SI/USGS Weekly Volcano Report for 12/2-12/8/2009

JT said on the man-made lava comment that he's worried about Anak Krakatoa. That one doesnt concern me nearly as much as Rabaul. I figure Krakatoa would need to re-build its cone to approx the same size as the complex that exploded last time in order to get a similar level of destruction, and thats going to take awhile.

Rabaul otoh seems to just blow up and collapse into the harbor, and theres a lot of activity in the SW Pacific lately.

Maybe we should have a pool on where the next VEI 8 will occur? The winner could get one of those Dinosaur Volcano things.

Fitz,

The idea of a contest to predict the next eruption occurred to me too.

Now, I would set the bar at VEI (Volcanic Explosivity Index) at maybe 6 (or lower).

The Mt. Pinatubo eruption just tipped the scale at VEI 6.
Krakatua was 6.5
Tambora was 7.3
The only 8 on my list Tambora 8.8 was thought to have wiped out most humans then alive. If we get anything that big ... a toy dinosaur isn't going to mean much too much to me. LOL

Great idea though. You probably saved your money and didn't buy the hundreds of dollars in Volcano books that I just got.

My source for those eruption magnitudes was Encyclopedia of Volcanoes p 265

When will I learn to be frugal?

Fitz,

Occasionally I see an earthquake magnitude 5 that is fairly close to Rabaul. I almost commented here about one that happened about two weeks ago.

I haven't been watching volcanic activity for too long - and even if there was a gradual uptick in activity - I am not sure that I would detect the gradual change.

Now, there has also been some big earthquakes far South of Rabaul maybe ( to my uneducated eye ) closer to New Zealand. There has been at least one 7 magnitude quake in the past year or so. But these to me seem just out in the water away from everything else.

Now, if we get a 7 magnitude quake within 50 miles of Rabaul I'd expect something newsworthy to happen there very quickly. :(

Come to think of it - we should probably not have a prize for predicting a volcanic eruption. While to us the challenge is merely an intellectual exercise - others might see volcanic activity as merely bring death and destruction and we wouldn't want to be misunderstood as celebrating that.

Perhaps instead we could start our own danger index - or something like that. Something that will be seen as more reflective of the true concern that volcanologists have for preserving lives. It is certainly for this reason that I am interested in volcanoes - the power of them is certainly astonishing too - and too often people forget that our lives our very fragile.

Correction: I meant that I haven't been observing earthquake activity too long - and I don't know whether or not the South Pacific is getting more quakes. If anyone has any studies confirming what Fitz says I'll be delighted to read about it.

Thomas, there is a reason for all those quakes in the South Pacific. Look at the relative plate motions. You'd be hard pressed to find a faster rate of subduction than that around Tonga (remember the large Samoan quake recently) and I wouldn't write off the Kermadecs too quickly. There have been some big eruptions there in the past. Take a look at Macauley Island.

http://www.gns.cri.nz/what/earthact/volcanoes/nzvolcanoes/kermprint.htm

If theres a VEI 8 and all of humanity is wiped out, I'm DEFINitely gonna spend some of my final time getting one of those dinosaur things. In 65 million years when some smart dinosaur digs me up, it'll freak em out.

When they tested the first atom bomb, all the scientists had a pool on the size of the blast. Our pool wouldnt be quite that morbid. I do see some merit in having a "DANGER INDEX" that Erik could post as a peer prediction, sort of the way the Bullitin of Atomic Scientists do their Doomsday clock. Theres a scientific term for it which I dont know, but the more people you get to make an educated guess on something, the closer to a good answer you generally get.
Have a list of potential next eruptions and what size we guess they'll achieve.

Ok, let's start with MachÃn then ;-) .

After that, we can do Campi Flegrei, Long Valley, and Taal. Not that there's something about to happen at those places, but just to have some fun if the press gets hold of our predictions and starts writing about it ^_^ . However, I don't really know if Erik would be happy if someone would refer to this blog when all kind of doomsday stories get out into the open ;-) . Maybe something for an April Fools' joke ^_^ ? Let's see if we can p*ss some people off at Mammoth Lakes again XD .

Nah, but for real: trying to predict some eruptions would be very interesting. Recently I posted the idea of a messageboard connected to the blog in the 'Eruptions suggestions thread', and I think that this subject would fit well on a forum.

http://scienceblogs.com/eruptions/2009/11/eruptions_suggestion_thread.p…

Bruce Stout,

I think I'll get some dinner and maybe a glass of wine and start nibbling at that article you provided the link for which (when pasted into Microsoft Word) is 25 pages or 11,000+ words long and very, very informative looking.

