Eruptions

Yep I knew it would be on the air one of these days but haven't yet seen the bit (waiting for Discovery to send me the DVD). It's about the big sector collapse on Etna's eastern side about 8000 years ago - that was indeed something we would not want to see today, and it might have lesser global impact than a new caldera-forming eruption at Yellowstone but it would hit much more densely populated areas. It was like the collapse of Mount St. Helens in 1980 but about 10 times bigger, and the debris avalanche went into the Ionian Sea, producing a massive tsunami.
Guess what, nobody is worried about a repetition here - although we're seeing signficant displacements on Etna's eastern flank, which have accelerated since 2002. But after all, the sector collapse is once more a worst-case scenario and therefore the least likely to happen. And something similar is happening - at a much grander scale - at Kilauea, and it seems that these basaltic volcanoes have a capacity of "buffering" such flank instability induced mass movements much more efficiently than stratovolcanoes such as Mount St. Helens, Augustine, and an incredible number of further volcanoes that have undergone (and will again undergo) catastrophic sector collapse.
Fun though that both of us - Dr. Erik Klemetti and I - have been through the Discovery publicity machine these days. By the way, the article that Randall Nix refers to in comment #31 in the caldera post (http://scienceblogs.com/eruptions/2010/02/the_structure_of_calderas.php) is not so bad after all - most of all because differently from some of the news media, it says the right thing. There is no serious concern about Yellowstone for the moment; a volcano that's going to "super"-erupt soon would look and behave VERY differently, of that we can be sure. But that would be the matter for another comment, once the burden of apocalypse obsessed once more goes beyond a certain threshold.

Posted by: Boris Behncke | February 5, 2010 8:58 AM

Boris I am sorry I know you are the expert but are you saying you agree with the guy who wrote the Discovery News story.....do you really think an eruption at Yellowstone might be cool and that if we are lucky we might get to see one just to shut "people" like me up? I quote from the story:

"A dome eruption (kind of like toothpaste squeezing out of the planet more than an "eruption" like you might picture it) would be cool in that it would add to Yellowstone's unique, ever-changing landscape.

If we're lucky, it might even convince some of the people waiting for the end of days to come roaring forth from Yellowstone Caldera that they're wasting their time."
Sorry but I couldn't get this to post with the link to the Discovery News story but those are quotes from it.

According to the paper I posted on the site yesterday:
Mushy magma beneath Yellowstone caltech.edu [PDF]
R Chu, DV Helmberger, D Sun, JM … - Geophys. Res. …, 2010 - mh-gps-p1.caltech.edu
HTML Version
http://74.125.155.132/scholar?q=cache:Y9JjMTR4_tsJ:scholar.google.com/+yellowstone+caldera&hl=en&as_sdt=40000&as_ylo=2009
PDF Version
http://mh-gps-p1.caltech.edu/~jackson/pdf/Chu_2009GL041656.pdf
The previous measurements of the magma chamber were not correct. The magma chamber was found to be 4300km3 in volume and more importantly with 32% melt saturated with 8% water plus CO2 by volume. In other words the magma chamber has much more of an explosive potential than was previously thought. Like I said you are the expert so if I am reading this paper wrong please enlighten me.

I took this from the YVO site:
"One way to think about a magma chamber or magma body is to picture a water-filled sponge. The sponge would represent the solid rock whereas the water would represent the melt. Beneath Yellowstone, on average, the magma is about 90% solid rock (like a hot sponge) containing 10% liquid rock in its pores. "

"scientists estimate that the melt part could be about 10% of the low velocity volume or about 1,500-2,000 cubic km."

The YVO better start looking at this thing a little differently in light of the most recent mesurments. Even if this swarm stops there is still a BIG reason to more concerned than we were before this study was published.

Posted by: Randall Nix | February 5, 2010 11:33 AM

I am posting this here because we are getting quite a few down the pike.

@Shannon: You are very welcome. I don't want you to be afraid of Yellowstone. The more you come to this site, the more you will learn and maybe the volcanoes will become something of real interest to you. I have been intrigued by them since I was at least in the third grade! I used to draw them. Anywya, hang in there keep learning.

