Mt. Snowdon

View of Mount Snowdon using Googleearth by Karenz.

Snowdon is the highest mountain in Wales and an extinct volcano. The summit is easily accessible on foot, by train or you can practice your mountaineering skills there – as apparently did Sir Edmund Hillary to train for the ascent of Mt Everest. I walked it; mountaineering is not one of my skills.
Snowdon is well worth a visit as it is in a national nature reserve for rare flora and fauna.

Wales has had a marked influence on geology. Early geologists defined periods based on the names of Welsh villages. “Ordovician” is named after a Celtic tribe, the Ordovices.

Snowdon formed during the Ordovician period. It is comprised of tuff with sedimentary rocks and igneous intrusions, folded into a syncline. Around 450 ma, a caldera formed, producing ash flows of rhyolitic tuff deposits up to 500 metres (1,600 ft) thick. The current summit at 1,085 metres (3,560 ft) is near the northern edge of the caldera.

Fig 1: The Snowdon Massif (Wiki Commons, http://en.wikipedia.org/wiki/
File:North_snowdonia_panorama.jpg)

Much of Wales was under water in the Ordivician period. Wales was in a back arc basin between a subduction zone and in front of the Midland Platform. The basin had both submarine and sub aerial volcanoes. While I have focussed on the volcanic activity, there was a lot of sedimentary activity occurring as well so igneous and sedimentary rocks often form consecutive layers.

Tectonic Setting

England and Wales were part of the Avalonia micro plate; Scotland was then sited on the Laurentia plate and did not join England and Wales until much later during the Caledonian Orogeny. In the early Ordovician period, Avalonia was a volcanic arc on the northern edge of Gondwana where the Iapetus ocean crust subducted under the Gondwana plate. As the Iapetus Ocean closed, Avalonia broke off from Gondwana and moved northward to eventually meet the Laurentia and Baltica plates.
The collision of the plates resulted in the Caledonian Orogeny around 490 ma to 390 ma, the building of a chain of mountains which stretched from the Appalachians, through Snowdonia and the Lake District to Norway.

Fig 2: Caledonian/Acadian Mountain Chains (Woudloper, Wiki Commons http://en.wikipedia.org/
wiki/File:Caledonides_EN.svg))

Volcanic Activity

For Avalonia, volcanism of the Tremadoc era, c. 510 ma, was island arc, whereas the subsequent volcanism of the Llanvirn and Caradoc eras was characteristic of a back arc environment. Wales, itself, was the site of a back arc basin with voluminous calc-alkaline basaltic and rhyolitic volcanic activity which ended with the meeting of the three terranes in the late Ordovician. Acidic lavas were produced by subduction and basaltic lavas were produced by thinning of the crust of the back arc basin.

Fig 3: Profile of a Back Arc Basin and Subduction Zone (zyzzy2, Wiki Commons, http://
en.wikipedia.org/wiki/File:SubZone.jpg)

Early volcanic activity in the Tremadoc was sub aerial, followed by a period of submarine activity in the Caradoc and sub aerial again in the Ashgill.

The Snowdon Volcanic Corridor

The Snowdon volcanic corridor was built in two phases: the Llewelyn volcanic group and the Snowdon volcanic group. These are separated by sedimentary rocks.

Fig 4: Snowdon Volcanic Corridor (based on a map by Nilfanion, Wiki Commons, http://en.wikipedia.org/wiki/File:Gwynedd_UK_relief_location_map.jpg)

The Llewelyn group had five main formations: Conway – rhyolite and ash flow lavas; Foel Fras – andesitic lava and tuffs; Foel Grach – basaltic – andesitic lava; Braich Tu Du – acidic ash flow and rhyolitic tuff; and, the Capel Curig – formation of both sub aerial and submarine acidic ash flow and tuffs.

The Snowdon Volcanic Group had three centres: Llwyd Mawr – an emerging volcanic island that produced acid ash flow tuffs that were partially contained in a subsiding caldera; Snowdon, itself; and, Crafnant –deep water acidic submarine tuffs. Snowdon evolved as initial ash flow tuffs from a series of fissures south east of the volcano. The caldera subsided as more ash was erupted. This was followed by pumice and rhyolite. Ash flow tuffs were partially contained by the caldera.
Basaltic rocks also occur alongside acidic: both intrusive and extrusive basalts are found and also hyaloclastites. The sequence is acidic followed by basaltic and then a final rhyolitic phase.