Looks like Soufiere Hills is getting ready to get more dangerous and explosive.

Thursday, 10 December 2009 16:54

Hazard level raised to 4
At 6:40 am on 10 December, 2009 a large pyroclastic flow travelled down Tyers Ghaut. This pyroclastic flow reached to below the west end of Lees village in the Dyers river, some 3.5 kilometers from the lava dome. This point has been stated by the MVO as the âTrigger point' for raising the hazard level from 3 to 4.

Ha! Thomas, I see we share a couple of interests! The Geonet article is a bit dated unfortunately but still quite interesting. There are quite a few large submarine calderas between NZ and Tonga, whether any of them would result in a large subaerial eruption remains to be seen. The 100 km3 estimate for the Sandy Bay ignimbrite on Macauley looks like it might be a bit excessive. the GVP puts that eruption at VEI 6 but I don't know of any recent research on it.

Setting up a betting pool would be fun, but considering the geologic time of events, the value of the pool diminishes quite a bit over time, both monetarily and also psycically as interest fades during the long wait. Another approach would be for the participants to invest in some consumable that increases in value (cask of scotch for example) and pays out to either the winner or his/her heirs. And if the event turns out to be of a civilization ending nature, those that can get to where the scotch is stored can go out in style, kind of like the scientists at the remote station in the Day After Tomorrow.

I personally am not worried about Rabaul too much - that volcano is venting continuously since 15 years, so it seems to be more in equilibrium than before the eruption started in 1994. Neither am I too worried about the absolutely cataclysmic scenarios because the odds are none will happen during our lifetime (maybe none even while humanity is still there), but I am very worried about all the s**t going down in everyday life, starting from car accidents and slipping in the bathtub and so on. I am worried about the chance that climate will change so rapidly (with or without human influence) as it has apparently done in the past, as new geological studies reveal, and I would recommend that humans avoid whatever possible negative influence they MAY have on climate.
And yes, I am worried about some bad volcanic catastrophe to happen one of these days, but I fear it will be from a volcano that nobody is thinking about these days ... none of those cliché places like Yellowstone, but some unconspicuous volcano like Chaitén was, or Cerro MachÃn is.

We're probably very "fortunate" to have experienced both Mt St Helens AND Pinatubo in our trivial little 100 year lifespans. And we just missed Novarupta and Krakatoa, on a geologic scale.

My money for the next big one (VEI 6+) would likely be some big hole in the ground that almost nobody has ever heard of, or just next to one. Somewhere in the S Pacific, Kamchatka or possibly Japan. Economic disruption is what will most likely affect us, and a caldera event in Japan would surely do that.

And Boris, remember the TV comedy skit about the 2 depressed Airline Pilots? They're positive they'll die any second in a plane crash. Then one reminds the other that flying is statistically no more dangerous than crossing the street. So the other says "Yes, but after we land, we have to do that too."

I'd put pins in yellowstone, the German Eiffel region and that Volcanic complex outside rome, All just sitting like silent assasins waiting till nobody looking....

Among the Usual Suspects, I'd also add Taupo...long history of major eruptions. But I'd agree, it will likely be some long-quiet centre with no historic activity (and probably, Sod's Law being invoked, one which has never been studied in detail) My guess for likely areas would be the SW Pacific region, Alaska Peninsula end of the Aleutian arc, or the high Andes

Because...?

The Eifel would be 'nice' however ;-) . VEI 5-6 just South of Laacher See... If it happens, I think the old Drachenfels lava dome near Bonn would be a very nice place to use as an observatory. Who's joining me ;-) ?

Note: the 'Because...?' in my previous comment was meant for Stephen Tierney ;-) .

Because ? Wow..didn't expect to be put on the spot Gijs.
Ok I not as clued up as you guys (or gals) and I learn from you all everyday. So I respect you all...

My humble gut feelings is that we know a little less on caldera eruptions but we know they reocur over thousands or tens of thousand of years. Some just show enough activity to keep us interested some possibly lie undescovered.