@Rick: I don't think the quakes and uplift at Sisters has anything to do with Yellowstone. They are different systems. Yellowstone is a hot spot. Sisters and the whole Cascades are from subduction, I think, if I remember right, of the San Juan De Fucca plate under the Pacific Plate. Also because of the Pacific Plate being up against the North American plate. The North American plate moves westward and the Pacific plat moves roughly NNW. That is what gives us the San Andreas fault in CA. I hope this helps. Any of you volcanologists out there can correct me if I have some of this incorrect.

Posted by: Diane | February 5, 2010 12:30 PM

Dear Randall, certainly the Discovery News guy doesn't think a huge Yellowstone eruption would be anything similar to "cool". But a lava dome eruption would be of extremely limited extent - the more so because Yellowstone is a National Park, differently from our Italian "supervolcano" Campi Flegrei, which has half of Naples in it, and which might well erupt long before Yellowstone.

To be honest, what is going on at Yellowstone is not new, that's the first thing you must come to terms with. It's the totally normal business for a volcano of its kind. The article in Journal of Geophysical Research says simply that there is presumably (not certainly) a quite impressive quantity of semi-molten rock present below Yellowstone, but it doesn't say with a single word that it will erupt soon, just that it is potentially explosive. Duh, what a surprise. But can you imagine how many volcanic systems there are on this planet that are sitting on similar quantities of magma? Just take Etna, the volcano that is just some 10 miles away from my home, which sits atop a huge magma storage area estimated to host some 1600 cubic kilometers of molten rock. But even at a volcano as active and productive as Etna, which furthermore is basaltic (that is, its magma moves much more easily than Yellowstone's), only very small quantities of this magma reach the surface, and much of the remainder is doomed to sit down there and cool and crystallize.

Problem is, some of you folks focus entirely on that one thing, that one volcano, that one scenario, but it would be rather smart to realize that among all the bad stuff waiting to fall upon us this is probably the least likely to happen of all, and those things more likely to happen should rather frighten the hell out of me with our nasty Italian volcanoes here, and - ... well, I am not frightened about the Italian volcanoes, I am very concerned, and I am working with the people here to educate them to be prepared and understand what the risks are. I can assure you that there are lots of people here who show the same type of reasoning that you do, they pick what sounds adequate to confirm their worries and anxieties, but don't look at the rest of the picture.

Personally, I am worried of being run over by a car (not too bad prospects in Sicily) or by debris falling off one of the many relatively modern but badly constructed buildings in Catania - they crumble even without an earthquake occurring - or of dying painfully from cancer. I fear any one of these or something equally evil is about ten million times more likely to happen than a "supervolcano" eruption at Yellowstone or anywhere else.

What is important is, once more, that you understand that the YVO people and our other colleagues worldwide really know their business, they're not there because they've read one scientific publication and watched a few Discovery and National Geographic and BBC supervolcano specials (I don't mean that this applies to you specifically Randall, but it certainly does to a great number of people, including many self-proclaimed experts). We've undergone a long education to get our know-how, and luckily technological evolution in the past few decades has been enormously helpful. And yes, quite a few of us do risk our lives every now and then during our attempts of understanding volcanoes better.
Just believe me, if Yellowstone were up to something big, it would be EXTREMELY evident. We can be certain of this even though no one of us has ever witnessed a "super" eruption, because in the end, the underlying processes are the same that operate in small volcanic events as in large. If we can detect the uprise of 0.005 cubic kilometers of magma weeks in advance at Etna, then I would say with all the monitoring equipment that sits on Yellowstone a much larger quantity of magma moving would hardly be able to go unnoticed.

@Diane, nice to be back in touch after all those years, and your contributions here are quite helpful and accurate - in a particular way because you're actually representing the public, not the expert view of things. It's only that you put them into a perspective of decades of being interested in things volcanic, tectonic, and geologic. I hope that this helps people who come in here and are worried but don't really understand what it's all about, having just seen "2010" or "Supervolcano" or the likes.

