Eifel Volcanic Field II

Recently Nathan took you on a comfortable journey into the Eifel volcanic field. But what is the origin of this intraplate volcanism and where will the journey go?

About 400 million years ago during the Devonian, the Age of Fish, when only plants and insects roamed the land, Laurussia and Gondwana converged into the supercontinent of Pangaea forming the European Variscan Belt. It includes vast mountain ranges stretching from Portugal to Turkey. The Rhenish Massif in central Europe is one of the outcrops of this period, others are the Massif Central in France or the Bohemian Massif in Czech Republic and Poland.

The Rhenish Massif is mainly made of highly folded sedimentary metamorphic rocks, mostly slates, hence the name “Rheinisches Schiefergebirge” or “Rhenish Slate Range”.

Geological map of the Rhenish Massif. Author Jo Weber (Wikimedia Commons)

When the Age of the Mammals dawned and Africa started to collide with Eurasia, a whole lot of volcanic activity started north of the rising Alps. This belt was termed European Cenozoic Volcanic Province by Meyer and Foulger. In the Alpine forelands extensional rift systems developed with the Rhine graben as a prominent feature. Volcanic activity of that period can be found in France (Massif Central), Germany (High Eifel, Westerwald, Vogelsberg, Rhön), The Czech Republic (Eger graben) and Poland (Lower Silesia).

Figure 1 from Meyer and Foulger http://www.mantleplumes.org/Europe.html

The ductile and tough shale and slate bedrock of the Rhenish Massif presumably was incompatible with extensional rifting. Instead the region acted as a hinge between shear rifting along the Upper Rhine Graben and extensional rifting at the Lower Rhine Basin (Illies et al. 1981).

Tectonic situation in central Europe (from this thesis, modified from Illies and Fuchs, 1983)

The Eifel volcanic field is situated west of the Rhine river near Koblenz in the center of the Rhenish Massif. Fluvial deposits prove that this area was uplifted up to 300 m since the Pliocene epoch 5 million years ago and that the uplift had accelerated during the last 800,000 years with maximal elevation around the Eifel volcanic field. Since then the Rhine river and its tributaries were forced to cut deep valleys through the Rhenish Massif, flowing past Hunsrück and Taunus, Eifel and Westerwald, Ardennes and Süder Uplands.

Uplift in the Rhenish Massif, from Meyer and Stets (2002)

The most recent volcanic activity in the West and East Eifel volcanic fields coincides with this uplift which amounts to 0.35 mm per year on average. The dome building may be a combination of widespread uplift of the so-called Rhenish Shield due to horizontal deformation from Alpine orogeny (Illies et al., 1979 and 1981; Meyer and Stets, 2002) and more locally by uplift due to the Eifel mantle plume (Schmincke, 2007).

To study the deep structures of the Eifel region the Eifel Plume project temporarily deployed a large network of seismic stations in 1997. A shear wave velocity model suggested a 100 km wide low-velocity structure extending down at least 400 km into the upper mantle which could indicate an area of increased temperature and partial melting. It remains debated whether this anomaly caused the Eifel volcanism. Other volcanic areas of the European Cenozoic Volcanic Province lack clear evidence of deep mantle plumes and the spacial distribution and timing of eruptive phases is not consistent with movement of the European plate over a fixed hot spot.

Alternative models could be a magma source derived from previous Alpine subduction or local decompression melting from passive rifting caused by tectonic deformation of the crust. Notably, the Mohorovičić discontinuity (Moho) is only 30 km deep below the Eifel while under the Alps it goes down to about 50 km which could give rise to some mantle turbulence and convection.