I wonder if we might witness a volcanic collapse into its own magma chamber?? Which volcano could be a possible ne crater lake? Etna? Mauna loa?, Maybe mt Fuji Presume it would be one of the bigger one's.Just guessing all input welcome.. (go on tell me off lol)

jeepers, I'd say anywhere on the pacific rim, add Indonesia and the Rift Valley (think flood basalt), Iceland, possibly Italy or Greece, so in other words it's probably going to be Antarctica.. ;-) crikey I don't know. .. the Eifel, why not?

I watched a recorded TV program a couple days ago. It is part of the NAKED SCIENCE series that was titled something like Vesuvious: Ticking Time Bomb.

I learned a few interesting things about the 79 AD eruption and the eruption that took place about 2,000 years earlier than that one.

They noted that a strong quake hit Pompei in 62AD - 17 years prior to the big eruption. They also noted that the locations where people were building buildings gave evidence of a fluctuating coastline -- evidence of a lot of inflation and subsidence in the Vesuvious area prior to the 69AD eruption. Sometimes buildings weren't near the coastline. Othertimes the sea came in much closer and they needed much higher sea defenses. They didn't have real clear dates - I don't know if this subsidence and inflation took place over hundreds of years, decades or just years - but the sea level in relationship to the coastline seemed to me to easily vary several meters. Waterlines were evident on buildings - and yet these buildings were on top of other earlier buildings that were once built above sea level.

It is just evidence that sometimes a volcano can be very active (swelling and subsiding) for many years and not erupt. So perhaps Machin could be on a long ramp-up and erupt in another decade - or more? I'd like to keep an eye on the Lazufre area (in the Central Andes) too - and try to figure out if there has been unusual earthquakes in that area that is accompanying its' slow inflation.

Perhaps more interesting (or dangerous) about Vesuvius is that the eruption that took place 4,000 year before present ( about 2,000 years before Vesuvius buried Pompeii ) sent a Pyroclastic flow over the area that is now Naples. A strong eruption like that one was isn't the basis for current emergency planning around Naples. It is much easier to plan for the smaller and midsize eruptions. The TV showed experts pointing out that the arbitrarily selected zoning of what is a dangerous area near Naples now has a hospital being built outside the danger area - but the hospital is still being built on top of a Pyroclastic flow from about 4,000 years ago. So is the area really safe for a hospital? But, then again would building the hospital a few meters beyond the Pyroclastic deposit be guaranteed safe either?

Another thought is that it will be very frustrating for residents, volcanoligists, and public officials, if Vesuvious does undergo a long ramp up of activity that takes decades to culminate in a big eruption. (This though is still much preferable to an eruption that gives insufficient notice.)

Anyway, I just thought I would share what I learned from a TV program. Now, I don't think there was any mention on the TV program about Camp Flegrei - which also needs to be monitored.

I am still totally ignorant about Eiffel(sp?) in Germany.
I kind of agree with Boris Behnke about Rabaul. However, the whole tectonic plate is so seismically active and I think there is probably a big magma chamber there - I'd worry something big could happen if there was a strong quake right in the area.
And I am still trying to wrap my mind around another big magma region (The Taupo ....) I haven't researched it yet either.

I also got the feeling that Erik has wanted us to select Ruapehu for a volcanic profile. I think Erik may have visited there - he may know a lot about it and I'd be much delighted if he would share with us his knowledge of a volcano that he has extra familiarity with.

Best to everyone!

The Eifel volcanic field in Western Germany is an intraplate volcanic area with a long, long history of intermittent eruptions. Most of these are basaltic, cinder-cone and small lava flow-forming events, similar to the San Francisco volcanic field in Arizona and the Michoacan volcanic field in Mexico (the one that last erupted forming Paricutin in 1943-1952). The interesting thing about the Eifel is that every now and then it also produces larger, silicic, and thus highly explosive eruptions that today would cause significant devastation. The latest such eruption was that of the Laacher See (Lake of Laach) eruptive center about 12,800 years before present. The magnitude of that event was similar to that of Vesuvius in A.D. 79, as was also the chemical composition of the emitted magma (phonolite). Pyroclastic flows filled nearby valleys down to the Rhine river valley, blocking the Rhine and causing the formation of a temporary lake. When the dam broke and the lake drained, flooding occurred downriver in areas now occupied by towns like former Western Germany capital Bonn and Cologne further downstream. We wouldn't like to see something similar happen today. In any case, as always, the probability of a relatively small, cinder-cone forming, Strombolian eruption with lava flows of limited extent and impact is much, much higher. Yet, German television RTL has recently aired a two-episode fiction about a new Laacher-See-type eruption in the Eifel ... a pyrotechnic spectacle packed with the crème de la crème of contemporary German actors, and with special effects à la Supervolcano or Dante's Peak including tomato sauce basaltic lava that wouldn't happen at all during that sort of eruption - worth looking at for some of the special effects but forget about the human part of the story. Some info is here: http://www.imdb.com/title/tt1266601/