Posted by: Boris Behncke | February 5, 2010 12:46 PM

@Boris: Thank you for your comment. Expert, I am not, but I like to study this stuff and I did order one of the books Erik suggested. I have only had one geology course and it was back in the '70s! We had two teachers and one of them had a book that was all the seizmographs from all over the world of the 1906 SF earthquake. It was an original copy, too. Cool book.

The main reason we lost touch is I forgot to send you my new email addy before I changed it and I figured your spam filter might reject it. It is good to be back in touch!

@Randall: I am an avid rockhound and belong to a club called the Motherlode Goldhounds. We have fun. I am limited in where I can go and so is my DH. He was a miner and knows a lot about where to find stuff. I will write more later. I have a tree man here. Catch you later.

Posted by: Diane | February 5, 2010 1:23 PM

I understand what you are saying Erik and I do respect you because you are not condescending. I will have to say this though to Boris that I have never watched 2010, I don't believe in any of that stuff....Nostradamus is bull...Here is what I do believe....I believe 32% melt saturated with 8% water plus CO2 by volume verses 10% melt is quite a difference. I never said the paper said anything about how it's about to blow right now....The paper said the earlier measurements were way off...The paper said that there is a considerable difference in what was thought to be melt in earlier papers and what's on the on the YVO site. This means that there is a much bigger potential for an eruption. What percentage of melt do you need to reach before an eruption can theoretically occur? I do respect you Boris and I wish you would respect what I am saying and I wish you would just answer my questions without all of the reassuring analogies.

Posted by: Randall Nix | February 5, 2010 1:42 PM

@Randall, I'm not getting the point about the "reassuring analogies". I do respect what you are saying (and that's why I'm spending a bit of my time here responding), but I do not think that anybody should worry about Yellowstone in particular, and not worry about much more dangerous things. That's the first point. Second, if you believe that you have cancer and go to a doctor and he says no you don't, and maybe you go to see a whole bunch of doctors and they all say, no you don't have cancer, will you insist any longer or shouldn't you be rather happy that very obviously you don't have cancer?
I hope you understand that I am a very normal human being like you and I do have my own anxieties (I mentioned a few in the message before), which are based on real probabilities, unfortunately. But when it comes to volcanology I think I have my things together. So please do accept when I try to reassure you: there is not very much to worry about Yellowstone in this moment, not more than in 1985 when there was surely as much magma below the volcano as there is now, but nobody talked about it. And not more than a great number of other volcanoes, which threaten half a billion people worldwide. It is the analogies as you call it, or the comparisons, which make us understand the real significance of Yellowstone. It should make you understand that there is really nothing extremely frightening in the data about Yellowstone you refer to, fascinating as they are. As Erik Klemetti said before, things need to be put into perspective. Thinking about Yellowstone is worth nothing if you don't think about other volcanoes, other hazards, other threats to our lives.

Posted by: Boris Behncke | February 5, 2010 2:46 PM

Thank you for your response Boris and I do appreciate you trying to answer some of my questions. I would still like to know, if you happen to know just off hand.... If the magma chamber is 32% melt instead of the 10% reported in earlier papers and on the YVO site...then please let me and everyone else here know just what is the theoretical level of melt that has to be reached before an eruption can occur?

Thank you for your time and consideration of my questions. Thank you again Erik for providing us an opportunity to ask someone like Boris questions, to express our opinions as well as the concerns that I and others may have.

Posted by: Randall Nix | February 5, 2010 3:13 PM

Erik, You are wrong about one thing...I did like your answer;) I like getting direct answers. I can assure you that I will be very happy to never see an eruption at Yellowstone....I do have a few more questions and if it is OK with you I will be back to ask them at a later time. Thanks again!