South-North section of the Moho beneath Europe between 6 and 9° longitude. Depth is highly exaggerated (Image by chryphia). Data from www.seismo.helsinki.fi/mohomap/

There is an overwhelming amount of literature about the recent quaternary activity of the 300+ volcanoes in the Eifel, sadly most of it paywalled or even without online access, because published in books or exotic German journals. So the following is taken from secondary literature. The eruptive history was e.g. summarized by Schmincke in Mantle Plumes (2007), Schmitt et al. (2010) (see Fig. 1 here for a map of geological map of the East Eifel volcanic field) and is nicely illustrated in this German blog post.

In summary, there seem to have been at least four main eruptive phases:

700,000 to 450,000 years before present: the main bulk of monogenetic volcanoes, small cinder cones and short lava flows erupted in the West Eifel and late some in the East Eifel. Their lava contained leucite (potassium rich) basalts, poor in SiO₂, indicating an upper mantle source.

The West Eifel then fell dormant for several hundred thousand years.

430,000 to 360,000 years before present: In the East Eifel the Rieden complex (“Riedener Kessel”) west of the Laacher See had its most productive episode sputtering out several cubic km of lava in larger cinder cones and kilometer long phonolithic lava flows out of a 4 km diameter caldera system.

215,000 to 190,000 years before present: In the East Eifel the Wehr volcano (“Wehrer Kessel”, a 2 km diameter depression) west of the Laacher See and many large scoria cones in the Neuwieder tectonic basin erupted several cubic km of dense rock equivalent. The lava was highly differentiated phonolitic and rich in SiO₂, indicating that country rock had been partially melted. During this time the first Maars were blasted out of the West Eifel volcanic field.

100,000 to 10,000 years before present: the West Eifel field was peppered with Maars still erupting the original lava, the last one to be the Ulmener Maar. Simultaneously, a new kind of lava, basanites, poor in potassium, hence leucite free, presumably from the asthenosphere, created large cinder cones and lava flows sometimes right next to the Maars (e.g. Meerfelder Maar next to the Mosenberg).

In the East Eifel only the Laacher See erupted 12,900 years ago, without doubt the most powerful eruption of all time in the Eifel probably equalling the total output of the West Eifel volcanic field. The Laacher See erupted more than 6 cubic km of magma within days, with an at least 25 km high eruptive column spreading tephra from Italy to Sweden. The magma is thought to have differentiated over several thousand, possibly tens of thousands of years, showing zonation from mafic to evolved phonolite and carbonatite. Pyroclastic flows temporarily built a dam in the Rhine river which eventually broke unleashing torrential floods, illustrated here (in German). Finally the emptied magma chamber collapsed leaving this recreational lake.

The “Loch Lochy” of Germany, the Laacher See. Image by USEBlackbird (Wikimedia Commons)

So the Eifel volcanism occurred in tens to hundred thousand years periods intermitted by hundred thousand years of dormancy. There was a general trend of eruptions starting in the NW progressing to the SE. Eruptions became increasingly voluminous and explosive with time and there was a shift of lava from an upper mantle source to partially melted crust.

Today the Eifel volcanism is dormant. As already featured in Nathan´s post abundant CO₂ emission is a sign that the Eifel volcanic field is not extinct. But also seismically the region is active. Earthquakes during the past 36 years are almost exclusively confined to the upper 15 km. There is no indication of magmatic origin so far. The highest earthquake density is east of the Laacher See and west of the Neuwieder basin along the Ochtendunger fault zone on a NW to SE axis, aligned to the general tectonic setting in the Rhenish Massif.

Recent earthquakes (Sep 2012 to Jan 2013, green, enlarged) and earthquakes dating back 36 years recorded by the seismic station Bensberg, University of Cologne. Image by chryphia.

And here a 3D plot:

Since 1975 up until January 2013 over 1180 local earthquakes were reported by the seismic station Bensberg (University of Cologne) with some increased frequency in the last years.