@ Stephen: no offence meant ;-) . I'm just very interested in what makes people here think that there's maybe something going on at those volcanoes (among others) that's worth looking at a little bit closer. For the Eifel and Colli Albani it's obvious: both areas don't get enough attention at this moment (especially the Eifel). Yellowstone on the other hand is being monitored very well, and 'the world' knows about it's potential. And if I'm correct, the nature of gas emissons from yellowstone are currently not very alarming. I read somewhere a couple of years back we 'should' be ok for at least the next 10.000 years or so. But what does that mean at a volcanic system we've never seen in real action before... New surprises pop up every once in a while, like the speed of the rhyolite under Chaitén... Yellowstone is rhyolitic as well... Can we apply what we learned from Chaitén to Yellowstone?

@ Thomas Donlon: The Eifel has two quartenary volcanic fields: the West Eifel and the East Eifel. Most of the volcanoes there are scoria cones and maars, but in the East Eifel a group of small calderas can be found. The most recent eruption in the East Eifel occurred around 13.000 years ago, which also happened to be biggest eruption of all eruptions in the Eifel so far. It happened at what is now known as Laacher See, and ejected an estimated 6.3 cubic kilometers of phonolitic to trachyphonolitic materials. A devastating eruption at that time, but there are hunderds of thousands of people living and working in the area nowadays. An event of that size would probably also do a lot of damage to the economies of Germany and the surrounding countries. Although we think the area is relatively quiet right now (some 'mofettes' can be found there, and small, shallow earthquakes occur regularly just South of Laacher See), the problem is that there's almost no monitoring of what's going on in the East Eifel. There are currently three permanent seismometers keeping an eye on things, and for as far as I know no permanent equipment to measure gas emissions.

Hans Ulrich Schmincke has a very nice chapter on the Laacher See eruption in his book 'Volcanism', which is by the way a must have for anyone who's really interested in the subject.

Here's another bit of info: the KVERT web site (which is about the monitoring of volcanoes in Kamchatka and the northern Kuriles) has new photos of Kliuchevskoi (or Klyuchevskoy), a huge and extremely active stratovolcano that is again erupting since a few months: http://www.kscnet.ru/ivs/kvert/current/klch/index.html
These latest photos show a new cone growing at the summit of the volcano, which to me appears larger than those formed during the previous eruptions in 2007 and 2008.

@ Herr Behncke: you beat me to it ^_^ . Didn't see it till I posted my comment.

to Gijs: the Laacher See eruption was not the most recent volcanic episode in the Eifel volcanic field, but there have been two maar-forming events at the Ulmener Maar (about 8740 years ago) and at the Pulvermaar (about 8300 years ago), that means they're Holocene age.
The Eifel volcanic field is not very well known internationally but in Germany there is now quite some awareness that it's potentially active (not only since that RTL fiction a few months ago), and it is actually monitored, so any precursors (if there are) should be well recognized. This awareness is due to the work (including a massive public outreach effort) of Hans Ulrich Schmincke and many collaborators since the 1970s.

to Gijs once more ... it is true that the monitoring equipment in the Eifel is nothing like the instrumentarium that we have all over Etna and Vesuvius and even the Colli Albani.
And I wonder what would happen if ever there would be a clear increase in signs of unrest, what response it would cause in Germany. That country has experience with disasters such as flooding and heavy gales, and occasional landslides, but certainly not with volcano emergencies.