Posted by: Randall Nix | February 5, 2010 4:53 PM

I took this except from:
Monitoring super-volcanoes: geophysical and geochemical signals at Yellowstone and other large caldera systems
Jacob B Lowenstern1,*, Robert B Smith2 and David P Hill1
+ Author Affiliations

1US Geological Survey, Volcano Hazards Team, MS 910 345 Middlefield Road, Menlo Park, CA 94025, USA
2Department of Geology and Geophysics, University of Utah 135 South, 1460 East, Room 702, Salt Lake City, UT 84112, USA
*Author for correspondence (jlwnstrn@usgs.gov)

"Overall, geophysical and geochemical evidence points strongly towards the presence of a large thermal anomaly in the shallow- to mid-crust. Given the size of the caldera and the implied depths, it is reasonable to infer that at least 15 000 km3 of crystal-melt mush are located beneath the Yellowstone caldera, at depths from ca 8 to 18 km. If melt fractions are 0.1–0.15, then sufficient melt exists to form the mass for a super-eruption—if it can be extracted and accumulated into an eruptible volume. Most geophysical images have insufficient resolution to define volumes less than ca 10 km on a side. It is fully plausible that volumes with high melt fractions (more than 0.6) exist within dikes and sills within the greater magma chamber, and could erupt as moderate-volume (less than 100 km3) lavas or pyroclastic flows. Current evidence suggests, however, that the gravity and seismic anomalies are not sufficiently large to allow for a larger, highly molten (and thereby eruptible) volume of magma beneath Yellowstone at this time."
http://rsta.royalsocietypublishing.org/content/364/1845/2055.full

Sorry Erik, please don't be angry with me but it seems like someone already has given us some hard numbers on what percentage of melt we would have to reach before the magma becomes and I quote "(and thereby eruptible)".

Posted by: Randall Nix | February 5, 2010 7:07 PM

Oh I didn't take it as any magmatic system with 10%-15% must erupt either...I think the number is higher than that. My point is that they do have an idea of how much melt that would have to be reached before a possible eruption. Also:

"Current evidence suggests, however, that the gravity and seismic anomalies are not sufficiently large to allow for a larger, highly molten (and thereby eruptible) volume of magma beneath Yellowstone at this time."

The paper I posted sort of conflicts with thier conclusion.

Posted by: Randall Nix | February 5, 2010 9:09 PM

The idea to have a bit on Laacher See here is not a bad one, because it's quite an interesting one, in a place where most people wouldn't imagine a major volcano (or a potentially active volcanic area), and source of a massive (though not "super") eruption about 13,000 years ago. There was a bit of a discussion about it already in September 2009 on this blog:
http://scienceblogs.com/eruptions/2009/09/monday_musings_more_australian.php
I passed much of my infancy and adolescence between Frankfurt and Cologne (Köln), not far from Laacher See and thus it was one of the first volcano I've ever visited in my life. It's a hauntingly beautiful place, all the Eifel volcanic field it belongs to is a sweet, lush green, hilly landscape with little historical towns and villages, lakes (many of them volcanic - they're called maars, and the term comes from there).
The Eifel volcanic field has recently been the subject of a German TV fiction last fall, depicting - very much "Supervolcano"-style - a Laacher-See-type eruption occurring today. While you can debate the quality of the acting and the storyboard as a whole, the movie came accompanied by a short documentary, which brought up a few sizzling questions: is it possible that there will be another volcanic eruption in Germany one day? (YES), and are the people, the authorities, and Civil Defence prepared? (NO).
However, as at Yellowstone and any other volcano, odds are that the next eruption will be a small to modest-sized cinder cone-building event, rather than a Laacher See size cataclysm.

Posted by: Boris Behncke | February 6, 2010 2:16 AM

@Sightseer: I wouldn't worry about the quakes in Yellowstone. Their magnitudes are not high enough to affect a motorcycle. Even a 3.8 could be navigated. The worst you would see would be like a dirt road. And I seriously doubt you will encounter anything like that.

