The Trans-Mexico Volcanic Belt, Cotopaxi & Sakurajima

The extreme southern end of the North American Plate where it slides over the Cocos and Rivera plates. The extreme end is made up of at least seven terranes” or pieces of crust that have been joined together into one larger heterogenous bloc. GMP is the abbreviation for the Guerrero-Morelos platform. (Modified from Ferrari et al 2012)

The extreme southern end of the North American Plate where it slides over the Cocos and Rivera plates. The extreme end is made up of at least seven terranes” or pieces of crust that have been joined together into one larger heterogenous bloc. GMP is the abbreviation for the Guerrero-Morelos platform. (Modified from Ferrari et al 2012)

The latest article really did invite a sequel as the short time at my disposal and the dearth of publicly available material led to it not being on as solid scientific foundation as we like them to be. This will be set right now. Early this week there was a letter in my mail, physical as opposed to electronic, which upon opening revealed an absolute gem of paper on the TMVB. Unfortunately like so much these days, the full version of which I received a print-out is hidden behind a paywall.

A good starting point for a closer view on the tectonics of Mexico and Central America is the Chixchlub impact 65 million years ago. Although some may not credit this with much of an impact on the geology of today, it is well to remember that a simultaneous and similarly-sized impact in the Indian Ocean is credited with causing the Deccan Traps Large Igneous Province eruption and that at 250 MY, a greater impact variously believed to be hidden in the Indian Ocean near Reunion or under the Antartic Ice Sheet caused Gondwanaland to split asunder and separated what now are Africa, South America, Antarctica and Australia from each other. An impactor 10 – 15 km in diameter travelling at ~25 km a second carries such an enormous amount of kinetic energy that it makes a mockery of the efforts of even the thickest of cratons to resist it. Whichever plate was hit would have been punched through completely and at the very least fractured if not broken up into fragments.

Today, the Trans-Mexico Volcanic Belt, TMVB, the southernmost portion of the North America Plate, overlies the Riviera Plate to the west and the Cocos Plate to the south-south west. This portion itself is made up of at least seven terranes, smaller pieces of continental crust welded together. The paper begins by describing the mainly rhyolitic volcanism during the period between approximately 40 – 34 MY BP. In the NDVP article, I mentioned the Tilzapotla Caldera located about 100 km south of Mexico City but this paper makes it clear that it occurred in the “Guerrero-Morelos platform” terrane and has nothing to do with the TMVB, except bordering to it.

The approximate crustal thickness in the vicinity of Mexico City. The TMVB is rendered in beige, some of the volcanic features have been marked in blue, Nevado de Toluca and Popcatépetl with fat crosses and the Chichinautzin volcanic field circled. Instead of occurring at or near the edges, volcanism seems to have burned through the craton where it is at its thickest. Adapted from Ferrari et al 2012, based on the original MARS analysis by Steve Grand.

The approximate crustal thickness in the vicinity of Mexico City. The TMVB is rendered in beige, some of the volcanic features have been marked in blue, Nevado de Toluca and Popcatépetl with fat crosses and the Chichinautzin volcanic field circled. Instead of occurring at or near the edges, volcanism seems to have burned through the craton where it is at its thickest. Adapted from Ferrari et al 2012, based on the original MARS analysis by Steve Grand.

About seven million years ago, the Trans-Mexico Volcanic belt began to form when the underlying and subducting Cocos Plate detached from the bottom of the Mexico City craton at the northern part of its main thickness. Before this, the Benizoff Zone of dehydration which drives Arc volcanism was located just to the north of the TMVB and is the cause for the arc of ancient volcanic features that runs along the northern edge of today’s TMVB. Incidentally, almost all identified calderas in the TMVB lie near this old volcanic arc, just to the south of it. Also, they are clustered in the eastern half, above the Mexico City craton and not the western Guadalajara one.