Last bit concerning Laacher See - for those capable of reading German, you can download an interesting article by Conny Park and Hans-Ulrich Schmincke about the Laacher See eruption and subsequent flooding of the Rhine valley here:
http://www.wissenschaft-online.de/artikel/979373

To Boris: Yeah, I meant the East Eifel. The West Eifel has indeed seen some more activity after the Laacher See eruption. Even the Dauner Maare formed after that (Schalkenmehrener Maar around 11.000 years ago, Gemündener Maar around 10.750 years ago, and the Weinfelder Maar around 10.500 years ago). With the RTL-movie came a documentary, which is now online at youtube. Ulrich C. Schreiber describes the lack of monitoring in the Eifel, so that's where I got my information from (although the documentary is meant more for those who don't really know a lot about volcanism). Documentary on youtube: http://www.youtube.com/view_play_list?p=70E792B55330AE5E&search_query=A…

Another very interesting area is the Massif Central in France. Comparable to the Eifel (young volcanic fields), only more complex. I wouldn't want to live in Clermont-Ferrand...

Just a frivolous thought (apologies in advance)..but if there is an eruption in the Eifel field with a high Plinian column, could Germany claim that, for a few hours at least, it had its own Eifel Tower?

Sorry, it already exists ;-)

http://de.wikipedia.org/wiki/Eifelturm

Bruce Stout:

The link you provided in comment 5 was very interesting. It appears that it is one booklet (put online) out of a collection of booklets. Do you know if the other booklets are online too? And if so where?
And why I am too lazy to Google it myself? Actually I've run out of time at the moment. A few more posts I have to make.

Boris Behncke: The KVERT website (linked from comment 23) has some great volcano pictures. The most intriguing one for me is the one taken on 17 August 2007 and the cloud hanging on the top of the volcano.

I was just pondering that many volcanoes that will have the most powerful eruptions aren't always going to be the very tall ones. They would blow themselves apart with a very powerful eruption!
Calderas of course are often powerful. But some types of little volcanoes (Chaiten) - and even Mt Pinatubo wasn't that tall yet they packed a big punch. I guess I am going to have expand my thinking of what a powerful volcano is.

You did help enlighten me about the Eifel volcanic field - and you have helped enlighten me about other things too here at this blog and at Dr. Harrington's blog.

Gijs de Reijke:
You were also helpful in helping me understand the Eifel volcanic field. The link you provided to the Youtube video (in German) was worth watching (at least part 1 was) for me who doesn't speak German. The video was so well done that I watched the rest of the approximately 10 minute segments too. (I think only the first one though - jumped across the language barrier.) I am left wondering if there has been active quake activity in the area - they were showing seismograph recordings. They also showed some maps of areas that might be in danger if they had a big eruption.

I appreciate you reminding me about the book 'Volcanism' which I actually just bought about a month ago - along with several similar books. The graphics in the book are very good and the topics presented in it do interest me. Unless I find a more exceptionally well-written volcano book in my tiny collection - it might be the first geology or volcano textbook that I complete reading.

I am just curious: Your name isn't typical American fare and you have knowledge of German. Do you live in Europe?

Bruce Stout: You have a good knowledge of the dynamics of the East Pacific plate. Do you live in that area - Australia, New Zealand? I have a vague memory that some contributor to this website was from that there.

To Non-US residents: I like that people bring to this blog a knowledge of the geology of their parts of the world. A while back there was some earthquake activity in Saudi Arabia and some people from that region helped bring us up to speed on the volcanic and geological history of the area. I assume that the earthquakes in Saudi Arabia have gradually become less frequent and there is no immediate threat of one the many little volcanoes there erupting.

To all the readers and contributors from around the world - I (and I think many others) appreciate your perspectives and insights.

I wish to state that I am Officially Appalled at the coverage that Calderas receive in general, and Wikipedia in particular. Wiki only lists 7 or so in America, And I've found 6 just in Nevada.
If I was the sort of person that did such things, I would put some effort into updating Wiki, at least the America section, which is pathetic. Or maybe I'd do it if I had a clue how. I've never submitted to Wiki.
Or maybe we could all pick a region and research it thouroghly (sp?) and someone with some free time could do the submitting part.

Fitz,

I wholeheartedly agree with you on the lack of an easily accessible, visually friendly database of Caldera eruptions. The Smithsonian (I recall) has a few databases (one is in EXCEl format) of the most powerful eruptions that have taken place in the world.

If no one else does a better job categorizing all these volcanoes, and putting them on the web by area - it just might spur me to categorize them and put them online. Wading through technological options to do this is rather time-consuming. Better get my new computer set up so at least I can run Google Earth!

I was wondering if Rabaul is spitting out sand every few minutes as it did from 1996-2003 - but Boris Behncke's comment has me wondering if Rabaul ever stopped that pattern of eruption since 1996. It's extremely unpleasant living near a mountain that spits sand every few minutes and corrodes just about anything with sulfuric acid, and yet people still live there. Imagine what a nuisance Stromboli would be if it threw up sand rather than molten rock.