Something happened to me that I though was rather humorous when years later I figured out what was going on. It was during the Loma Prieta quake. I had just left UPS and headed for Sac on I80 when the road felt kind of rough and I could see a ripple in the road that made it look like a washboard. Near where I live, they were working on the road and I was thinking they needed to fix this part of the road, too. Well, I got to where I was going and they announced on the radio about the quake. It made the water slosh in my parents' pool! I didn't think anything about it after that until years later when I decided to see if that part of I80 did need fixing. It was rather smooth with no washboard look to it at all. That is when it dawned on me I was seeing the ground waves from that quake and I was driving perpendicular to them! As strong as they were, I had no trouble keeping my car under control. The road just felt and looked bumpy.

I do know it is a little different riding a motorcycle, but be assured, Sightseer, that it takes a rather strong quake to make the road hard to drive on. Just keep watch and go and enjoy Yellowstone. I think you will have a great time.

Posted by: Diane | February 6, 2010 1:26 PM

Major plinian ejection, Montserrat, 22:29. Blocked out the camera image at 22:31-33. Spectacular images just before blackout.

FWIW, keep your eye on the Kurils, probably Sarychev Peak for a major uptick in activity.

Posted by: Passerby | February 6, 2010 5:39 PM

Did I read 'Laacher See' in posts 27, 28 and 29 ;-) ? I just love the Eifel volcanic fields. My mother is a geography teacher, and her fascination for geography and especially geology appeared to be contagious (I was still only like five years old at that time). Especially volcanism has always interested me a lot. That's why we went to the Eifel two years in a row for the holidays when I was a kid, the first time when I was 8 years old. I live in the South of the Netherlands, so it's only about two to three hours of driving. Nowadays I go there a lot, every few months or even weeks if possible, just to enjoy being there among the volcanoes and to collect rocks and minerals. Although I think the East Eifel is beautiful and is more interesting from a geological point of view, the West Eifel has an even more beautiful landscape.

I'm going to Laacher See again on February 18. I'll also visit the Rieden caldera ('Hatzenfeld' quarry) and the Dachsbusch scoria cone (which is next to the Wehr caldera).

Posted by: Gijs de Reijke | February 6, 2010 8:57 PM

I was just wondering if some one could help give me some insight. Why do you think there was an earthquake swarm right around the same exact time in 2008 and 2009? Didn't they both start occurring right around Dec 26th? Please correct me if I'm wrong. Also, thanks for taking the time to read this and I appreciate your response.

Posted by: Bas | February 7, 2010 11:43 AM

@Bas: the 2008-2009 Yellowstone earthquake swarm started 26 December, the latest one on 17 January 2010. Thus the starting dates are similar but not identical, and in any case they're coincidence: dates are our way to subdivide time into units. Yellowstone's movements are determined by slow pressure and temperature changes at great depth, and by the overall game of plate tectonics and magma generation within the Earth, which are extremely complex and often random processes. So there is a vanishingly small possibility that the two earthquake swarms occurring during the winter season has any meaning.

#Gijs, although Etna and the other Italian volcanoes are supremely spectacular and fascinating, I do miss the Eifel sometimes. The sweet, sinous, hilly, green landscape with its lakes, volcanic and not, is unlike anything you find here. One day I will have to get back there, surely to show the country of my origin to my little daughter!

There seems to have been quite a lot of increased activity at the Soufrière Hills volcano (Montserrat) this weekend. I don't think it should be called a Plinian eruption as supposed by Passerby - that would have decapitated the lava dome but today's webcam images show it's still very much there. But certainly the volcano is very active, and maybe I'd really go there first right now and then to the Eifel volcanic field in Germany ...

Posted by: Boris Behncke | February 7, 2010 12:23 PM

@ Boris: I was meaning to ask you if you don't miss it :) . I think the Eifel is fascinating to me because it's so close to home. That's why the kids I teach geography always show extra interest when I mention the Eifel volcanism or the seismicity of the graben systems around it when I talk about geology. And I keep going back to it. Events like the eruption of Pinatubo and Chaitén are 'nice', but the Eifel still has something extra. The formation of a new small scoria cone there would probably interest me more than a 1.000+ cubic kilometers eruption at *cough*Yellowstone*cough* ;-) . I think it would actually be good for the Eifel economy if an eruption happened there. The area would attract even more tourists than nowadays.