A cross-section of the Mexico through the Sierra de Nevado volcanic range. Crust is in orange, the N-S section of the TMVB is rendered in yellow, the present-day position of the subducting plate is in brown with its approximate position at the time of detachment at ~7 MY in purple. Adapted by the author from Pérez-Campos et al 2008.

A cross-section of the Mexico through the Sierra de Nevado volcanic range. Crust is in orange, the N-S section of the TMVB is rendered in yellow, the present-day position of the subducting plate is in brown with its approximate position at the time of detachment at ~7 MY in purple. Adapted by the author from Pérez-Campos et al 2008.

After detaching about 7 MY, the subducting slab began to bend downwards which resulted in the creation of the Mexico City and Toluca basins as well as the volcanism of the TMVB. The angle at which the subdacting plate disappears is ~20 degrees from the perpendicular, which could explain how it was energetic enough to burn through the thickest part of the continental craton. Ferrari et al claim that the dehydration zone “lies at a depth of 40 – 100 km”. This is unclear as it would place it inside the Mexico City craton. Most likely, they meant that it lies 40 – 100 km below the craton, something which would place it at a depth of about 90 – 150 km below the surface which would be consistent with findings elsewhere.

There you have it. This is “our Beast”, an unusually steeply inclined subduction zone which concentrates the energy until it was sufficient to burn through a continental craton up to 55 km thick. It is not unique, there are places such as Etna where a thin slice of the subducting slab has been bent backwards but here in Mexico, it seems to be uniformly over a large area.

A final note on the Chichinautzin Volcanic Field just south of Mexico City. Piecing together the information from several papers reveals an unusual feature or sequence of events. The latest eruption in the CVF was from the 340 AD eruption of the Xitle scoria cone. Not only do the lava flows from this eruption reach far inside modern Mexico City, they also partially buried the highest peak of the CVF; Volcán Ajusco. The paper on the Xitle eruption calls Volcán Ajusco “a lava-dome complex” whereas others unequivocally identify it as a stratovolcano. If the latter is true, we have the highly unusual situation of a volcanic field being in the process of burying a stratovolcano. The CVF does indeed merit further studies as does the entire TMVB, something Ferrari et al point out in their “Concluding Remarks” – “Several aspects of the TMVB however are still unclear and constitute opportunities for future research.” Their paper is definitely very rewarding for those who manage to get hold of it.

Cotopaxi

Cotopaxi August 2015 and Eyjafjallajökull April 2010. If we can make allowances for the great difference in size between the two volcanoes, there are some striking similarities on offer here. (Composite of IG-EPN webcam capture and unknown)

Cotopaxi August 2015 and Eyjafjallajökull April 2010. If we can make allowances for the great difference in size and morphology between the two volcanoes, there are some striking similarities on offer here. (Composite of IG-EPN webcam capture and unknown)

Although one can never take the behaviour of one volcano as proof that another will behave in exactly the same manner, the similarities do lead to some conclusions. First of all, make note of how the relative small eruption plume from the crater is dwarfed by what happens once the hot magma hits glacier snow and picks up energy. This is a phenomenon also seen occasionally at Etna. It identifies the eruption type as Strombolian and the magma as most likely basaltic-andesitic in composition.

As we have magma erupting, and has been for the best part of a week, the vent is now open and the likelihood of a large explosive eruption has diminished. Although a larger eruption cannot be entirely ruled out, it seems likely that Cotopaxi will continue in this vein for some time to come and the longer it does so, the better it is. This gives the glaciers time to melt slowly and in small increments, something that would greatly reduce the risk for devastating lahars. Caveat: With volcanoes, you can never take anything for granted. If you are a local reading this or someone planning a visit in the near future, remember! This is an amateur blog. For accurate information and updates, please visit the Instituto Geofisico website at
http://www.igepn.edu.ec/

Sakurajima

An aerial reconnaissance flight photo of the Showa Crater taken on August 19th (Mahito Kaii)