At the end of the Caradoc, most volcanic activity ceased, although there were some minor eruptions later in the region. Successive orogeny episodes led to mineralisation of the faults in the region and further uplift. There are no rocks in the area that are younger than the Triassic period. Any that might have been deposited have since been eroded. Glaciation during the Cenozaic Ice Age and subsequent erosion from wind and rain formed the current landscape, revealing the underlying geology of Snowdonia.

KarenZ, 26/12/2012.

References:

http://en.wikipedia.org/wiki/Avalonia
http://en.wikipedia.org/wiki/Ordovician
http://en.wikipedia.org/wiki/Snowdonia
“British Regional Geology Wales”, M F Howells, British Geological Survey, 2007
“Geology of Snowdonia”, Matthew Bennett, The Crowood Press, 2007.

The Decade Volcano Programme

Fig.1 The dead of Herculaneum, burnt to death by 800-centigree hot pyroclastic flows from Vesuvius AD 79 (O Louis Mazzatenta, National Geographic)

The volcanic eruptions of Mount St Helens in 1980 and Nevado del Ruiz in 1985 made the general public aware of the dangers of co-existing with a large and potentially lethal volcano. It doesn’t take much imagination to see the possibilities of a lateral St Helens-type blast on a population of a great city as unaware of the hazard as the unfortunate citizens of Armero, Colombia. Blasts from the past such as Vesuvius 79 AD eruption that obliterated the large Roman cities of Pompei and Herculaneum or the 1902 eruption of Mount Pelée on Martinique, that completely destroyed the town of St Pierre, leaving only two survivors out of a population of some 22,000, served to reinforce the message. With human populations world-wide soaring, it is inevitable that humans will settle closer to potentially active volcanoes in ever-increasing densities. As a result, more human beings than ever are at risk from volcanic eruptions.

With this in mind, the HYPERLINK “http://en.wikipedia.org/wiki/International_Association_of_Volcanology_and_Chemistry_of_the_Earth%27s_Interior” \o “International Association of Volcanology and Chemistry of the Earth’s Interior”  (IAVCEI) set out to identify volcanoes that had a history of large, potentially destructive eruptions and were located close to high-density populations. As the project was initiated as part of the United Nations-sponsored International Decade for Natural Disaster Reduction, hence the name Decade Volcano, it was hoped that the United Nations would fund the programme the aims of which was to identify the major strengths and weaknesses of current hazard management and contingency plans at each volcano, and how to address the weaknesses identified.

Fig. 2 The UN General Assembly. It was ultimately here support for the Decade Volcano programme must be obtained, not at some faculty. (Marty Lederhandler, Associated Press)

It must be realised that in a highly politicised world, decisions are rarely based on scientific grounds, but on what is politically feasible. Hence the volcanoes chosen had to have a broad appeal, geopolitical as well as demographic, to the representative body that was to grant the funding. But in order to achieve at least a semblance to a scientifically motivated choice, the volcanoes chosen had to threaten tens of thousands of people with at least two of the following volcanic hazards – lava dome collapse, pyroclastic flows, lava flows, lahars, tephra fall or volcanic edifice instability. Furthermore, the volcano had to have been recently geologically active. As a sop to the UN representatives, who in turn would have to have the sanction of their masters at home, any volcano chosen had to be politically and physically accessible for study and there must also be local support for the work.

In the end, the UN did not undertake to support the programme, and funding had to be obtained elsewhere. Where there is a national body responsible for volcanologic research and monitoring such as in the USA, Italy, Mexico or Colombia, this organisation has assumed responsibility for the volcano or volcanoes that naturally fall under their aegis. The European Union supports research and monitoring at European volcanoes whereas some of its member countries, France and Germany, have undertaken to support the work of Indonesian authorities at the same time giving French and German volcanologists access to research at active volcanoes.