Apart from the geology of the Eifel: I find the landscapes beautiful as well. I could find myself living in the Liesertal or near the Kleine Kyll in the future. Or maybe in that villa inside the Bausenberg crater ^_^ .

If you ever plan to go to the Eifel again, please let me know if you don't mind ;-) . I'm always in for visiting the area, even more with other volcano enthousiasts (especially if someone happens to be a volcanologist ;-) ).

@ Passerby: the Eifel volcanism is most likely not the result of a 'classic' hot spot. But there's definately a (relatively shallow) plume shaped anomaly beneath the area.

And The Laacher See eruption was actually the only EEVF eruption that is younger than the 115.000 year old Dümpelmaar eruption. The WEVF is the only place in the Eifel that produced eruptions between those two events and after the Laacher See erupion.

If some large eruptions around the time of the Laacher See eruption are indeed more clustered than usual (which I kind of doubt, because eruptions sized like the one at Laacher See happen all over the world more than once every century, and I don't know if there's any data available on if more large eruptions happened then than before and after that period), maybe they're related to isostatic compensation after the disappearance of large ice sheets. But they would also have to be clustered not just in time, but also in space (relatively close to areas that were covered by large ice sheets during the Weichselian glaciation) and I don't know if that's the case.

Posted by: Gijs de Reijke | February 7, 2010 1:54 PM

@Mots: Isn't that the case with parents?! When I was three (don't ask me how I remember, I just do LOL) we went up to Canada at the time the qween was being coronated and one of the things my mom just had to do was go to Buchardt Gardens. I rememeber the trees and bushes and that is about it. At the time, I could not see what the big deal was.

Later, Mom did not tell me that a place in town called Rock Garden was closing down and giving away beautiful rocks! One gal who got there brought a two foot long quartz crystal to school! Rats!!!! I was pretty upset with Mom to say the least.

Under the post on Tungurahua, is a post about it still being active this morning. There have been several explosions.

Posted by: Diane | February 7, 2010 2:15 PM

Well, we have had some "'ahem' healthy discussions"here.:-) I suppose a forum would be ok as long as we stay cordial. I am just thinking of some who might stumble on the site and go a bit overboard. Personally, I like the way it is, but change can be a good thing, too. Then we could have a couple of places to exchange ideas.

Erik, what do you think?

Posted by: Diane | February 7, 2010 4:17 PM

@Gijs: I didn't think of any kind of mutiny ;-D. I think you already know that. I had no idea how to moderate a forum so I was just raising an issue that a friend of mine had a long time ago with a message board. Had to shut it down.

What did you mean by the largest known explosive eruption? A VEI 9?! Which one was that?!! I didn't catch that in your post. Just tells me I need to study more about this stuff which I will be doing as soon as I get that book! It will be a start even if I have had a course in geology. A lot more is known now. Of course, I had no idea there had been a large volcano in Germany.

Learning all the time. :-D

Posted by: Diane | February 7, 2010 7:38 PM

@Gijs: A forum would be a great idea.
I live in Germany, in the Tanuns mountains. There we have only a little unknown volcano "Altkönig". But I know also the Volcano Eifel, which is natural more fascinating. Until now I visited it only two times, but I know I will go back soon, because it is really a beautiful place. I love for example the "Nettetal" in the East Eifel... And in which country is it possible to stay for holidays in a hotel inside a volcano crater, like in the Meerfelder Maar?
Today there was a little earthquake in the volcano Eifel near Daun. It was very little, and not worth mentioning, but because of the Eifel-Volcano catastrophe film last year on RTL, more people were frighten there today than they would be in the past.
I think the film was nearly so good four the touristivc n the Eifel than a real volcanic eruption. -_^

Posted by: Diana | February 7, 2010 7:52 PM

@Randall: Can I ask you what the purpose of your webside is? Sorry but I don't understand it why you are "collecting disasters and things which could frighten people" there.

