Lost Weekend…

Photograph from Wikipemedia Commons. Menengai Caldera in Kenya, one of the largest calderas on the planet.

How to kill a weekend.

As some of you have observed, last week I asked for anyone running across a caldera size and eruption volume to give me a quick shout here on the forums. Ostensibly, I was going to compile a spreadsheet in order to look at Hagstrum’s hotspot list compared to large caldera locations. Despite Carl’s disdain for the Antipode Impact idea, I think Hagstrum’s hotspot list is still pretty good, and it collates several other lists and weeds out some of the less than accepted ones.

While trudging through the calderas that were readily supplied, grabbing what info I could and trying to stay focused on DRE, the question of DRE again came up again in discussions. It wasn’t an actual argument or disagreement, but it did give me enough doubt in my data to seek other sources. Along the way, I found “Sulfur dioxide initiates global climate change in four ways” by Peter L. Ward. Well, to be truthful, I didn’t find that first, I found his table that supports his paper. I had to dig around to find the paper. I HIGHLY recommend the table. It is awesome. While the focus is on SO2 and climate change, they include the names of the tephra deposits that go with specific eruptions. Not all, but quite a few.

From his table, and with the re-worked VolcanoCafe user provided data, I came up with this (distraction#1) :

The first thing I would like to point out, is that it’s a log-log plot. The formula is a bit cantankerous to work with in Excel or on a calculator. (uses 10 raised to a power from a function that then has a logarithm in it.) The log-log plot was the only way to make it come out halfway usable. This formula was derived with DPlot, and in order to minimize the sigma fight (which I lost, quite readily) I left the individual points in place so that you can see just how far the estimate can be off. In one incarnation, I came up with the estimated value being within 0.77 of the actual value, 75% of the time. At this point I needed a beer and would continue later.

Moving back to the plot, and poking around in the text of the paper, I found that Professor Yukio Hayakawa of Gunma University (Japan) had compiled a list of large eruptions covering the last 2000 years. I had to go find that. Unfortunately, the list cuts off at 1999 with the eruption of Hudson in Chile. Distraction #2 involved updating the list with everything that happened since. While using his calculation of eruption magnitude, I decided to look back at how some of the calculations compared to fresher data from GVP. The paper uses M=log(m) -7, where m is the erupted mass in kg.

That’s actually a pretty handy formula. It sort of tracks with the VEI range, (but it’s not VEI, that’s different) Eyjafjallajökull comes in at 4.62, Merapi at 4.55, and Sarychev Peak at 5.04 when using GVP combined lava and tephra (DRE) volumes.

Photograph from Wikimedia Commons. The Somma caldera of Mt Aso in Japan.

I did find a problem with the data though… it wasn’t lining up with GVP info very well. In general, it was running 1.13 times the Hayakawa data when redone with GVP info. Then I ran into the problem of GVP not having anything more than a guesstimate for the VEI of some of the volcanoes with no tephra or magma volumes listed. (and these were pretty recent eruptions) Since Hayakawa used a lower cutoff of M=3.8, anything less than a VEI-4 would not get that high. (VEI=3 yeilds an M of 3.43). Ehh… give up and go find something to gnaw on. I did find out that my stepson had retribution against the Pelicans. I had skipped the King Mackerel fishing since I was “in the groove” with the data. The bait fish they were using had a tendency to attract the Pelicans attention but was so swift that it would be gone by the time the bird got to it.

Referring to Carl’s “Did you notice the erupting Supervolcano?” post, you will note that in the reference, it doesn’t state what the size of the Tondano Caldera eruption was. Being focused primarily on the geothermal energy capability of the system, that is understandable. Using the outline from Figure 5 of the paper, and applying our handy formula, we can get a ballpark estimate of how much “stuff” was involved. At roughly 30km by 9km, it comes in at 197km³… give or take. Solid VEI-7, but the calculation has a sigma of 351km³ so it could quite easily have been large enough to be withing spitting distance of VEI-8. (900km³ is within 2 sigma, and VEI-8 is 1000km³) 

[Editors remark (Carl): I actually was a bit more devious than that. For this caldera I have a bit more data. Through drill core samples I know how much of the caldera is infilled with original ash and later ash. That gave me the actual depth of the original caldera bottom. One should recognize the difference between a subsided caldera and a blow out large caldera event. The first one gently drops with lost material, the other ejects more material due to explosion, in this case when the ocean hit the magma inside the magma chamber. I then calculated the amount of DRE by size. To get a low enough number I did not assume that there was anything ontop, ie. that the volcano was flat with the surrounding landscape. I then got a 918 km^3 of ejected DRE. Size is not everything as I discovered, depth is equally important. Add a couple of the known active volcanoes before the large caldera event and you are comfortably at the 1000 cubic range for a comparatively small caldera. I then did a sanity check against known ash depths for the layer across distance, and fount it to be within the ballpark.]