An aerial reconnaissance flight photo of the Showa Crater taken on August 19th (Mahito Kaii)

Yesterday, the JMA confirmed that the Showa Crater has been blocked up and that as a result of this, pressure is increasing according to Masato Iguchi (Director of the Kyoto University’s Sakurajima Volcano Research Center). With predictions for a large eruption floating about the Internet, a few facts might be well to keep in mind. The total amount of uplift this year is 16 cm, a figure that should always be doubled as magma pushes down as well. Uplift is also clearly limited to the volcanic island itself. When Eyjafjallajökull erupted in 2010, the maximum uplift inferred was about 75 cm and the area uplifted had a radius of some 20-25 km, vastly greater than the current crisis at Sakurajima. Yet for all that, Eyjafjallajökull erupted no more than ~0.140 cubic km over a couple of months.

A 3D-rendering of the uplift at Sakurajima over the past eight Months. The uplift totals 16 cm and is very much centered on the now blocked Showa crater. (JAXA)

A 3D-rendering of the uplift at Sakurajima over the past eight Months. The uplift totals 16 cm and is very much centered on the now blocked Showa crater. (JAXA)

However, Sakurajima is located at the centre of the Aira Caldera and there has been steady uplift elsewhere for years. I have not seen any news that this uplift too has increased, which could mean that the caldera was becoming active or “restless”. Nor has there been any news that there has been a sudden drop, something which could indicate that magma from other parts of the caldera are being fed into Sakurajima. The evidence this far points to the crisis involving Sakurajima volcano and the Showa crater. The amount of uplift would indicate a possible explosive VEI 2 or possibly low VEI 3, something that would be very serious but probably not devastatingly catastrophic. However, with the Showa crater blocked, magma could force its way to the surface through another vent which could be the reason behind the JMA report on August 15th of an increase in the frequency of volcanic earthquakes detected under Minami-Dake Crater accompanied by rapid inflation which was what prompted the JMA to raise the status to Alert Level 4.

Finally, a couple of personal notes. For reasons private and undisclosed, Carl has been unable to take an active part for the past couple of months. Also, there are some issues relating to my personal health which unfortunately mean that I cannot pick up the slack even if I did take over one of Carl’s NDVP posts. This means that new posts will be “as when” and not the regular twice a week we had initially had aimed for. But there is always room for Guest posts and should you feel so inclined, please do not hesitate to contact us via our Gmail account!

Henrik

 

Luca Ferrari, Teresa Orozco-Esquivel, Vlad Manea, Marina Manea, “The dynamic history of the Trans-Mexican Volcanic Belt and the Mexico subduction zone”, Tectonophysics 522-3 (2012)

53 thoughts on “The Trans-Mexico Volcanic Belt, Cotopaxi & Sakurajima

  1. Many thanks for the follow-up.

    For All: As usual, if you have an article for submission, simply send an email. I can typically get these formatted into the blog and prepped for posting quite easily. Please ensure that your imagery is cleared for usage and cited. Creative commons licensing is welcome, but if you have specific permission, that will work as well.


    Ref the 15 km impactor traveling at 25 km/s mentioned in the article text… parameters run through the “Impact Effects Program“:

    “Energy before atmospheric entry: 1.66 x 1024 Joules = 3.96 x 108 MegaTons TNT”

    “Transient Crater Diameter: 100 km ( = 62.3 miles )
    Transient Crater Depth: 35.5 km ( = 22 miles )”

    http://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=1000&distanceUnits=1&diam=15&diameterUnits=2&pdens=&pdens_select=3000&vel=25&velocityUnits=1&theta=45&wdepth=&wdepthUnits=1&tdens=2750

  2. “The amount of uplift would indicate a possible explosive VEI 2 or possibly low VEI 3.”