@ Thomas: yeah, I'm Dutch actually. In fact, I live only 2½ hours of driving from the Eifel.

Just to add some nice calderas to the topic:

- The 'Monts Dore caldera' (also called 'Haute Dordogne caldera' and 'La Grande Nappe' (The Big Napkin)) that formed around 2.5 million years ago in the 'Massif Central' in France. It ejected an estimated 8 cubic kilometers of rhyolitic ash and pumice
- The Sancy caldera. I don't know the dimensions of the caldera forming eruption(-s), but it happened between 250.000 and 1 million years ago. Most of the materials that can be found there are trachyandesitic.

A nice picture to go with the French volcanoes I just mentioned: http://img197.imageshack.us/img197/3724/montsdorepuydesancy.jpg

I have good lists so far for some of the Western US and E Africa.
Italy has several, theres at least one in Bulgaria. I have 1 caldera in Virginia. Theres supposed to be a volcanic belt from Ohio to Texas but I've only found mention of Taum Sauk in Missouri. There are several old caldera in SW Texas.

W Europe, Russia, Kamchatka, Japan, China/Koreas, the Philipines/N Pacific, W Africa, Central America, Alaska and Canada would all deserve a good days research each. The Andes and S Pac/New Zealand would be tough regions to look at.

The Holocene volcanos are pretty well covered on the net, but once you go past 10,000 yrs you mostly see the standard areas. If you find one, get the name, age, location, size in km or miles, and possibly how much ash/lava it ejected, or the thickness of its tuff, and where you found the info.

Anybody got a site which will show current detail of the flank eruption of etna? Ta

Boris,

thanks for that link to the Schminke and Park article. Very, very interesting. Taupo also had a similar effect on the Waikato River after its last big eruption. The lake level is estimated to have been something like 20 m higher (quoting from a shaky memory) after the eruption until a tephra dam broke and actually changed the course of the river. What is interesting is how fast the Rhine managed to create a lake of that size. It was just a matter of days!!! That doesn't leave a lot of time for disaster mitigation. Also fascinated to see quite how high the tephra fallout was so far from the vent. That looks larger than a VEI 6 to me (judging by Taupo and Pinatubo) but I'll accept the experts' assessment: 5 - 10 cm ash fall all the way to the Swiss border? Wow.

PS here's a link to the paper on the ephemeral lake following the Taupo eruption:
http://books.google.de/books?id=JF8kUBhLvFoC&pg=PA109&lpg=PA109&dq=taup…

Fitz,

You can open up this page
http://www.volcano.si.edu/world/list_allnames.htm

With a PC just hit CTRL F
and then type in Caldera and you will certainly get more than a hundred hits - I am guessing 300 hundred ... but I stopped counting just a little way through the page when I reached 50.

Also on the side of the page if you want a summary document in Excel format and are proficient with the program there is a link for an Excel summary. I am not fluent with the program and am not sure that I could search through it. There may even be somewhere on the site a different Excel sheet of volcanoes that is not a summary.

There is a book called Caldera Volcanism. It is about a hundred bucks. I just got it, haven't yet read it, so I am not in a position to suggest that you buy it.

Also, I noticed at the same site (above link) there are now placemarks for volcanoes on Google Earth. Until I get my new computer set-up I can't comment on that either.

Best to you Fitz.

Gijs de Reijke: My mother came over to the US from the Netherlands in her early 20's. I visited Holland many years ago as a kid with my family. We saw the windmills, dikes, cheese markets, tulips, barges, Rotterdam, turning restaurant on the tower, miniature city and so many people spoke great English as they at that time watched many American TV programs with dutch subtitles and also took English in school from a young age.

At the time when my family was visting my parents were commenting there were no fat people in the Netherlands. Maybe now that we've exported a bunch of American fast food restaurants that has changed.

Oh well, I am half dutch too.

TTYL

Thanks TD, I've been in the Smithsonian site a hundred times and didnt know you could do that.

Unfortunately, as good as it is, I have found a bunch of calderas missing from that list. Taum Sauk, Mt Rogers and Questa arent in it.

I fear a lot of research is in my future.

