[Rockhounds] Something going on in Yellowstone

[Kreigh Tomaszewski]

Or take a look at the Wiki article at 
http://en.wikipedia.org/wiki/Yellowstone_supervolcano



On Thursday, Jan 1, 2009, at 12:31 America/Detroit, Tim Fisher wrote:

> It has happened many times with the same hotspot. Google McDermitt 
> caldera.
>
> -----Original Message-----
> From: rockhounds-bounces at lists.drizzle.com
> [mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of Dora Smith
> Sent: Thursday, January 01, 2009 6:28 AM
> To: J Bryan Kramer; Rockhounds at drizzle.com: A mailing list for rock 
> and gem
> collectors
> Subject: Re: [Rockhounds] Something going on in Yellowstone
>
> I'm the original not expert.  I learn something totally new about it 
> every
> five minutes.   I did learn in teh course of reading through some of 
> that
> stuff that apparently the basalt flows predate the hot spot eruptions, 
> some
> ancient - shield volcano?
>
> I've no idea when such a thing happened in North America.    And to be 
> more
> confusing I got the impression that there were more ordinary eruptions
> before that happened.   Not Earth didn't have an entire history before 
> teh
> end-Permian extinction, and there was a smaller flood basalt eruption 
> in
> India at the end of the Cretaceous, but I keep thinking that a flood 
> basalt
> eruption in North America must coincide with the development of the 
> crust
> itself if I never heard of it before.
>
> But it sounds like you're not familiar with the Yellowstone caldera at 
> all.
> This is a very different type of volcano, and they only came to 
> understand
> it since I graduated from college 30 years ago.    VERY recent.  Hah, 
> hah,
> hah.    Santorini, the volcano that may be associated with the Exodus
> phonemena, was of this sort, and so was the eruption of Toba in the
> Phillippines 75,000 years ago that brought the human race to the brink 
> of
> extinction.   Not a flood basalt, but the next biggest monster.    
> Sometimes
> very thick magma builds up in a huge, abscess-like crater underground 
> under
> such conditions that it can't easily erupt to the surface.    When it 
> does
> that's a problem enough - you get pyroclastic flows and ash clouds that
> travel some little distance.   Like in Pompeii, and Mt. St. Helen's.
> But large caldera volcanoes erupt rarely and alter Earth's history 
> when they
> happen.    If Yellowstone blew it would kill all life on half the North
> American continent and the climate changes would  starve nearly 
> everyone
> else on the planet.    Problem is it's due to blow and pressure is 
> building
> up, and noone knows how much pressure has to build up or what it all 
> means.
> The cycle of that volcano is in hundreds of thousands of years - not 
> our
> time scale.    Confusing the issue is that the volcano is caused by a 
> hole
> in the Earth's crust that moves over time, relative to I think the 
> North
> American plate.  Unfortunately it hasn't at this time moved out from 
> under
> the last caldera, but it does appear to have moved in a direction 
> consistent
> with its previous movement.   If the volcano significantly changed its
> geology it could conceivably begin to erupt less violently.  Though 
> part of
> the violence is due to the nature of the magma rather than the hard cap
> formed by the previous eruption.
>
> Several years ago I got interested and put together a web page.
> http://www.tiggernut24.com/catastrophes.html   There's an associated 
> page on
> teh geology of Sumatra and subduction faults that isn't relevant to 
> much
> that goes on in North America (except in teh Cascades).
> http://www.tiggernut24.com/earthquake.html   I begin with a link to 
> the web
> pages of a PBS special a few years ago.   And the Wikipedia article, 
> and
> some general geology of hot spots and caldera volcanos.
>
> One thing that complicates the issue is that between the monster 
> eruptions
> every 600,000 to 700,000 years, Yellowstone does have smaller and more
> normal eruptions, and these have left more routine lava flows in the 
> area.
> I'm not yet up on what kinds of volcano flows leave what kinds of lava
> deposits, and it's very relevant to understanding Yellowstone.   I 
> thought
> people here would know that.   On my web site I also have links to 
> some new
> technical papers that ought to include that information.
>
> Yours,
> Dora Smith
> Austin, TX
> tiggernut24 at yahoo.com
>
>
> -- 
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