    Good post, but I don’t think we can make predictions on presumed eruption size based off uplift – at least not reliably. I’m not saying we will or won’t see something larger at Sakura-Jima. The problem is that we don’t know how much magma is ready to be pushed out, how compressed that magma is, how gas-rich that magma is (which expands way more than icelandic basalts do), or many other factors that are at play here.

    As a point of reference, Pinatubo saw only a very small amount of uplift prior to firing off a VEI-6 eruption. Pre-eruption inflation is often caused by magma pushing into a conduit, trying to leave the magma chamber below. In the case of SakuraJima, it seems this magma is pushing out stale, degassed magma, which is why we see the lava dome showing here. With that said, this push isn’t indicative of possible eruptive size, since it’s simply the magma within the conduit that’s trying to push the cork out (the dome). The magma that has potential to erupt is mostly sitting inside the magma chamber, and we have no idea how much will or won’t erupt if a larger eruption gets fired off.

      • A few reasons. First, I’m only referencing the top layer of magma, or the dome itself. Think of Kelud, which had a degassed dome on the surface for quite a while before its eruption this year. Clearly, based off explosiveness, Kelud wasn’t degassed, but the dome itself on top was.

        Lava domes are very often higher silica magma that has had its gas removed. As such, they’re brittle, pretty stiff, and generally pretty tough to move. Hence why they often cap volcanoes, forming a plug for the gas-rich magma bnelow.

        As for why we’re seeing so2 and h2o, as lurking mentioned, there is still some gas in there in all likelihood, but not enough for it to cause a large eruption. Also, its quite likely that a lot of the gas is seeping out from deeper lying magma that doesn’t compose the dome.

        • Thank you. Sakurajima was very active before the current quiet period so how much old magma would still be hanging around?

          • Who knows? Pretty hard to tell without taking a shovel and digging out the magma from the conduit (obviously this isn’t going to happen).

        • …well, if you go by the 5% eruptable magma rule of thumb, there could be quite a sizable amount still lurking down there from all of the previous eruptions.

          Example, if a given blast releases 1000 m³ of DRE, that’s 20,000 m³ that did not make it out and still oozing around down there as an emplacement… slowly cooling, eventually to become a pluton. That is, unless something comes along and remobilizes it.

  3. @Henrik, thank you for the follow up article 🙂

    Struggling with a personal project but may get time to do an article after that in a week or so’s time.

  4. I may not quite agree with your proposed role of impacts. The Mexico impact happened long before the TMV formed. The reference to a Deccan Trapps impact probably refers to the ‘Shiva Crater’ which is not accepted as an impact feature. It is not round, for instance. The largest recorded impacts (Vredefort in South Africa and Sudbury in Canada) did not lead to geological break-ups, and these were much larger than Chixchlub. Impacts of that size should trigger volcanoes wide and far, but that is a temporary effect.

      • It has been documented that there are volcanic products near a few impact craters – obviously caused by impact events. I wish I had a link, but I know Erik Klemetti mentioned it from a canadian impact crater before.

    • I thought the Deccan Traps were the result of India traversing the Reunion hotspot, which then accelerated it into Asia. An impactor is interesting though.

    • http://www.newgeology.us/

      If you want to go far out into loon-land, you can go with the shock-dynamics theory, in which they feel all geology was started by some impact near to Madagascar. But… this is loon land, therefore not real.

      • I am of the opinion that “loon” ideas are akin to the beginnings of most folklore, touching on something or some phenomena that was observed at one time or another. In that line of thinking despite it being related to a moon-bat idea, that doesn’t automatically dismiss it. Whatever it is, it should be examined on it’s own merit… or lack of merit.

      • Given that we know India has impacted into Asia, forming the Himalayas, where sea shells are sometimes found, and that it’s origin is understood to be somewhere near Madagascar, an impact would seem to be the likely propulsion force.

        • Or it could just be normal plate tectonics, which have been ongoing for over 5 billion years on our planet, causing continents to converge and separate many times over Earth’s history.