Earthquake data from the seismic station Bensberg from 1975 to 2013 (between 5.21 and 5.472° lat and 7.25 and 7.65° lon, as in 3D plot). Image by chryphia

Helium and other noble gases that are found in high concentrations around the Laacher See are indicators of the volcanic origin of the Mofettas. Helium isotope 4 (⁴He) is naturally formed in earth´s crust. Another rare Helium isotope, Helium 3 (³He), is produced by fission and bombardement with high-energy cosmic rays, so what we find on earth was created before our solar system formed. In the atmosphere it escapes into space. Looking at the ³He to ⁴He ratio in volcanic gases relative to the ratio in earth´s atmosphere (Ra) gives a clue about the source of the magma. If it´s of deep origin, it still should contain relatively high ³He. The ³He/⁴He ratio measured from Mofettas from the Laacher See is 5.5 Ra, indicating an upper mantle source, but it is less than measured at mid oceanic ridges (8 Ra), thus there is mixing with ⁴He from the crust.

So there we are today. Was this the end of it for the next 100,000 years? As long as the Brubbel squirts and the earth rumbles occasionally we can´t be sure of it. Maybe the ants will tell us one day.

And just in case: a list of webcams

chryphia

Many thanks to Nathan for discussion and support!

Ruminerian V – Get your coffee, you’re gonna need it.

One of the reasons I do this, is because as I was growing up, having an interest in things Geophysical/Astrophysical, there was always a search for the “wow” factor. Not everyone’s “wow” sense is geared the same… and in some cases, the scale of stuff that people are familiar with has a lot to say about how they perceive the “wowness” of it. Grabbing that meaningful nugget of data, or of a concept that totally re-vamps your experience level is way cool. It changes your world in incremental steps… or at least how you look at it.

The difficult thing is finding usable data to ruminate on, or to have some esoteric thought wrapped up in equally esoteric language. (see “e-folding” from the last Ruminerian) It’s not that people are intentionally obtuse with the language or ideas, it’s that there is a lot of technical jargon that develops out of any technical field. (How many of you know that a “gyraline modulator” is?) This post, and the others that I have written, are geared towards the person who seeks to find out more.

This, is more.

Before I continue, a bit about SO2. SO2, Sulfur Dioxide, is a volcanic gas. It reacts with water to form H2SO4, also known as sulfuric acid. Take away the water and you get sulfate, SO4. The reaction in the atmosphere goes something like this:

SO2 1 OH 1 3H2O ═> H2SO4 (1) 1 HO2

In Ruminerian IV, I ended on a pretty interesting graphic. (well, I thought it was)

It is derived from “Stratospheric Loading of Sulfur from Explosive Volcanic Eruptions” Bluth et al (1997). This plot shows the e-folding times for SO2 to sulfate conversation, and then for sulfate removal from the stratosphere.

Where this particular model fails horribly, is in how it treats the SO2 input. It assumes one sizable lump of SO2 injected to the stratosphere. Odds are that many volcanic eruptions are not going to be just one quick blast of SO2 and the show is over. For the sake of modeling influx to the stratosphere, you can probably get away with it… but you have to always be aware that this ideal treatment is going to be incomplete. Another line of thinking is that an established vertical plume can eventually propel the gases past the tropopause if it persists long enough and has enough strength.

Revising that plot and looking at the peaks in it and the narrative that went along with it, moderate sized SO2 releases have a sulfate peak about 2.07 months after the event. In winter (for whatever hemisphere) this conversion rate can be slowed by up to 20% (Bluth et al 1997) giving a peak at about 2.27 months. (30 day months). For large eruptions the curves yield 2.78 months and 2.99 months (winter).

Okay, a lot of stuff about … something. But why?

Sulfate is an aerosol. “a suspension of fine solid particles or liquid droplets in a gas.” Smoke from a fire is an aerosol. Clouds and fog are aerosols. That brown crud drifting off of the iron pellet plant in Bahrain is an aerosol. That massive black cloud that spurted out of the stacks on a steam powered Cruiser in Mayport Florida, that then settled on the Quarterdeck of the spiffy new Gas Turbine powered Cruiser moored on the other pier… that was an aerosol. (trashed a lot of summer white uniforms as the partially burnt diesel precipitated out) Even that gunky haze that you can see over New York from 30 km at sea is an aerosol (the same for LA by the way). Fine particles suspended in a gas.