Okay, back to the data. In 2009, Deligne, Coles, and Sparks put out a paper entitled “Recurrence rates of large explosive volcanic eruptions”. Yet another kick arse piece of work. In it, they use Extreme Value Theory to attack the problem of recurrence rates of large eruptions. Now that is something that I can appreciate. Extreme Value Theory deals with the failings of the Gaussian curve… out there in the tail, the realm of the infamous Black Swan that I am always yammering about exists. I have to go back and read that paper. Anyway, they mentioned Hayakawa’s list, and then using those methods, took the list back to the last 10000 years. Hmm… what can we do with that? I have the Greenland Temperature from the ice core data available, so I plotted it. It didn’t look that interesting until I ran an integral of the M value, then detrended it. That brings out the relative change in the sum that is going on without the actual data trend obscuring it. Plotted against the temperature, it look… “interesting”

There are a couple of peaks that seem coincidental, but for the most part, not a flipping thing there. I found it interesting that there was a peak in activity about 3527 BC and over all, volcanic activity has been declining ever since. I don’t know why that is. That’s just what it looks like. Being a glutton for punishment, and since it was “just sitting there,” I ran a couple of correlation routines on it to see if anything was present, but not obvious. Pearon’s correlation coefficient of 0.0111. Okay, I didn’t really expect a linear correlation. Spearman’s rho is supposed to be able to detect non-linear relationships, and I expected a higher score. I got 0.0017. What? It’s worse? “Wow.”

I have, on this computer, a program called “Formulize” by Eureqa. It’s free, unless you want to use a server farm. You can set it up and run it on your on PC and it will churn through whatever data you feed it and try to find a formula that relates the data sets. It’s the ultimate “beat the data with a stick” program. It can yield garbage… (generally if you feed it garbage) but it’s pretty good at coming up with something. So, I turned it loose. It turns out, that if you have a delay of 1405 days, it can roughly predict the temperature in Greenland from the running detrended integral of the Volcanic activity with a correlation coefficient of 0.7177. (Actually pretty good considering where we started out from) I calculated a sigma for the function based on what the formula predicted and what the actual data was.

That… was distraction 3.

What’s it all mean? Beats me. Greenland is just one point on the globe. There seems to be a 1405 and 1422 day delay relationship in the data, or about 3.8 years. Formulize also ground on a 4.13 and 4.44 year offset for a while. It was quite fun watching it dance back and forth with the delay. Make of it what you will.

And now the all important caveat: I am not a Geologist or trained in any of the fields that have been touched on in this post. My specialty is electronics and cross correlating threats… if you must know. (such as the 230 knot Shvall torpedo tested by Iran having been designed for 533mm torpedo tubes postulated as a design criteria… and the the Kilo class sub launched from Bandar Abass last week or so, having six 533 mm tubes. And that’s all from published data in various sources on the web.) But.. I don’t do that anymore. Volcanoes will have to do.

What to take away from this post, something that can be used by my fellow volcanophiles, is the first plot. You can find a hole in the ground in Google Earth and do a ballpark estimate of how much material may have come out of it when it initially formed. Remember that it may not have all happened at once.

Several thousand years of activity can produce the same effect.

Enjoy!

GEOLURKING

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Sulfur dioxide initiates global climate change in four ways – Ward (2009)
http://tetontectonics.org/Climate/SO2InitiatesClimateChange.pdf
And the table:
http://www.tetontectonics.org/Climate/Ward2009TableS1.pdf

Hayakawa Paleovolcanology Laboratory
http://www.edu.gunma-u.ac.jp/~hayakawa/English.html

Recurrence rates of large explosive volcanic eruptions – Deligne, Coles, and Sparks (2010)
http://www.globalvolcanomodel.org/documents/Deligne%20et%20al%20(2010).pdf
Data Set
ftp://ftp.agu.org/apend/jb/2009jb006554/2009jb006554-ds01.pdf

The pain filled issue with Ischia

Photograph by Giovanni Mattera. Castle Aragonese seen from Ischia. The castle is sitting ontop of a resurgent dome plug from a flanking vent.

