Robert B. Smith
NPR/NGS Radio Expeditions
19 Jul 1998
- Jackson; Bob Smith's house
- 43.47528 -110.76917
Stereo=1; Decoded MS stereo
NPR/NGS RADIO EXPEDITIONS
Yellowstone DAT #5
BS = Robert B. Smith
AC = Alex Chadwick
MS = Michael Schweppe
these are some mathematical models of how we let the n American plate move across ... \.
ac and bs talking
bob smith, prof of physics, U of Utah.
name of book?
"wind of honors?", geology of the Yellowstone teton system. and its not a conventional bk...relates more to the processes that are happening and how things form. doesn't have boring maps in it...point I'm making is that Yellowstone is a lie, you know in one of my careers I can see things change ...
and so the whole plate that Yellowstone is on it went up?
yes, they went up bc of the hot spot this little feature I'm talking about is kind of a little pimple sitting goes up and down that's the Yellowstone plateau that's where the magma finally leaks through to the surface and creates shallow magma systems so there's (paper rustling) a series of shallow magma systems that are clear at a depth maybe ten km. but the real source of it is clear down over here
just how would you describe Yellowstone in terms of how unusual a place it is in the world and in your area
well its the biggest sys in the world but the geysers are just the final product of the amt of heat coming through and the amt of heat that drives Yellowstone is about 30 to 40 times the average continental heat flux and that heat is what's driving, heat comes from a combo of magma and you see nothing in this scale anywhere in the world, now the comparable features are HI and Iceland in terms of geographic area, Yellowstone has a cauldron? of 75 km wide and ____ is what 2-3 km wide? but this s a diff system you are cooking a cont plate whereas hi and Iceland are on oceanic plates and they're very thin and they're very clean this plate's been around for 2.8 billion yrs so you're having to bum the candle through rocks that are 2.8 bill yrs own whereas in the pacific you're burning rocks that are 20 million yrs old. 6:06
you talk about this magma which is a pool of molten rock, a very hot place
well people like to think that magma are chambers where you can take you're boat down in to row around and that isn't true , they're like a sponge in the magma only obtains maybe ten-twenty % of total volume so its like a sponge where the sponge mat would be the hard rock and intermixed with pores would be magma but the magma are 1200 degrees (centigrade)
well why is it that's happening under Yellowstone that's not happening under anywhere else in the country and indeed the world?
well you've got magma that's coming up from a source in the upper mantle which we call a hotspot.. .that originates at depths of fifty miles and goes down maybe 200 miles and so there is magma coming out in partial melt form and in the crust that is a depth of maybe 5-8 miles then you create smaller chambers of this magma ... and then every once in a while it burps through and creates these gigantic eruptions and the last one was 600,000 yrs ago ... released 100 cubic km of material came out of the ground, these are catastrophic explosions they sent material in the atmosphere prob circle the globe for tens of yrs covered 20 of the western states with ash so the amt of energy going into these things is enormous, we've never seen this type of what we call rhyolitic eruptions in historic time, y. had one at 630, 000 there was one at west side of y. at 1.2 million yrs ago, then the initial one at y was 2 million yrs ago. that released 2500 cubic km so it was a lot of energy coming through, so we're driving energy into the earth's crust by the uplift over the hotspot.. .creates tremendous earthquakes, we've had the largest earthquake interior of western us in historic time ... day to day size vi city in y prob highest in most of the rocky mts when it gets turned on in swarms of earthquakes and so we have a tremendous amt of re activity, we have uplift, ess the calder is going up and down I mean I coined the term many yrs ago the idea is that the calder we know has risen for at least 50 yrs or more and now its going back dwn and the long-term record is that it prob goes up and down with the intrusion of magma into the crust and ev once in awhile it releases a few of these gigantic eruptions about ev 600,000 yrs or in between it releases smaller eruptions, if you took the total volume of all of y eruptions the gig eruptions and the smaller err and they're the size of mt st helen's and pinotubos, you'd have enough volume to fill the grand canyon more than once, I think I calculated if you took all the ash out of (better not quote me on this) and but it on top of WDC it would be n miles thick, that's a good way to quiet things down.
