumbing (or "Who needs geyserite anyway?")

[Davis, Brian L.]

Why do you need geyserite to ‘pressure seal a geyser’?

We had an interesting conversation on Facebook recently about how a geyser erupts, and I managed to get myself somewhat confused (again). I was trying to point out that the pressure in a geyser conduit is never really above hydrostatic - pressure does not “build” in a geyser (at least not after it is full), and during an eruption the pressure in the conduit decreases. A lot. So I started working up a text description of an eruption in detail (right down to how bubbles of steam grow, etc.).

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…

1) Is the pressure always at or below hydrostatic?
2) If so, what role does a geyserite-lined system play (vs. any other lining)?

To anyone interested in the original longish conversation, here’s a FB link to it:
https://www.facebook.com/groups/4939307398/permalink/10151566192312399/

This includes links to data from models that show the pressure never gets above hydrostatic *except* during rapid dynamic effects (like a steam-filled conduit sealed under a deep pool condensing the steam and producing a post-eruption ‘water hammer’):
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=3695302

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.

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Brian Davis
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