          With that said, I do agree that an impact *could* have played a role however in events of this nature.

          One theory I personally have is that large trap events aren’t actually from antipodal impact events, but are instead the result of the puncture / wounds created at the site of an impact. As Henrik mentioned, a comet / asteroid that hits with enough force will puncture incredibly deep and do tons of damage to the crust. It would seem likely that this would be a good environment for the creation of a mantle plume. In some ways, you could look at it as a needle would strike a water balloon.

          I don’t think this scenario has been considered as much as it should be (even though antipodal impact theory is more well-discussed). I think the reason being is that many assume you need to find an impact crater for there to be such an event, but there aren’t many things better at hiding a large impact crater than a million-year long trap event such as the Siberian Traps or the Deccan traps. We also know that some impact events have created subsequent volcanism, so the idea is far from outside a possibility.

          • Just look at Mars and you can easily identify some gigantic stumbling blocks that the antipodeal idea will have to explain away. 🙂

          • The thing that most swayed me away from the Antipodal Impact theory is the realization that most comets / asteroids strike the earth at an oblique angle. Since the energy transfer in an impact event like this is linear, the energy shouldn’t go directly to the antipode unless it’s a direct head-on strike.

          • The energy of the impact is released as heat, when the rock suddenly comes to a halt, and vaporizes. This is the explosion and is why impact craters are almost always round (only very oblique impacts give elliptical craters). There are cases where the shock waves traveled around the planet and fractured the opposite side: Caloris basin on Mercury has done this, but it was a much bigger impact than any recorded on Earth. Most of the energy goes up into the atmosphere, rather than down. That is true for volcanic explosions as well.

    • Been watching for a while now, that cloud on the left seems to be coming from the volcano from a source behind the Showa Crater.

      Source as above.

  5. I love it when people do not agree with me if it leads to a discussion! So let us take a walk in ”Loon Land” as someone put it and see if it is that loony after all!

    First of all, the “official” figures for the Chicxulub impact: Calculated as impactor diameter 10 km, estimated energy equivalent 100,000,000 megatons of TNT (4.2×10^23 Joule).

    One of the basic principles of physics is that energy cannot be destroyed or disappear, it has to be accounted for and can only be transmuted into a different form. This leaves us with four main avenues for energy dissipation if we ignore atmospheric ablation prior to impact:

    · Kinetic rebound – much material, both from impactor and the impacted area, gets ejected and some even with enough energy to achieve escape velocity. The majority however returns to Earth and will have to dissipate the energy in another way
    · Heat – at the very point of, the front of the collision, temperatures will be raised to several tens of thousands of degrees (I might return to the implications of that later)
    · Seismic and sonic shock waves
    · Matter displacement which accounts for the majority. Some of it ends up as potential energy (the raised ring) but the greater part will have to find another way to dissipate (heat)

    Let us say that a mere thousanth of the energy dissipates as seismic shockwaves. That equates to the equivalent of 100 teratons of TNT or what would be released by a M11 earthquake. Please remember that the 2004 Indian Ocean quake, a feeble M.9.2 in comparison, caused the entire planet to vibrate as much as 10 mm, triggered other earthquakes as far away as Alaska, generated a seismic oscillation of the Earth’s surface of up to 20–30 cm (8–12 in) equivalent to the effect of the tidal forces caused by Sun and Moon, moved the entire Island of Sumatra (36 m IIRC) and affected the Earth’s rotation so that the day was shortened by a minute fraction of a second.

    The point of impact was in a shallow sea, meaning that there was only a thin oceanic crust overlain by sediments so the depth of the crust at the point of impact would have been no more than 12-15 km, thus the impactor would have punched straight through and deep into the astenosphere. This would exacerbate the seismic shock caused to that plate – just relate to how armour and kinetic anti-tank projectiles interact! The crustal plate would have been overmatched to the point where the majority of the kinetic energy released would have hit it from below, exacerbating the damage caused. Most likely, the small continental plate struck was split into several smaller fragments one of which may have played a (minor) role in the ensuing volcanism, something Lurking pointed out in a comment on the previous topic. Just to be perfectly clear – I am not saying that the Chicxulub impact in any way caused the TMVB, only that it would have had a great impact on local plate tectonics at the time wich in turn may have had an ensuing effect on volcanism during the 40-34 MY period and possibly 7 MY to present.

