Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Don_1 on 29/10/2008 08:57:36
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You Americans really should consider yourselves lucky. The North American continent has had some natural geological phenomena which has left some spectacular and beautiful landscapes. The Rocky Mountains, The Colorado River, The Grand Canyon (to name but a few) and this scene, which Bass posted in ‘Where in the World?’
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.thenakedscientists.com%2Fforum%2Findex.php%3Faction%3Ddlattach%3Btopic%3D7772.0%3Battach%3D4554%3Bimage&hash=3cf09a57713af61efec004ad670d7986)
which Bass revealed as being
Earthquake Lake along the Madison River in Montana, just west of Yellowstone Park.
Seeing this beautiful scene, however, has prompted me to pose the inevitable question about Yellowstone Park.
Geologists had been looking in the vicinity of Yellowstone Park for a volcano for some considerable time. They knew there was one there, but were unable to find it until the US Air Force got high-flying spy planes. It was only then that geologists discovered that the reason they had been unable to locate the volcano was because they had been looking over far too small an area. Pictures taken by a spy plane revealed that practically the whole of the park was the creator of a super volcano.
It has been suggested that the evidence points to this super volcano having erupted at 600,000 year intervals in the past and it is roughly 623,000 years since the last eruption.
‘Old Faithful’ continues to live up to it’s name, which might suggest that the volcano is, for the time being at least, stable. But is it? Does anyone really know the current state of the Yellowstone Park super volcano?
What would happen if it were to erupt in the next few years? Would the consequences be far too dire to be imagined? Would it cause a mass extinction which would render the planet uninhabitable for the human race?
Doomed, doomed I tell you, we’re all doomed! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fscared003.gif&hash=3f82a39ee46b7861d52ddf0303228d75) (http://www.freesmileys.org)
[MOD EDIT - Don_1 please structure your post thread titles as questions, in line with our forum format.]
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Opps, sorry Chris.
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From another thread:
There have been three VEI8 (Volcanic Explosivity Index [level] 8) eruptions at Yellowstone, the first being 2,100,000 years ago, the second being 1,300,000 years ago and the most recent being 640,000 years ago. While the average interval between them works out to be about 730,000 years this is only taken from two samples, of intervals of 800,000 years and 660,000 years - hardly a good basis for making an accurate estimate.
That the Yellowstone system is still very much active is beyond doubt, and it is entirely possible that another VEI8 eruption might occur there, but as to when, if ever, it will occur is completely open to debate. For example if, instead of comparing the average interval with the most recent recent interval, we go by the interval between the first and second eruptions, then far from being overdue another VEI8 eruption we've still got another 70,000 years to wait.
What is much more likely, and even probable, is that a minor eruption will occur 'soon' - perhaps even sometime in the next few thousand years. Such an event would be entirely in keeping with the known behaviour of the Yellowstone system, which has had many more smaller eruptions than the large VEI8 ones, the most recent being about 70,000 years ago.
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Wouldn't the destruction of the Yellowstone Park in the Rocky Mountains possibly start off another volcano in the Mt. St. Helens as happened in the early 1980s?
Unless I have my geography all over the place. That's possible.
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The eruption at Mt. St. Helens didn't end with the 1980 event and the volcano continued to be active until around February this year (2008), building quite an impressive lava dome in the process.
It's unlikely that an eruption at Yellowstone, regardless of it's size, would have any effect at Mt. St. Helens. The Cascades volcanos, of which Mt. St. Helens is one of the smaller examples, are driven by the subduction of the northern pacific plate under the north American plate, whereas Yellowstone seems to be currently sitting over a 'hot spot' - one of the hypothesised mantle plumes, similar to the one that made the Hawaiian islands. They're driven by different systems.
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I would normally let Bass answer this since he practically lives in Yellowstone and is a compendium off erudition about this subject. But since Bass is playing Paul Bunyan this week - he has delusions, you know - it seems that I should address this subject with the knowledge available in my own complete compendium of Geologic Knowledge. (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.emotihost.com%2Fglass%2F6.gif&hash=f74212076fdbc104c1047cece9fbd527)
Lee is correct - it is a mantle plume. But the evidence for the hot spot goes back a LOOOOOONG time. 100 Million years at least. Unlike the Hawaiian Islands, which are formed from basaltic lava, the Yellowstone hot spot has rhyolitic lava. This is because the lava is formed by the remelting of the continental crust, which has a lot more silica in it than the crust below the oceans have. The Hawaiian volcanoes are probably a result of remelting of oceanic crust and the material of the hot spot plume itself.