Posted by: Diana | February 7, 2010 8:29 PM

Flood basalts somewhere maybe? It would have to cause 1600 years of cold.

Posted by: Randall Nix | February 7, 2010 8:46 PM

There is no VEI9 1-8.

Posted by: Randall Nix | February 7, 2010 8:55 PM

Sorry Gijs de Reijke VEI goes from 1-8 Ask Boris or Erik if you do not believe me. It's late here so I don't have time to get it anywhere else for now so I guess this will have to do:
http://en.wikipedia.org/wiki/Volcanic_Explosivity_Index
Like I said ask Erik or Boris and they will confirm it for you...There is no VEI9...there is a something called a Verneshot but that didn't happen at La Garita.

Posted by: Randall Nix | February 8, 2010 4:41 AM

@ Randall: if I may quote from the Wiki-article: "The scale is open-ended with the largest volcanoes in history given magnitude 8." It's the third sentence of the text ;-) . So IF the number of 11.000 is correct, it was a VEI 9.

@ Boris: I totally agree on that. The Germans do know now that there's a potential risk of future eruptions in the Eifel, although more accurate monitoring is needed. Geologists and volcanologists like Ulrich C. Schreiber (I like his book far better than the movie, although I don't really like the part where tholeitic lava blocks off the Rhine) and Hans-Ulrich Schmincke said the same thing in the documentary that was broadcasted after the RTL aired 'Vulkan'.

Btw: to the public just outside Germany (the Netherlands, France, Belgium...) the hazards the Eifel might pose are unknown. Only those who are professionally interested or interested out of a hobby (or both, as in my case) know that there are volcanoes in Germany. A small part of that group knows the Eifel is dormant, and not extinct.

More seismometers, more materials to measure gas emissions, maybe even some tiltmeters... 'better safe than sorry' indeed :) .

Posted by: Gijs de Reijke | February 8, 2010 10:12 AM

The VEI is logarithmic. It means that every level is ten times stronger than the level before, just as in the Richter scale. The limit of a VEI 8 should be 9.999 km3, but until recently no eruption that ever occurred was thought to exceed that limit. That is why no number larger than VEI 8 has ever been assigned to any eruption. It sometimes, like in this instance, causes the misinterpretation that the VEI is by definition something between 0 (non-explosive) and 8. However, like the English Wikipedia article describes, it's an open-ended scale. If the more recent numbers on the La Garita eruption are correct, that is the only eruption known so far that was a VEI 9.

In the end, it doesn't really matter what VEI-number we give these events. They happen, they're sometimes friggin' huge, and the scale is only there to help us understand (just a little bit) of how big these things can get. Personally, I don't care if the scale would be limited to 8 or not. That's not the point of the entire thing ;-) .

Posted by: Gijs de Reijke | February 8, 2010 11:49 AM

@Randall: although Gijs has already given a response to your comment on the VEI scale, let me try to clarify this a bit further.
The VEI, like the famous Richter scale, is open upwards, that is, it can theoretically have any value from zero to ten or twenty or hundred or thousand, only that in real life, we won't get any earthquakes much stronger than 9.5 on the Richter scale, and hardly any eruptions with a VEI greater than 8. But since that gigantic Fish Canyon eruption of La Garita caldera may have produced more than 11,000 cubic kilometers of magma, it must be necessarily given a VEI of 9. In that sense, the Wikipedia explanation is not correct, saying the VEI goes only from 0 to 8 - so it actually needs to be corrected.

Thanks anyway for considering me an authority in the field :-) but count on it, Gijs is no less an expert than Erik and me! And I am really glad that you and other interested people do get the informtion they look for in this forum.

Posted by: Boris Behncke | February 8, 2010 1:06 PM

Boris I am going to try this one more time with no links since it said my comments were being held by the owner of the blog for review. If what you say is true then some better tell the USGS (and others) that they are wrong.

Posted by: Randall Nix | February 8, 2010 2:51 PM

Evince them open hearts if you would hate the penalization

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