In some way form or fashion, they all act upon light that is traveling through them. Reflection, scattering, refraction, absorption. You name it. If the particles are quite small, the effects are generally in the category or Rayleigh scattering. That’s what makes those vivid sunsets or the sky blue. If they are about the size of the light’s wavelength, you get Mie scattering. That’s the effect that makes the clouds appear white.

Now I deviate. As I was growing up, I used to listen to the radio. At night I could pull in stations from hundreds of miles away… during the day time, only the closer stations would show up. I had a great uncle who was into Ham radio, and he took a partial interest in my fascination with all things electric. He gave me a copy of an ARRL handbook. I never got a ham license, but I learned everything in that book… and then some. (I wound up specializing in Electronic Warfare in the military). That late night effect that allowed me to hear stations far away, is caused by ionized layers of the atmosphere.. specifically, the ionosphere.

There are three principle layers involved, the D layer which is strongest during the day, mainly absorbs radio waves. Above that, the E layer, present during the day, acts to reflect radio waves. And above that, the F layer. It’s always present, and in the day time it tends to split into the F1 and F2 layers. This is the one that causes most of your long haul radio intercepts late at night. In CB jargon, its called “skip” because that is what the signal is doing… bouncing off of the ionosphere, back to Earth, and could bounce a second time repeating the process. (no, this is not the Van Allen radiation belts, that is something totally different) “Anomalous propagation” (the real term) can occur due to a number of causes… the sun is the main driver, but meteor showers can energize the various layers also.

This rather busy plot gives you an idea of where everything is at. Note that the vertical scale is logarithmic. Just for reference, I’ve place a few altitude events and items in there for reference… such as Felix Baumgartner’s leap altitude, and the record holder prior to that, Joseph Kittinger. Also noted are high and low altitude of the ISS, and the elevation that Mt Pinatubo erupted to during it’s strongest phase.

Now for something totally new to me. Christian Junge, Atmospheric research pioneer, released a paper in 1961 announcing he discovery of the stratospheric aerosol layer. This region is the area where the nitty gritty happens with respect to volcanoes and the climate. I have spent a few days tracking down good info on the location and the make up of the Junge layer plus some of what goes on there.

It resides at about 17 to 30 km in altitude, depending on conditions. This layer is where sulfate occurs when it forms. How dense it is depends on a number of factors… one of the strongest factors is volcanic activity. A volcano can load this layer quite quickly, and as you saw from the e-fold plot, the material can stick around for a while. One interesting thing that I found out was that the Junge layer can occur at distinct elevation nodes. During heavy volcanic activity, there can be an upper and lower node. Eventually it all settles to that lower range over a period of several months.

Yet another interesting thing about it, is that it is usually there… whether the volcanoes are running or not. There is always a background level of sulfate. This is where it gets pretty wild.

At one time, it was thought that SO2 in the atmosphere (troposphere) could drift up and cause this persistent layer. With the way SO2 plagued Los Angeles, you can bet your bottom dollar that some people were chomping at the bit to blame modern society. Many of us have sat around the Café or over at Eruptions or Jon’s Blog oogleing the OMI or TOMS SO2 vertical column data. Some of the plumes we have seen are valid volcanic events, many are not. Beijing almost always has a plume drifting out over the Pacific, one plume that was seen was slap dab in the middle of nowhere… until we found an industrial facility in the Northern reaches of Russia. (Siberian Traps fans were enthralled at possible implications) Of course Europe and The US are producers… even with the emissions standards. Couple those with the bona-fide plumes we have seen, Tolbachik, Grímsvötn (for some reason a huge plume formed over Iceland two weeks after the eruption), Puyehue-Cordón Caulle … you would think that there would be a huge effect in the Sulfate formation.