The map below shows the trail the hot spot as the continent has moved over the hot spot. I have put my own labels on the map to help you see eruption points (calderas) and the resulting the trail of eruptions.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FYellowstoneMapAnno.jpg&hash=9737feae5a23f1348fdb300da82e8924)
Because the older rhyolites are small and mostly covered by newer basaltic eruptions it is difficult to find the caldera from 70 Million Years ago.
For a complete education on the Yellowstone area see a joint US Geological Survey and Durham University collaboration resulting in a paper linked below, in the Geological Society of America. It can be found at: http://www.dur.ac.uk/g.r.foulger/Offprints/Yellowstone.pdf If you go to this link you will see a bigger map.
"Thank you, thank you very much" - Elvis
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Oh, it wouldn't cause mass extinctions and such. It would cause a loss of the amount of radiation from the sun as the ash would remain in the atmosphere for years. And humans would survive - in the southern hemisphere for sure and probably in the northern as well. The eruption would just totally mess up the whole US west of the Mississippi River.
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Thanks for the clarification on lava types between the two plumes.
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Wouldn't the destruction of the Yellowstone Park in the Rocky Mountains possibly start off another volcano in the Mt. St. Helens as happened in the early 1980s?
Unless I have my geography all over the place. That's possible.
Rosalind, there is no connection between the two volcanoes. The two are over 560 miles apart and the forces that drive them are different in origin. Mt. St. Helens is caused by melting of the oceanic and continental mantle due to subduction of the Pacific Tectonic Plate. The Yellowstone Volcano is due to a hotspot, an upwelling of the material that forms the inner mantle of the earth. This then melts the already existing outer continental crust which, because it has water in it, forms a more explosive type of volcano, but only slightly more so than the subduction volcanoes like Mt. St. Helens.
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Not to mention that even IF Mt St Helens, Mt Shasta, Mt Hood, Mt Ranier, and the rest of the Cascade Range volcanoes were to erupt as well, it would be like firing BB guns while firing a howitzer.
I know you and I have had conversations about this, JimBob, but I still cant shake the feeling that the N. American plate overriding the area where the two divergent mantle convection cells that formed the edges of the Farallon and Pacific plates, in addition to the mantle plume, has something to do with the Yellowstone volcano. I cant claim much technical knowledge of the subject...it is merely conjecture.
The plume would have to punch through two plates (the Juan de Fuca and N. American) to reach the surface. It would seem (in a wholly unlearned view) that the two plates would form some kind of magma trap between them. I know that the Farallon has very shallow subduction in the SW US, but Im not sure the same holds true in the NW.
Oh, and...HOOK 'EM HORNS!
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No, No, NO, Grasshopper
The Juan de Fuca is what forms the present Ring of Fire, forming the Cascades and the coastal ranges in California. The Farralon Plate is what forms the Colorado Plateau area. It went to the southwest - relatively speaking. The Yellowstone hotspot is a mantle plume that has been in relatively the same spot as it is today. Plates have moved over them.
See http://www.geology.wisc.edu/courses/g112/mtns_westernUS.html for a complete explanation.
I am very glad all these professors has put their lectures on-line. Saves Bass and I from finding all the illustrations and writing all the explanations!
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But the Juan de Fuca, Rivera, and Cocos plates are all modern remnants of the Farallon plate. I undertand that the hotspot has remained still and that the plates have moved over them, but at around 5-10 Ma, the Farallon shifted from deeper to shallow subduction (creating the Colorado Plateau) in the SW, which would seem to indicate that the Farallon is still in process of subduction, as the Plateau has not yet begun to subside. Since the Juan de Fuca and Farallon were/are one plate, would an uplift in the SW cause some sort of shallowing in the NW? From a laymans point of view, being so close to the actual mantle convection cells would seem to inhibit a deeper subduction because the force from the convection might push up on the plate edges.
I am wondering what the implications of this might be for the Yellowstone hotspot, because at this point it would have to punch through two plates simultaneously. Does it change the magma chemistry to something more felsic? Does the space between the two plates affect the dimensions of the magma chamber? If the magma chemistry is changed, how does this affect the explosiveness of the eruption?
BTW...I bookmarked the lecture you gave...great info!
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You need to be introduced to the Texas Lineament, that wonderful, just now being recognized lineation of continental movement that is a strike-slip zone running from the Rio Grande Embayment on the south east through Texas, New Mexico, Arizona, Nevada (Walker Lane Fault Zone) and possibly separating the cascades from the Coastal Ranges in California. The Western extension of it can be seen rather clearly on the Early-Mid Miocene and late Miocene maps in the link provided above.