Fig. 3 Koryaksky volcano overlooking Petropavlovsk’s 180,000 inhabitants (Wikimedia)

The 16 volcanoes given status as Decade Volcanoes, with the (main) human habitations threatened given in brackets, are:

USA – Mount Rainier (Seattle, Washington) and Mauna Loa (Hawaii)
Japan – Sakurajima in the Aira caldera (Kagoshima and Kirishima) and Unsen (Unsen and Nagasaki)
Russia – Avachinsky and Koryaksky (Petropavlovsk, Kamchatka)
Italy – Vesuvius (Naples) and Etna (Catania)
Greece – Santorini, a.k.a. Thera (Aegean Islands)
Spain – Teide (Canaries, holiday paradise of Europe)
Mexico – Colima (Colima, Manzanillo)
Colombia – Galeras (Pasto)
Phillipines – Taal (Manilla)
Guatemala – Santa Maria/Santiaguito (Quezaltenango)
Indonesia, Java – Merapi (Yogyakarta)
Democratic Republic of Congo – Nyiragongo (Goma)
Papau New Guinea – Ulawun (???)

While no one doubts that given a possible or hypothetical worst-case scenario, these volcanoes pose a serious threat to nearby human settlements, it’s quite obvious that politics has been a main factor in their selection as Decade Volcanoes. The financially and politically influential USA, Russia and Japan have each been assigned two with four to the equally politically and economically influential Europe, while the large Hispanic contingent of nations accounts for no less than five of the sixteen.

Nevertheless, it is a start and a good one too. The programme has led to a better understanding of the volcanic hazards and in one case, at Etna in 1992, measures were taken on the advice of IAVCEI (International Association of Volcanology and Chemistry of the Earth’s Interior) that eventually prevented a lava flow from reaching a town. Scientists and civil protection authorities have learnt to cooperate as with the very nasty eruption of Merapi in 2010, without which the death toll would undoubtedly have been much higher. Awareness of volcanic hazards from volcanoes not on the list has been heightened as well. A summary of the advances and achievements brought by the first ten years of the programme can be found at “http://www.sveurop.org/gb/articles/articles/decade.htm”  Directly below, followers of this blog may be surprised, or not as the case may be, to learn that our old friend Nemesio M. Pérez compiled the final report of the IAVCEI meeting in Teneriffe, 2010.

Fig. 4 The 2334 m high Ulawun stratovolcano, Papau New Guinea (listspress)

But it cannot be claimed that all the Decade Volcanoes represent the 16 volcanic centers most dangerous to human populations, nor that the efforts are directed where they are most needed. Let us look at Ulawun, Papau New Guinea as one example! Ulawun, a 2334 meter high stratovolcano, is the tallest volcano of the Bismarck Archipelago chain and one of the most active volcanoes in Papua New Guinea. According to John Seach, it is composed of lava flows interbedded with tephra and erupts basalt and andesite through Strombolian and Pelean eruptions. Thus the main danger to humans comes from the pyroclastic flows associated with Pelean eruptions, the other Decade criteria met are those of tephra fall and structural failure. John Seach reports that the 1980 eruption resulted in an 18 km high eruption column that devastated some 20 square kilometres and claims that structural collapse could potentially lay waste to an area hundreds of square kilometres. That is an area with a radius of about eight to ten kilometres.

But is Ulawun really such a highly dangerous volcano? First of all, as far as I can tell from maps and satellite images, there are few human habitations within the danger zone. Second, it erupts basalt and andesite, neither of which are associated with particularly devastating eruptions. Basalts erupt effusively as at Hawaii or semi-explosively as at Etna. Andesites predominantly erupt explosively, but rarely result in a high VEI as both volume-wise and explositivity-wise they are small to medium. Third, Ulawun erupts regularly, 34 eruptions over the past hundred years with most assigned a VEI of 1, 2 or 3 with a single VEI 4. While this is impressive and a constant reminder to the locals that theirs is a dangerous volcano, the regular eruptions prevent the build-up of a much larger eruption – and also inhibits the build-up of a large human population on its fertile slopes.
Let’s now move our examining eye some 200 km to the NW of Ulawun! There we find Rabaul, the city of WW II fame fought over by the Japanese and Americans for its superb anchorages. Up until 1994, Rabaul was the provincial capital with a population of some 17,000 inhabitants. On September 19th 1994, the Tavurvur and Vulcan stratovolcanoes erupted simultaneously which destroyed the town as had happened previously in 1937. Fortunately, no more than five people were killed this time against 500 on the previous occasion. Today, the provincial capital has moved to Kokopo, a scant 20 km away, but Rabaul is slowly being rebuilt as happened after its 1937 destruction.