The World’s most ill begotten piece of real estate – Part III

The Chinese have a saying, “May you live in interesting times”. And it is in no way a friendly thing to say; on the contrary it is a rather magnificent curse. In Naples people live all their lives in interesting times. If it was not enough with being the poorest city in Italy, they also have to contend with the Camorra (local mafia), drug-wars, corrupt politicians, strikes and general civil unrest. To top it off even further they have built their city on top, or around, no less than 3 active super volcanoes. Could the times get more interesting than that? Well you could add large earthquakes and tsunamis to the list.

Ischia, or more correctly Monte Epomeo, started it’s activity about 350 000 years ago. Technically it is of the complex volcano type. During the first 300 000 years it grew and developed a large edifice paired with an over-sized volcanic sub-structure.

56 000 years ago the volcano had reached the critical level where the edifice was too large and heavy to be sustained on top of the very large magma chamber. The eruption probably started as a very large VEI-6 eruption that emptied out the magma chamber sufficiently for the roof to collapse. And since Ischia is an Island it then got messy as the ocean roared down into the open magma chamber. The ensuing VEI-7 explosion created the Green Tuff Ignimbrite. This Green Tuff Ignimbrite should not be confused with the even larger Pantelleria Green Tuff (Italy is rather interesting…) that covers most of the Mediterranean area.

Photograph showing Sant Angelo D’Ischia, another resurgent dome from a flanking vent.

After the eruption the Island was completely gone. As far as is known a 23 000 year long period of dormancy followed, but there might have been minor subsurface eruptions that helped to start healing the roof of the volcanic chamber system.

33 000 (Ar/K-dating) years ago a new phase started where the volcano had frequent effusive eruptions that helped to weld the tuff together healing the roof of the magma chamber along the entire 10 kilometer wide caldera.

28 000 years ago things started to get really interesting. By then the roof above the chamber was sufficiently structurally sound to hold for the increasing pressure inside the chamber. That caused the entire roof to be pushed upwards.

Most of the readers in here are familiar with the concept of resurgent lava domes. We have all seen them being pushed out of craters like odd plugs. For those interested in seeing the phenomenon I recommend Soufriere Hills at Montserrat. Thing is though that it is normally smaller craters that suffer from this rather dangerous condition.

The island of Ischia photographed from Castle Aragonese. The mountain area in the background on the island is Monte Epomeo, a resurgent dome formed as the caldera floor is lifted up above the caldera rim. Here be Dragons.

Problem here is that Monte Epomeo is a super volcano, and as such does things in super-size. And if you super-size a resurgent dome, then you have an entire caldera floor rising upwards. Just imagine the pressure needed to push up a ten kilometer wide plug 900 meters in 28 000 years.

I know, we are only talking about 3.2 millimeters per year on average, but it still requires rather stunning amounts of power. The uplift is though larger than that, the reason for that being failures in the resurgent dome with rock-slides and sector failures of the dome as it started to stick up above the caldera rim. 5 600 years ago the dome passed the rim. During the push up phase the dome had also dragged the caldera rim with it above surface, and around the island an elevated area has been created by the pressure. So, a lot of pressure has gone also into moving parts that technically are not a part of the resurgent dome.

Eruptive and other behaviors

The most common type of eruption at Ischia is smaller eruptions taking place between the resurgent dome and the caldera rim. There are quite literally hundreds of fissures, cones, and other volcanic vent types encircling the dome. These eruptions normally follow episodes of rapid surging (uplift) of the dome.

There are two more dangers on top of the island caused by the resurgent dome. The first one is quite simply sector collapses, landslides and rock-falls as the brittle welded tuff suffers structural failure. Some of these slides and rock-falls have reached as far as the coast line.

General volcanic map of Ischia showing major features of the volcano. Click for larger image.

The more dangerous version of failure is the lateral flank eruption. That happens as magma pushes upwards and builds up tremendous pressure and swelling of the side of the dome and the side of the caldera rim. Think Mount Saint Helens here and you get the picture. This causes a large pyroclastic flow going laterally over the island until it reaches the coast, then it will continue over the water. If it happens in the wrong direction it will hit inhabited land.

Critical lateral collapse of the resurgent dome towards the Bay of Naples.

During the last 12 000 years there has also been 3 sub-surface collapses of the island causing massive debris flows running out into the Tyrrhenian Sea. And there are several spots along the coast line where parts of the Island have calved off into the ocean. When this happens large tsunamis will race into the Bay of Naples destroying any part not high up. The latest known widespread tsunami in the area is known to have happened 800BC according to written records.

Debris flow from a sub surface failure of the shelf around the island. The surge direction caused a large tsunami to go into the Bay of Naples.