The big deal is that the WESTERN part of the Farallon plate has become separated and spewed out as volcanincs and perhaps emplaced (with continental crust) even as granites due to the extensional tectonics that formed the Basin and Range province of North America. So there really is no subducting plate near Yellowstone.
Dang it. As this link my not be up forever I need to put them on my Photobucket pages - I'll annotate them as well. - Next post.
In the meantime you will be by for your tutorial so we shall discuss this in a depth not subtitle for any others but us geo-geeks.
You will keep a transcript for posting, I hope.
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The map
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fi38.photobucket.com%2Falbums%2Fe111%2Fgeezer69%2FWUSpalgeo_5Ma.jpg&hash=e96677ad8491bfabe130976f4cb6fd98)
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Does this mean no more Boo Boo ?
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Yabba dabba doo, Oh sorry, wrong cartoon!
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Does this mean no more Boo Boo ?
Nooooooo that means.. no more Karen W......i am right on that line at the top of that little nub..... I sit right on it... every day all day.... not a good place to be...although itis quite lovely here!
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Makes me nervous when JimBob makes these "off-the-cuff" remarks- mostly because I have to "cuff" him for being "off" (but then again, we've known for quite some time that JimBob is off)
I would normally let Bass answer this since he practically lives in Yellowstone and is a compendium off erudition about this subject. But since Bass is playing Paul Bunyan this week - he has delusions, you know - it seems that I should address this subject with the knowledge available in my own complete compendium of Geologic Knowledge.
(Hmmm- sort of like saying that visible light represents the complete compendium of the electromagnetic spectrum) [???]
Forgive this long post, but there is soooo much to comment on...
Lee is correct - it is a mantle plume.
Maybe. According to the article that JimBob posted, the jury is still out as to whether or not the Yellowstone hotspot is a deep mantle plume, or is a localized shallow mantle heat anomaly caused by crustal extension and thinning of the continental crust.
Personally, I agree with JimBob on this one- my vote is for deeper mantle convection.
But the evidence for the hot spot goes back a LOOOOOONG time. 100 Million years at least.
Oh, great but ancient JimBob, though you were but a mere teenager 100 million years ago, perhaps you should check your memory pills??? The McDermitt Caldera along the Nevada-Oregon border, dated 16-17 million years ago is considered to be the first appearance of the Yellowstone system. From McDermitt, there are two time-progressive volcanic tracks: to the northeast ending at Yellowstone park and the other to the northwest ending at Newberry Caldera.
Unlike the Hawaiian Islands, which are formed from basaltic lava, the Yellowstone hot spot has rhyolitic lava. This is because the lava is formed by the remelting of the continental crust, which has a lot more silica in it than the crust below the oceans have. The Hawaiian volcanoes are probably a result of remelting of oceanic crust and the material of the hot spot plume itself.
Mostly correct. While Hawaii is entirely basalt, the Yellowstone system is bimodal- composed of rhyolite and basalt. Hotspots originate in the mantle, which is made of material similar to basalt. Hawaii is basalt-only, because this mantle material can erupt easily through the thin oceanic (basaltic) crust. In Yellowstone, the rising melted mantle (basalt) heats and melts the lighter, thicker, more silicic continental crust, forming rhyolite. It is the rhyolite magmas that explode so catastrophically. As the hotspot moves to the northeast (actually the continent moves to the southwest), old eruptive sites cool down and shrink, allowing the unerlying mantle material to erupt as basalt. Most of the old calderas, now the Snake River Plain, are completely covered by basalt. Volumetrically, there is more basalt than rhyolite in the Yellowstone system, especially if you count the Coulumbia River Basalts which erupted at the emergence of the hotspot and the initiation of crustal extension in the Basin and Range.
The map below shows the trail the hot spot as the continent has moved over the hot spot.
Revised map (dark oval is McDermitt Caldera where Yellostone originated 17 million years ago, with arrows showing time-progressive tracks of calderas to the northeast and northwest):
SEE MAP BELOW
Because the older rhyolites are small and mostly covered by newer basaltic eruptions it is difficult to find the caldera from 70 Million Years ago.
Might also be because the Yellowstone System is only 17 million years old.
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It has been suggested that the evidence points to this super volcano having erupted at 600,000 year intervals in the past and it is roughly 623,000 years since the last eruption.
‘Old Faithful’ continues to live up to it’s name, which might suggest that the volcano is, for the time being at least, stable. But is it? Does anyone really know the current state of the Yellowstone Park super volcano?