Why is Rabaul then, to borrow a phrase from Carl, such an ill-begotten piece of real estate? The reason for its superb anchorage is that it is a submerged caldera, 8 by 14 km wide. The town is located on the rim of the caldera and there are no less than eight vents of which four are stratovolcanoes such as the already named Tavurvur and Vulcan. Just to make certain of the town’s eventual destruction, the spit of land on which Rabaul is situated is not only the edge of the Rabaul caldera. A scant three kilometres due north lies the equally submerged Tavui caldera, source of the 5100 BC Raluan rhyolitic ignimbrite, an eruption listed as producing 4.0  ±  1.0  x  109 m3 of tephra.

Fig. 6 Map of the Rabaul Caldera (USGS)

No doubt there are other, and better examples of volcanoes that ought to have been Decade Volcanoes instead of some of the obviously less than well-chosen current ones, but it cannot be denied that the project has realised its goals and done so very well indeed! The context of its genesis, well before the advent of the world-wide web with its instantly accessible webcams and monitoring equipment, has to be taken into account as well. In the final analysis, the Decade Volcano programme has to be regarded as being highly successful.

HENRIK

Suggested reading:

HYPERLINKS :

http://upload.wikimedia.org/wikipedia/commons/4/42/WikiReader_Decade_Volcanoes.pdf

http://www.iavcei.org/” http://www.iavcei.org/

http://www.sveurop.org/gb/articles/articles/decade.htm

http://www.geo.mtu.edu/volcanoes/rabaul/rabaul.usgs.html

Sleeper Fish… A look at the Taal and Laguna de Bay setting.

Palawan Continental Terrane. “Palawan?” According to Google Translate, it means “Sleeper Fish.”

Sleeper gobies are members of the Eleotridae fish family, found predominantly in the tropical Indo-Pacific. There are approximately 35 genera and 150 species.

Interesting… sort of. The Palawan Continental Terrane is actually a fairly sizable chunk of material that has perplexed a few researchers as to where it came from, or how it originated. Before I yammer about that, let me point out what that word actually means… not Palawan, but “Terrane.”

A Terrane is a geologic term for a somewhat contigious block(s) of material that operate/move over geologic timescales as one unit. The boundaries are not really clear enough to call it a crust block or microplate, or microcontinent… though each of those could eventually wind up being a terrane once they get to a resting place, or are plastered onto a continent. Essentially, the material in the Terrane is related to all the other material in origin, chemical make up, and destination. Usually a Terrane originates from one crust block/plate and winds up attached to or sutured onto another. The Wrangellia Terrane is where I learned the term… that’s the region plastered to the North American craton east of where the recent Queen Charlotte quakes occurred at. If you think of bugs and windshields, you get the general idea of how terranes work and accumulate.

From the name “Palawan Continental Terrane” you would assume that it originated from some continent somewhere. According to Knittel et al., it’s a piece of the rifted margin of SE China. So where is it now? Well, it makes up a significant chunk of Mindoro in the Philippines. Mindoro is a collection of three uniquely different chunks of material. The other parts are the Philippine Mobile Belt that the Palawan Continental Terrane is sutured to, as well as a third unit that is made up of metamorphic material and a section that might indicate an ophiolitic unit… complete with gabbros. From Wikipedia: “a section of the Earth’s oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crust”

Okay… so it’s a slow motion collision in process. More correctly, part of a slow motion collision in process. Why part? Well, this affects Taal and Laguna de Bay.

Mukasa et al. points out that other researchers have pinned their origin as products of the subducting plate at the Manila trench, and then further notes that the geochemistry of them has changed as they have grown older. Specifically, they differ from the other volcanoes in the northern part of that chain. (East Bataan Lineament). The reason for this, according to the authors, is the incorporation of Palawan Continental Terrane material into the magma production.

This could explain how Taal and Laguna de Bay could have become capable of making large calderas. By its nature, continental material is more silica rich than oceanic crust. The general thought is that leading shards of this material are intruding into and being caught up in the melt formation process.