In the end though it is probably the super part of Monte Epomeo that interests people more than anything else. Because however you look at it, there is between 70 and 210 cubic kilometers (conservative estimate) of magma in various grades of fractionalization down under that ever uplifting plug. The volcano also has an ample supply of fresh water to drive up the pressure for a larger eruption, and when that happens the same thing that happened to Krakatoa and Santorini will happen to Ischia. And as with the two more famous volcanoes, it has happened before.

Current status of Ischia

Even though Ischia is currently not showing any sign of erupting other than the steady uplift she is deemed by INGVs Director Guido Bertolaso to be the most likely volcano to erupt due to the rapid buildup of magma that they have recorded. Bertolaso even went so far as stating “if I had to say which is the volcano with the most loaded gun barrel, I’d say it’s not Vesuvius but the island of Ischia”. He though went on to state that no eruption is imminent. This becomes evident if one looks at the lack of heightened volcanic tremor, and minimal amount of magmatic earthquakes.

Risks of Ischia

The risks are roughly discussed below in the order of likelihood. Ischia is the volcano most likely to have a large eruption in the Naples area. One should though remember that it is most likely to have a normal VEI-1 to VEI-4 eruption when it erupts next. This would mainly affect the 60 000 residents on the island, and the same amount of tourists.

Rock falls, dome failures and landslides from Monte Epomeo is also fairly likely to happen in the foreseeable future due to the resurgent dome uplifting. This will also only affect the local residents and tourists.

Large landslides either at the coast, or out on the elevated shelf that surround the island is fairly likely to happen within the next few thousand years as the pressure building up raises the land up and weakens the structure of the flanks. When this happen large tsunami waves will hit the Bay of Naples causing widespread destruction. This is also the risk that is hardest to predict and mitigate.

In the same timeframe there could be another partial dome collapse causing a Mount Saint Helens style eruption. This would destroy all buildings on the island, cook the inhabitants, and depending on the direction of the pyroclastic surge hit areas far into the Bay of Naples. I do not think we need to contemplate the effects of a hydro-magmatic eruption at the VEI-7 scale. I would only like to point out that Ischia is the most likely candidate of having such an eruption in the neighbourhood of Naples. Right now there is nothing pointing towards it happening within the next millennia, but in the end it is likely to happen within the next ten millennia due to catastrophic failure in the resurgent dome.

Ischia early in the morning. The sleeping Dragon rests calmly.

Ischia is more likely to kill people than any other volcano. This is due to the absolute lack of places to run to quickly since it is a heavily populated island, and that half of the inhabitants at any given time are tourists not knowing where to go. So even the smallest event will get messy, best case scenario is probably a VEI-1 eruption with clear precursors for INGV to order a complete evacuation. Anyhow, anything interesting happening at Ischia is more likely to kill thousands up to millions than any of it’s siblings due to it having more modes of operation.

Not only do we live in interesting times, now we have an inflamed Ischia.

Short addendum on the Turkish quake

There has been an earthquake just south Antalya. It ranged between 5.8 and 6.2, figures are going to be revised. The distance from Antalya, and depth is very likely to cause damages to houses and fatalities.

The associated beach ball has a rather odd look to it. But this is also likely to change. The EMSC-CSEM site has gone down due to pressure from people trying to get info. USGS is open for business. Here is a link to their beach ball and other technical data.

http://earthquake.usgs.gov/earthquakes/eqarchives/fm/neic_b000ac4h_fmt.php

Oddball beach ball of Turkey.

CARL

Why the VEI is Wonked

Eyjafjallajökull 2010-04-18.

The VEI scale might be the most ill-begotten piece of quasi-physics ever devised in the history of mankind. One thing becomes abundantly clear and that is that Chris Newhall and Stephen Self might be good volcanologists, but they are not in any way physicists.

Let us start with a basic problem. Eyjafjallajökull was a VEI-4 calculated on primarily the amount of tephra ejected, and secondarily on the height of the ash-plume. Grimsvötn ejected as much tephra, and had an even higher ash-plume. Both are VEI-4s according to the Volcanic Explosivity Index (VEI).

The basic requirements for a VEI-4 is that it ejects between 0.1 to 1.0 cubic kilometer of tephra, and has an ash-plume that is anywhere between 10 and 25 km high. Eyjafjallajökull ejected 0.25 cubic kilometers of tephra and had a peak ash-column of 9 kilometers. Grimsvötn is not fully tallied up, but it released the same amount of tephra in its first 24 hours, and had an ash-column that was 20 kilometers high. Eyjafjallajökull took 60 days to erupt the tephra, and only for a couple of days had a 9 km ash-column. But let us say that they both released the same amount of energy during the mentioned time spans, just for arguments sake (at least for now).