What would happen if it were to erupt in the next few years? Would the consequences be far too dire to be imagined? Would it cause a mass extinction which would render the planet uninhabitable for the human race?
Doomed, doomed I tell you, we’re all doomed!
I have to agree with the other posts on this thread (even JimBob, much as it pains me). There is no threat of imminent eruption of the Yellowstone volcano. All sorts of precursors should be active for some time before an eruption- thankfully, none of the volcanic indicators hint that any sort of eruption will occur in the near future.
Will Yellowstone erupt again? Absolutely. But even living only a few hundred miles away- I still have no trouble sleeping every night.
A large caldera eruption would be devastating. Much of US agriculture would be under several inches to feet of ash and may not recover for several years. World temperatures will plummet, most severely in the northern hemisphere.
On the bright side- sunsets will be spectacular for probably several generations.
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Frethack- your question is more intriguing- I'll address in more detail in the near future.
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Revised the map in my earlier post, hopefully more easily seen:
Oval is McDermitt Caldera, arrows show both the northeast and northwest time-progressive series of calderas. Extensional tectonics (crust is pulled apart), known as the Great Basin or Basin and Range province, extends from the tip of the northwest arrow to the tip of the northeast arrow.
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If it happens that Yellowstone is caused exclusively by a deep mantle plume, could this same plume be the progenitor for some of the exotic terranes accreted in the northern cordillera region over the past 100my or so? Sorry bout all the questions (My knowledge on the subject is a bit sparse).
Thanks for the reply...and welcome back Bass :)
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The plume would have to punch through two plates (the Juan de Fuca and N. American) to reach the surface. It would seem (in a wholly unlearned view) that the two plates would form some kind of magma trap between them. I know that the Farallon has very shallow subduction in the SW US, but I'm not sure the same holds true in the NW.
Frethack, your "unlearned" view is held by several earth scientists and is still the subject of controversial discussions on the tectonic history of the Pacific Northwest and the Yellowstone hotspot. No doubt that the "Jaun de Fuca" plate (remnant of the Farallon plate) was being subducted beneath central Oregon when the Yellowstone Hotspot first erupted around 17 million years ago. Which means, as you so succinctly stated, "The plume would have to punch through two plates..." to reach the surface.
So how did that affect the hotspot and volcanism in the NW? How did it affect the descending Jaun de Fuca slab? What was the effect on extensional tectonics in the western US? Why does the hotspot appear to be propagating in two different directions from its original appearance in McDermitt Caldera?
Richard Allen (Berkeley) has an interesting take on this- check out this recent article http://seismo.berkeley.edu/~rallen/pub/2007xue/XueAllenEPSL2007.pdf
His theory is that a mantle plume punched through the two plates, effectively destroying the older part of the Juan de Fuca slab in eastern Oregon (though this slab is still evident further north in British Columbia).
Several geoscientists have speculated that hotspot material ponding beneath the Juan de Fuca slab may have been responsible for massive Columbia River Basalt/Steens Basalt provinces. It is interesting that their eruption is very close in time to the appearance of the Yellowstone Hotspot.
Others suggest that the hotspot already existed, possibly over 120 million years ago, in the Farallon plate- and that the hotspot was subducted beneath the thick western edge of the North American plate only to re-emerge in the thinner crust of central Oregon. As you suggested, this could account for some of the exotic terrains of northern CA and southern OR.
Still others question whether extensional tectonics might have caused "slab shear", that resulted in a shallow, upper mantle heating anomaly that we call the Yellowstone hotspot? In other words, did extensional tectonics cause Yellowstone, or did Yellowstone cause much of the extensional tectonics?
Your "unlearned" observations are apparently right on.
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Thanks for the article! Any other suggested articles would be greatly appreciated. I should be studying carbonates right now (test tomorrow!) but mantle plumes and plate tectonics are a nice distraction [;D] Even after Im done with this one, I still have the references section to go through!
You may have created a monster, Bass.
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OK, jerks - I mean guys - including the (betrayal) of the "geologist" cum forester.
What you guys are not privy to and what might change your mind, if we did not have an oil and gas prospect in involving the data, (it is for sale anyone!) is that there is evidence covered up by subsequent deposition and basaltic flow of another, larger, much older caldera in the subsurface, southwest of the one you have defined, Bass.
This is beneath the Modoc Plateau. Magnetotelluric data we - my partner and I - have gathered, collated, related to well bore data and interpreted suggests a very large eruptive caldera beneath the basalt terrain and the subsequently slightly deformed sediments.