As cbus20122 notes:

…It’s amazing that such a large eruption [Pinatubo] only produced a comparative blip of a caldera when looking at the other volcanic areas on the map…

Pinatubo, being on the West Bataan Lineament, is more north and further away from this source of silica rich magma.

Right next to the Taal/Laguna de Bay region is the Macolod Corridor. From the abstract of a pay to play paper by Förster et al (1990):

an approximately 40 km wide zone of still active intense Quarternary volcanism which perpendicularly crosses the Island in a NE-SW direction … we believe that the corridor is a pull-apart zone formed by a diffuse system of NW-SE oriented shearing.

And of course… a plot of sorts. Not my usual, I wanted to focus on quake depths in relation to the major players. This was put together with DivaGIS. Red Quakes are greater than 90 km deep, Blue quakes are less than 90 km deep. Somewhere around 125 km is where melt percolates off of the subducting slab. The majority of the deep spike is under and just to the southwest of the Taal parent caldera. (The one the island of Taal sits in). There are a few deep quakes up around Pinatubo, but nothing like the area around Taal. These are quakes from the USGS list back to 1975 and greater than magnitude 4.5 or so.

GEOLURKING

An after the fact addition: If you note my first graphic, there is a region that forms a “T” with the Manilla Trench that I called “Old South China Sea Spreading Center.” A closer look at this was done in “Basement structures from satellite-derived gravity field: South China Sea ridge” by Braitenberg et al (2005). You may find it of interest. It is what put the Palawan Continental Terrane where it is.

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“The Macolod Corridor: A rift crossing the Philippine island arc” Förster et al (1990).

“The Nd-, Sr- and Pb-isotopic character of lavas from Taal, Laguna de Bay and Arayat volcanoes, southwestern Luzon, Philippines: implications for arc magma petrogenesis” Mukasa et al (1993)

“Permian arc magmatism in Mindoro, the Philippines: An early Indosinian event in the Palawan Continental Terrane” Knittel et al (2009)

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UPDATE:
NAME THAT VOLCANO RIDDLE by Suzie!

The prime minister and the volcanologist were having a heated debate about health and safety issues.

”You are grossly over estimating the danger” shouted AP in frustration.
”Yes its active but it has not erupted for a few thousand years, and the local fishing community, who admittedly get a bit confused about their birthdays, stay safe by holding hands!”

”Ahhhh but you are forgetting something important” retorted BP immediately ”smoking kills!”
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ALAN`S EVIL RIDDLE
Years ago Friday, Her Serene Highness may have worn this green coat under the stars!

1) What am I?
2) My composition and uses?
3) Which constellation could be related to a cousin?
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Suzie will do her own Dinging and i will do it for Alan.
Happy riddling Spica

Volcanic Riddles for the Crowd!

Hello everyone!

After a very volcanically unhectic week it will be good to bend the heads over two mind-contorting riddles. I had prepaired a Name that Volcano Riddle, but then Suzie sent me one that was so mind-boggling that I felt like a understudy Riddler.

There is also another instalment of Evil Alan’s mineralogical riddles. This time Alan confesses to his favourite movie.

About the video, a couple of posts ago I wrote about Volcanologists and Geologists playing Lip Banjo. It comes from a geologist friend of mine who described the joy of when he found a brand spanking new mine in Sweden as “Doing splits while playing Lip Banjo”. I got a lot of comments and a couple of emails where people seriously asked how you play Lip Banjo, so, up above is an instructional video for how Volcanologists play Lip Banjo.

Name that Volcano Riddle by Suzie

 2012582 Who am I?

Here are 4 picture clues.

Clue number 1

Clue number 2

Clue number 3

Clue number 4

Evil Alan’s Riddles

I sound as if I should have some connection to Dundee! Mmm, whilst I won’t do you any good, a relative is good on ice!

What am I? To what are the good and bad referring? (3 points to be had)

Good luck everyone!

Update!

Since everyone seems to have gotten sad that the Riddles are riddled out, here is a bonus riddle.

‘Finnish shemale fish, under what watery grave do I rest?’
Name the Volcano, and name the watery grave. 2 points.

CARL

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