What is an explosion? It is the almost instant release of pent up energy. 1 quarter kilo stick of dynamite is the same amount of energy as 2 Mega-joules of energy, or the power equivalent of a 550 watt travelling hairdryer running for 1 hour. Guess which will blow up your car?

And here we hit the head of the VEI-nail with a stupendous physics hammer. If we go back to an explosion being your basic energy release over a specific time, then the time issue gets rather critical quickly. Why is this important? Well, the energy release over the specific time frame decides how destructive an explosion is. Dynamite is destructive, a hair dryer is not destructive (unless your stylist is a moron).

Photograph by Hrafn Óskarsson 2011. Grimsvötn seen in the evening from Reykjavik, height 20 kilometers.

Now some of you will have tallied up things and come up with a huge difference between the eruptions. If you are a normal sane person you have now calculated the difference in destructive force between Eyjafjallajökull and Grimsvötn being 60 times larger. With sane I mean that you did not study physics. To loft up the same amount of tephra in a sixtieth of the time poor Grimsvötn needed to use Eyjafjallajökulls total energy squared. This is actually simplified; Grimsvötn erupted through a 16 times wider muzzle and lofted the load to twice the height.  For those of you who own guns, you know what I am talking about. But in the end the number of 240 times more destructive will suffice. (Dear colleagues, I am simplifying things here.)

To go back to the analogue, Eyjafjallajökull was not a travelling hairdryer compared to Grimsvötn, it was more like a professional hairdryer used for half an hour. It will still though not blow up your car; it will just make your hair look un-natural quicker.

As you by now know, all VEIs are not equal, and sometimes physics is good for tearing down idiotic scales created by people who just want to have a scale named after them. When I have the time I will create a scale that actually measures how destructive an explosive eruption roughly is, but that would still not take into account all sorts of destructive forces involved in an eruption. It would just be a small component of the problem, because in the end the non-explosive Laki eruption killed more people than any other volcano in the history of mankind. VEI, yeah right! I think I will acronym my poor formulation into Destructive Index of Eruptions.

CARL

El Hierro and the art of Bad Science

The first of the phreatomagmatic explotions that was caught on a picture back when the eruption was going at a much higher rate than today. It was most likely not a real phreatomagmatic explosion, it was more likely to have been a combination together with a massive gas release. But this is what will be in store most likely for the residents of La Restinga.

After releasing the sixth missive that volcanic vent affectionately known as Bob is dead, the authorities have now finished the monitoring of the volcano.

This declaration of cessation of activity is contrary to all known data. All released data point towards that the volcanic edifice is still growing at a rate of 10 to 15 meters per 2 weeks. There is still harmonic tremor associated with new magma arriving into the volcanic system from the deep. There was a steady and visible disturbance over the volcanic vent, and the gas-measurements are still above normal readings.

Instead of happily following what is happening the authorities have decided to shut down the web cameras, discontinue active monitoring, abandoning bathymetric scans of the volcanic edifice, and generally trying to hide that there is a volcano on the island of El Hierro.

This is most likely done due to political pressure to achieve a former state of touristic bliss, since it does not have any good scientific foundation.  The responsible organizations have instead chosen to only rely on data that supports cessation, disregarding contrary factual information. This is the Popperian “Art of Bad Science”.

Only problem here is that soon Bob will be hitting the threshold of where hydro magmatic activity will be clearly visible on the surface. Something that was caught on video a couple of days ago by our commentators in here. This activity will only grow during the upcoming weeks.

In 2 to 4 weeks the authorities will most likely have a set of rather distraught residents at La Restinga as they start to see ‘rooster-tail’ explosions surfacing on top of Bob. If activities then continue we are somewhere around 14 to 20 weeks before the volcano surfaces.

Now somebody with a bit of math skill will say, “What? It grows with more than five meters per week! It should be up faster”. Not really, this is due to a cone needing more material to grow, the higher it get. So, the speed of growing in height will decrease over time.

The authorities are probably betting/hoping that the eruption will finish within the next few weeks and save their collective behinds. Sadly they will just then issue a proclamation that the volcano have “re-awakened” to save them.

I am sadly reminded of George Orwell’s 1984, where the author describes “newspeak”, where the meaning of words changes as the powers that be see fit. I never thought I would see scientists involved in the Newspeak of Volcanoes.

I feel very much for the poor residents of La Restinga that in a short time will be scared uselessly and without cause out of scientists running the errands of political buffoons.

CARL