I present an edited version of Ernie's publications on MT - He and Arnie, our former partner, literally invented the application of MT to geology - first paper in 1981. There is also a tripple junction involved here - that of a rift valley, a subduction zone and a line of volcanoes. Seems like things seen in other areas of the globe where such junctions occur, mainly under the sea.
OK, More to follow. I have finally caught up with much of the work I have on the plate. There is more yet to do. So more on this matter will need wait.
Berkman, E., Orange, A.S., and Wach, P.H., 1981, " An Integrated Approach to Volcanic Covered Prospects", Society of Exploration Geophysicists, 51st Annual Convention.
Berkman. E., Goss, R.D., Orange, A.S., and Smith, R.D., 1981, "Adaptive Magnetotelluric Exploration Utilizing In-Field Processing", Society of Exploration Geophysicists, 51st Annual Convention.
Berkman, E., Orange, A.S., and Smith, R.D., 1983, "Seismic and Magnetotellurics Combined, A Case History of the South Clay Basin Prospect", Society of Exploration Geophysicists, 53rd Annual Convention.
Berkman, E., and Orange, A.S., 1984, "Interpretation of Magnetotelluric Data, Pasco Basin, South Central Washington", United States Department of Energy, SD-BWI-TI-233, 174 p., 61 figures, 3 tables, 16 plates.
Berkman, E., and Orange, A.S., 1985, "Interesting Aspects of Magnetotelluric Data in Northwestern Montana", Society of Exploration Geophysicists, 55th Annual Convention.
Prieto, C., Perkins, C., and Berkman, E., 1985, "Columbia River Basalt Plateau - An integrated approach to interpretation in basalt-covered areas", Geophysics, v. 50, no. 12, p. 2709-2719, 13 figures, 1 table.
Berkman, E., Orange, A.S., Bergstrom, K., and Mitchel, E., 1987, "Interpretation of Magnetotelluric Data from Rattlesnake Mountain, Pasco Basin, South Central Washington", United States Department of Energy, SD-BWI-TI-354, 31 p., 7 figures.
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TIMBER!!!
(Run for your lives) [::)]
Correct me if I'm wrong, but wasn't the buried caldera in the Modoc Plateau dated around 10 to 12 million years?
Basalts are Pliocene, if my memory hasn't completely failed me- which means they are more correlative to Snake River Plain basalts than to Columbia River basalts.
Either way, bimodal volcanism reeks of extensional tectonics. Will get around to reading articles you cited when time allows.
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Nope, the Modoc Caldera is older - early Miocene for both the basal basalts (hi resistivity zones) and the sediments - according to the bugs from the sediments interbedded with basalts... It fits well with the age of the Yellowstone hotspot...
And YES - extensional tectonics - it REEKS of this!
I was about to chastise you on how WRONG you are in implying such a small basin and range - placing such a limited area as the area of the Basin and Range just between the two arrows. This is just the northern limit of the Basin and Range. The Basin and Range extends all the way into northern Mexico! Parallel ridges in Arizona, Walker Lane Fault Zone, all of Nevada.. all of this is the modern expression of the extensional tectonic zone. It is everything from the Colorado Plateau to the Coastal ranges of California. The San Joaquin Valley is extensional tectonics. and on the east the Rio Grande Rift is extensional Tectonics. It is a HUGE area!
The articles were just to sell our company's consulting business but do have scientific value.
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I was about to chastise you on how WRONG you are in implying such a small basin and range - placing such a limited area as the area of the Basin and Range just between the two arrows. This is just the northern limit of the Basin and Range. The Basin and Range extends all the way into northern Mexico! Parallel ridges in Arizona, Walker Lane Fault Zone, all of Nevada.. all of this is the modern expression of the extensional tectonic zone. It is everything from the Colorado Plateau to the Coastal ranges of California. The San Joaquin Valley is extensional tectonics. and on the east the Rio Grande Rift is extensional Tectonics. It is a HUGE area!
psst- JimBob, I was trying to keep the map simple enough for even you to understand. But rest assured that I would never question your capabilities on the forum
Interesting recent article on Modoc basalts...
http://www.geol.ucsb.edu/faculty/busby/Manuscript_pdfs/Garrison_et_al_2008.pdf
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Dang nabit! Knew we should have published or done a poster session on it 20 years ago!!!! Now there is proof!
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Please, I'm OK, I was just overcome there for a second. Thank you for the brandy, butler.
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how long after an eruption there would I have here in PA ? Basically if it erupted tomorrow at 8 am would I have til 3 to get on a plane and go or???
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Ash would travel no faster than the winds/weather aloft, so I'm guessing 18 to 24 hours?? But I wouldn't make your reservations just yet.