It’s not gonna happen. At least not from SO2. (Note, Grímsvötn easily punched the tropopause with it’s eruption, I’m referring to the later plume.)

SO2 is a highly reactive gas. As you can see from that plot that it only takes about two and half months for it to react out to below about 10% of what was emitted. (and that’s at the stratospheres rates, it’s probably faster in the tropopause where water vapor is quite abundant) SO2 just does not have the staying power to wind up in the stratosphere due to riding the air currents. In fact, some researchers have studied the SO2 concentration vs altitude and come up with something like this:

Don’t be fooled by that really high correlation coefficient. That’s just how well the curve fit an averaged set of multiple curves generated from the data in Meixner (1984). Think of it as a general guideline and nothing more. What is important is that SO2 trails off quite rapidly with height. It just doesn’t have the staying power.

Before I press on I would like to make mention that the Atmosphere is a highly complex dynamic system. We know a few things about it, such as large scale circulation patterns, but with as much as we do know, you can bet your bottom dollar there is just as much if not more, that is not known. Here is a tidbit that most people don’t know.

Notice the red up arrows. These are the regions where low pressure systems dominate. As air rises, the surrounding air flows inward to fill the space. Where the blue down arrows are at, high pressure systems dominate. Overall horizontal circulation of the individual lows and highs is driven by the Coriolis effect … which is due to residual angular momentum from where the air is coming from. In the Northern hemisphere, Lows rotate clockwise, highs counter clockwise (as viewed from the top). In the Southern Hemisphere, the reverse applies.

Across the world, there are regions that have what are known as “semi-permanent” features… the Icelandic Low is one, another is the Bermuda/Azores high (depending on where it happens to be at) There is no hard and fast rule about what latitude something is going to be at, this is just a generalized rendition of where the boundary regions are at.
Notice that not only is the tropopause usually low over Iceland… the general circulation pattern is lofting air to the tropopause. This also applies to the Kamchatka peninsula which is also not too far south of the Polar cell boundary. (The same for the Aleutian island volcanoes)

Now we move on to the reason for the post… (hell of a lead in eh?)
Two of the more significant volcanic eruption styles… are the massive VEI-6+ explosive eruptions… and the not so explosive VEI-6+ flood basalt events. Of the two, one would think that the huge lava flow events wouldn’t have much of an opportunity to loft stuff above the tropopause. We have already seen that SO2 doesn’t have much staying power, and tends to be scavenged out pretty quickly in the area where most of the water vapor is at… down here in our little realm of existence in the troposphere.

Yet there is a way that massive flood basalts can easily contribute to the Stratospheric Aerosol Layer (another name commonly used for the Junge layer.)

It comes in the form of a little molecule called Carbonyl Sulfide. OCS.
Carbonyl Sulfide can be considered as an intermediate between CO2 (carbon dioxide) and CS2 (carbon disulfide). It has a really long persistence in the troposphere… accounting for up to 80% of the sulfur gases present. I’ve seen residence times ranging from 4 years, to 7.1 to 11 years. Basically, it doesn’t like to react. This gives it time to wander throughout the different atmospheric flows and become well distributed. And a really interesting thing happens when it is hit with ultraviolet light of about 200 to 270 angstroms. (UV-C). The bonds begin to break and it dissociates. Once it does that it forms CO2 and S2… the S2 then reacting with the H2O and OH radicals forming H2SO4… the sulfate.

Hello aerosol haze.

Okay… we have a mechanism not involving SO2 that can make sulfate. Some of the largest sources are the oceans, fossil fuel usage, even the making of concrete. (via a catalytic reaction). In general, the background level of the aerosol is not that big of a deal unless something radically increases the amount there… like an large explosive volcano. Or, a really big flood basalt event. (Eldga, Skaftar, Krafla, Þjórsá lava or any of the huge flow fields that pop up in Iceland from time to time)
Remember, OCS is ultra stable in the troposphere, but once it gets to the stratosphere where the UV-C can get at it, hello Aerosol Haze.