@ Thomas: we got used to having subtitles. The Germans and French for example use voice-overs for nearly everthing that's not spoken in their native language. The Germans can compensate for that somewhat because English and German are Germanic languages (as are Dutch and some Scandinavian languages), but the French speak a Romance language. That's why they usually have more trouble learning English.

Windmills, clogs, tulips, cheese... I guess every country has some things to keep the tourists happy ;-) . Nowadays it's more the Amsterdam red light district and some 'smokable herbs' ^_^ .

The Rotterdam harbour is by the way one of the places that would get really affected by a Laacher See like event in the Eifel. Most of the ships that go into Germany from Rotterdam use the Rhine to get there. Apart from that, the harbour itself would probably get a lot of ash and pumice through the Rhine to deal with.

@ Fitz: are you 'just' looking for Holocene calderas? 'Cause I happen to know some older ones, starting with some nice Devonian calderas located in Scotland, like Glencoe and Ben Nevis ^_^ .

oh far out, I just checked out the Alban Hills in Google Earth. It's not just Naples that's sitting on an active caldera system, Rome is too!!! I had no idea. Once again, hat tip to Boris! Enter these coordinates into Google Earth:

41°44'0"N 12°42'0"E

you'll get the idea. Even a small phreatomagmatic eruption from one of those maars could have huge consequences.

I know a good website on Italian volcanoes, which I've been using a couple of years now. It happens to be the site of someone called 'Boris Behncke' ;-) . Coincidence ;-) ?

http://boris.vulcanoetna.it/ALBANI.html

Great stuff! The geological map gives a good idea on how big Rome's problems could be if there would be a big eruption.

Italy has some very 'nice' calderas, but one of the geomorphologically youngest looking volcanoes doesn't appear on the GVP-site because of it's age: Roccamonfina volcano, which was apparently active between 630.000 and 50.000 years ago. Isn't there any activity left there that might suggest the thing's dormant? Vesuvius and Campi Flegrei are just around the corner, and Colli Albani isn't that far away as well.

Yes, all the way back. Most caldera are long extinct, and of little concern, but its still fascinating to find out how close you might be to one.
I'd say send all the info to my disaster website, but frankly, its a lousy website and I dont want to pilfer any of Eriks audience.

Gijs: I cant find anything on a caldera under the Netherlands, but some quick surfing found you're on top of the Lower Rotliegend (Layer) from 300 Million yrs ago, which is flood basalt and tuff. And the Silverpit Crater is near you to the west I think. Possible meteor origin.

In the Netherlands we have one caldera (for as far as I know): The 'Zuidwalvulkaan' (literally translated: 'South Wall volcano'). It's around 152 million years old, and was active for about 12 million years (Kimmeric orogenesis). It's summit is now buried under 2 kilometers of sediments. It's base can be found at a depth of 3 kilometers, and measures 20 by 35 kilometers. A caldera has been found near the summit, and is probably around 8 kilometers wide. Volcanic ash has been found on the flanks of the volcano, which suggests the eruptions were explosive. The Zuidwalvulkaan is located under what is now the 'Waddenzee' (Wadden Sea). The volcano was discovered after a company called ELF Petroland was searching the area for oil in 1970.

Location and a magnetic anomaly map of the Zuidwalvulkaan: http://www.natuurinformatie.nl/sites/ndb.mcp/contents/i000311/ovn-fig16…

Calderas in Scotland: Glencoe (rhyolitic) and Ben Nevis (both Devonian), Isle of Arran, Ardnamurchan and Isle of Rum (Tertiairy). I'm not aware of any other calderas in Scotland, but there are so many old volcanoes there that I could be wrong. Glencoe was the first caldera ever described as a piecemeal caldera. In Wales lies the rhyolitic Snowdon Caldera (Ordovician).

Gijs: What is the status on the 'caldera list' of those where no visible trace now remains thanks to erosion, but one very probably existed at one time? I'm thinking of the Tertiary volcanics of Western Scotland. The islands of Mull and Skye are both mostly basal wrecks of massive basalt shields, which quite probably had summit calderas during their active life but have been deeply excavated -on Skye to the level of a gabbroic former magma body (the 'black' Cuillin Hills)

Ah yes, Skye and Mull. I forgot about those ^_^' . Mull definitely has a caldera, but I'm not really sure on what happened at what is now Skye. There are remains of concentric intrusions (dikes in the form of 'cone -sheets') above what was once the magma chamber, so it wouldn't surprise me if there ever was a caldera.