    🙂

    • In their bulletin INFORME DIARIO DEL ESTADO DEL VOLCÁN COTOPAXI No. 80 posted on Thursday, August 20th, the IG-EPN state that the volcano is “Activo en erupción”, that is in eruption. The IG-EPN bulletin also states that between 18h00 (Wednesday) and 06h00 (Thursday), there have been 52 seismic long-period events (LP) and 40 episodes of eruption tremors. 🙂

      http://www.igepn.edu.ec/red-de-observatorios-vulcanologicos-rovig/1140-informe-diario-del-estado-del-volcan-cotopaxi-no-80

      Your information is from August 17th, that’s last Monday, and before this part of the volcanic cycle began. Since then, there has been almost continuous explosive emissions of magma even if the amount emitted with each explosive event is minimal.

  6. I am not so sure of that conclusion based on translation. “….. A volcano “eruption in progress” is showing the output magma shaped domes, lava flows, eruptive columns, ash and / or pyroclastic flows.”

    The “and/or” could exclude domes, lava flows. I am probably just nit picking. But there have seemed to be some close hugging ash flows that could be pyroclastic flows. (: – ) Most of what I have seen, however, was from backside of active area.

    I do think that it is not far from some lava emission. however, as some of the eruptions have been quite vigorous.

    • Hmm, I’m beginning to see your problem. I’ll try and explain and sorry if it seems I may be “trying to teach grandma to suck eggs”. 🙂 First there is a general tendency in society to believe that the capabilities of satellites as portrayed in films such as “Enemy of the State” are true and absolute. Not so. To use an analogy, if you put the kettle on and then go to the living room, will a thermometer waved in the air from there tell you when that kettle boils or even that it does?

      Then magma and lava are two near-synonyms, almost the same but not quite. While still inside the mountain, molten rock is called magma and contains volcanic gases – water, sulphur dioxide and carbon dioxide. If there is enough volcanic gases contained, especially and primarily water, it will erupt explosively which shatters the molten rock into fragments that rapidly cool into small shards of broken glass – ash – which mixed with hot water vapour constitute the grey clouds we see on the Cotopaxi webcams. Heat comes in small, short pulses and quickly dissipates which is why an orbital instrument will not pick it up most of the time. Gray volcanism is another commonly used term for this type of eruption.

      If the magma does not contain enough volcanic gases, it may collect in the crater as a lava dome, roll down the flanks as lava flows or be thrown out of the crater as lava bombs. So you see that lava is another word for “already erupted magma that forms larger bodies of rock”. Although the evolved magmas with a progressively higher silica content – andesite, dacite, rhyolite – may form these flows such as at Sinabung, usually it is basaltic magma that does this and because of the discernible red colour of basaltic lava lakes, fountains and flows, it is referred to asRed volcanism.

      Trust me and definitely you should trust the IG-EPN! Cotopaxi is in eruption and erupting evolved gas-rich magma that forms these billowing, dark grey clouds of ash and water vapour mixed together.

      • The downside is “Gray volcanism” can really mess up your day. Evolved magma typically means silica rich, and quite viscous. So much so that when it does finally release it’s gas, it does so explosively… shattering the rock like glass.

        • Thanks for that. I woke up after midnight and checked site and probably did not have all my thoughts together, fwtiw. lol

          Surely Cotopaxi is in eruption mode with very vigorous gas/solid particulate emissions which seem to be getting stronger with time. I do not believe any really hot, glowing emissions have been recorded yet although I have noticed mountain-hugging rapid down hill flows that from distance seemed to have pyroclastic flow characteristics.