Enjoy!
GEOLURKING

This article has gone through about 4 revisions before I actually wrote it. I hope you were able to read it without dozing off. If you did, it’s no big deal. I doze off reading what I think is really interesting stuff from time to time.

Note: The energy in a photon packet (or wave packet depending on how you look at it) is determined by it’s wavelength. The shorter the wavelength, the more energy per packet. 200 and 270 angstroms are the wavelengths that OCS best dissociated at when exposed to it. I don’t know why, but the ratio of the length of the two bonds is pretty close to the ratio of the differences in those two wavelengths. It’s about 1731 times the length of the bond in both cases. Why? I don’t know. I just found it interesting.

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As noted there were about four iterations of this post before I actually wrote it. Here is some stuff didn’t make it in, but deserves to be mentioned. (well, since I already did the plots for it)

Stepping back from Carbonyl Sulfide… and back to Sulfur Dioxide and the usual way that volcanoes can affect the Junge layer. NASA GISS has a few models they play with. One is a compilation of the “Stratospheric Aerosol Optical Thickness” (What they have against Christian Junge is beyond me, the Junge layer is where most of this stuff is at.) One of the data products is something called the “Tau Line” and represents the average thickness at 550 nm. (that’s pretty much in the middle of “green” light at 520–570 nm.)

http://data.giss.nasa.gov/modelforce/strataer/

For those of you who are chomping at the bit over the Roaring 40′s, nothing really shows up, but they have some nice graphic of sulfate blooms and spreads for various volcanoes over the years. They also have that tau line data set.

First, let’s look at some of the more recent party poppers.

This is a plot of the Tau Line (Aerosol Optical Depth) in relation to a few volcanoes that have gone off recently. Notice that the hemisphere that received the brunt of the sulfate load depends on what volcano erupted.

Also notice that the shape of the curve pretty much follows the decay rate. The lag time between the eruption and the sulfate peak is noted. For the most part, it follows the growth and decay curves at the beginning of the post. Personally, I thought that was pretty neat.

So.. how do they compare to some known atmosphere shakers? Volcanoes such as El Chichón or Pinatubo?

El Chichón, at 17.36°N, had most of it’s effect in the Northern Hemisphere. According to Wikipedia, the Mauna Loa observatory registered a larger drop in Solar radiation transmittance than Pinatubo. However, Pinatubo (15.14°N) had a longer duration of it’s drop. It also had better coupling to both hemispheres. It also had 4.8 times the output of bulk tephra (using GVP Data).

Comparing them with those diminutive spikes over at the right hand side of the plot… those are the ones shown in the previous plot.

How is that for perspective?

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Analyses and visualizations used in this [study/paper/presentation] were produced with the Giovanni online data system, developed and maintained by the NASA GES DISC. (Specifically, the tropopause elevation data)

http://disc.sci.gsfc.nasa.gov/giovanni/overview/index.html#maincontent

“Stratospheric Loading of Sulfur from Explosive Volcanic Eruptions” Bluth et al (1997)

http://www.geo.mtu.edu/~raman/papers/BluthJG.pdf

“The role of carbonyl sulphide as a source of stratospheric sulphate aerosol and its impact on climate” Brühl et al (2012)

http://www.atmos-chem-phys.net/12/1239/2012/acp-12-1239-2012.html

“The Vertical Sulfur Dioxide Distribution at the Tropopause Level” Meixner (1984)

http://link.springer.com/article/10.1007%2FBF00114130?LI=true#page-1

“A ThreeDimensional Global Model Study of Carbonyl Sulfide in the Troposphere and the Lower Stratosphere” Kjellström (1998)

http://link.springer.com/article/10.1023%2FA%3A1005976511096?LI=true#page-1

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