talks about ash covering area
at any rate its a gig energy ctr of both heat uplift and earthquakes interrupted periodically by volcanoes but it is a volcano ...
ac y-is a volcano?
yeah, its a volcanic system its so big you can't see it, its like the old indian farmer whose blind and he walks up to the elephant and touches the skin and he doesn't quite know what it is its so big I mean the y plateau is hundred km or so wide that's how big the uplift...
why is it there is any place on earth that's like this?
there's magma close to the surface in many volcanoes that's not unusual...the real? is why is y event there
we do have other hotspots in the world ... these are all ctrs of hotspots but they're all oceanic and you can explain them bc they're plate boundaries that are spreading apart we're sitting in the middle of a plate and so the? how did it get here? it got here we think,
best evidence is that it began 15-17 million yrs ago when magma came up to the surface somewhere southeast of boise idaho, and we think that it started there ...
its actually widening ...so you have the widening that's just like opening this brittle plate and the very in the direction that's easiest for the magma to come up ... there's this source
of heat at a depth of 200 miles creating partial melt the basalts come up ... so it melts before salt comes in,
(talks about creation of rhyolites and basalts)
and so what you have left.. . are the basalts that are black which ... which are rhyolites that are pink and orange and purple. eventually they're going to fill in so we always say, eventually they're going to have ... ?(can't understand) ...
what is going to happen to y?
there's 2-3 ideas, there's the idea that this progression up the snake river plane, which the plates roughly at an inch per yr...is ess an inch a yr, so one thought is that if ev is going constant, then ev you'll be burning new volcanics through the mts to the northeast of y, and you'll have new y out there. however, we've been looking ... composition ... beginning to show well first of all the rate of eruptions beginning from 17 million yrs ago when y started is really decreasing so the end result, you can have rates ev 600,000 yrs filled in w smaller ones. my thoughts are that in the long-term we are going to have some form of vulcanism
talks about frequency of eruptions
so thes things are not like clockwork. ..not periodic but there is also the matter of the big eruption ...
and the real question is are we currently in the tail end of that eruption or are we in the beginning stage of a new eruption--we don't know there's no way to know that, we're just beginning to understand how ev fits together, not just vulcanology ....
and the only thing I can really say is that if another big eruption were to happen we have in place a net of seismographs, putting a modem sys of gps ... but I cannot predict and I don't think anyone else can where we are in the cycle of catastrophic eruptions ...
we've come here to do story on fires, heat...heat that's coming ...
one thing is you've mentioned fire and animals one of the things i've come to view y as an ecosystem, somewhat unique I just presented a bunch of info biologists really brought onto it...whole y plateau several ft higher than surrounding ... these things all interact with geology and so angain my pitch is the geo-ecosystem...
at some point destroyed by volcanic and earthquakes
well prob both going to continuing mag, earthquakes ...there are five major fault zones within the plateau. (names them) ... these faults are just releasing energy ... cause faults to be loaded so that creates the earthquakes ...
we did work w Jason project...
are there earthquakes underway now in y?
oh yea we get, right now we get 2-3 a day on magnitude of 1-2 variety they're not large ... we've had earthquakes historically as big as 7.5, for every 7.5 there's 10 6's and a hundred 5's and a thousand 4's and uh so eq are a common occurrence, we sometimes get eq occurring in swarms, swarms is a set of eq that has a large number of events, but these eq can sometimes occur ...
bs talking about hotspot creating glacial features
if you had to guess how long do you think y will persist today?
but these are all guesses they're estimates, we can't make those calculations cause no one's ever studied a system like this there's no hotspot on a continent, all the hotspots are in oceans except Yellowstone ...
caldera is now sinking?
caldera has been sinking since 85
how far down can it go
well it went up a meter between 23 and 85 so it could go back down one meter ...
airplane in background, low humm
bob smith's house
talking in back, wind, fly buzzing, birds
wind very strong @33:30 to 33:53.