          The extent of the grey ash fall out is becoming quite wide-spread as seen on other time-lapse videos on http://www.igepn.edu.ec/cotopaxi/camaras-cotopaxi site. This, like GL suggests must be causing discomfort to people down wind of eruption and perhaps health concern because of high silica content.

          It does seem that Cotopaxi is heading toward a new, more vigorous phase of eruption. Best regards, Bio

    • Interesting. I watched a miniseries about that feud yesterday. Its a very interesting part of US history that is often forgotten over here.

    • I resemble that! anyway, getting my new hard drive run here.. Thanks, I was just talking to my computer guy and he Joked;”ever run into any Hatfields?”
      I said: “No, but my dad did-my mother..”
      (her grandpa.)

  7. Hello from very smoky (no real close fires)NE Oregon. had a hard drive barf on me and it was messy. got the data and a new hard drive -lots faster.
    “My powers are weakened under a red sun”..

    • I switched to a chromebox. no more windows, hard drives, crashes, virus. everything works.

    • Did a server move today. Destination site did not have their drop active and the IT guy was pulling his hair out trying to get the provider to get a crew out to turn up the circuit. Glad it wasn’t me. His office is literally not operable until that circuit comes up. (a Tag office). Frustrated, he and his group went to lunch and I finished setting up my side of things and did a system check of what I could and was happy. I had a couple of spare drives with me in case his RAID array had a drive go belly up. They weren’t needed. As a side benefit, unlike the HP servers I have had to move for them, the heatsink on the Northbridge had not fallen off. Evidently, while under the guide of a previous CEO, HP let their quality control slip a little bit and the stirrup clip for that particular Heatsink tends to pop loose from the motherboard due to a cold solder joint.

    • I hate those red smoky suns, they are beautiful, but scary, one never knows who is suffering with fires from it

      • here it is raining buckets, the greeks are running, the river is up, not going anywhere for a few days by the looks of it, waiting for a lull to feed the animals then, Marvin is telling me to hurry up, to get him inside, to get comfy under the bed, things are very slippery, water in the paddocks, got some duck a couple of weeks ago, they are happy, I suppose perfect duck weather, it has been colder then usual this winter, mostly frost and sunny, that is life

    • It’s turned a bit cloudy now but you can see this pic from a little earlier, from Twiiter

    • Just a friendly warning to users of en-vivo site, mute your speaker volume first as there is an obnoxious advert that will blast you out of the room the minute you connect. Good pic angle thou. (: – o).

  8. Booya! Who says you can’ teach a girl from Iowa how to make red beans and rice!

    Zatarain’s, the great equalizer. Add a bit of smoked sausage and it kicks arse 😀

  9. And talking about Henrik’s beast, the link shows population density around the central Mexico volcanoes. The area around the Michoacan-Guanajuato volcanic field is especially noteworthy, with 5.7 million people living within 10k of a volcano – the highest number in the world (second is Tatun in Taiwan, and third Leizhou Bandao in China). Leon has 1.7 million inhabitants. These are not necessarily the most dangerous volcanoes, but it is interesting that the population density is lower around volcanoes that have had a recent eruption. Sleeping volcanoes are more populated. In the tropics, volcanoes are attractive: the soil is fertile and the climate at altitude is better. But the heavy rain makes eruptions more dangerous as well.

    https://www.ldeo.columbia.edu/~small/Volcano/SNFig4.html

    • I read an article about that years ago… evidently, mankind tends to conglomerate around places where the mineralogy is more easily exploitable. That is usually around geologically active areas. In the past, civilizations accumulated near the outcrops that made Rio Tinto what it is. “In approximately 3,000 BC, Iberians and Tartessians began mining the site, followed by the Phoenicians, Greeks, Romans, Visigoths, and Moors.”

Comments are closed.