Southern Japan Calderas

The 5 Sisters of Kyushu

As someone who is interested in volcanology, I’ll admit that I find large eruptions and large calderas way more interesting than effusive or smaller eruptions. Regardless of size, there is a lot more intrigue with large eruptions as they’re simply more of a mystery than small eruptions.

Ikeda caldera. Photo by kazukariya (Panoramio).

The Ikeda Caldera is a “small” 4x3km caldera that sits inside the much larger 20km Ata caldera at the southern tip of Japan. It now forms an extremely scenic vista with the Kaimon-Dake somma volcano in the background. Photo by kazukariya (Panoramio).

Much of the mystery behind larger eruptions is due to the fact that we rarely see them. Pinatubo’s vei-6 eruption took place over 20 years ago, and even that doesn’t hold a candle to some of the larger eruptions that have occurred during the last 10,000 years. The only VEI-7 eruption in historical time that people were around to witness was Tambora, which thankfully took place in a relatively isolated area (which is why Krakatau’s much smaller eruption around 50 years later still gets more publicity).

Now imagine if you were to take a volcano that produces eruptions 40 times more powerful than Pinatubo’s 1991 eruption. Then place that volcano on an island that’s slightly larger than Taiwan. Then for good measure, copy that volcano four more times, and place those on that same island. Finally, lets make sure the island is extremely populated with high levels of population density living close to most of these volcanoes.

With that example, we arrive at Kyushu – southern Japan.

While the above example may sound extreme, it’s the reality of a live volcanic arc that overlies a graben with very thin crust (more on that later). Despite the fact that there are so many huge volcanoes in such a small area, there are other similar areas in the world such as New Zealand’s north island (Taupo Volcanic Zone).

The five major calderas in Kyushu from south to north

  • Kikai: Source of what is likely the largest eruption in the last 10,000 years. Despite being south of Kyushu, the eruption that occurred approximately 6300 years ago blanketed Japan in ash, and devastated the entire south and central areas of the island. According to the GVP, the southern part of Kyushu remained uninhabited for several centuries after the eruption occurred, despite it occurring relatively far offshore. It’s believed that Kikai is the source of more than one caldera forming eruption.
  • Ata: The Ata caldera lies mostly submerged at the southern tip of Kagoshima bay. It’s last major eruption was a little over 100,000 years ago, making it the least recent eruption. Despite no recent caldera forming eruptions, Ata has been active in the last 10,000 years. Mt. Kaimon forms a somma stratovolcano, and the 4×3 Ikeda caldera formed approximately 4000 years ago near the slopes of Mt. Kaimon.
  • Aira: Aira is the home of the ever-erupting SakuraJima stratovolcano, which forms a landmark in Kagoshima bay as a somma volcano on the southern end of the caldera. Aira’s eruption 22,000 years ago formed the massive Ito Pyroclastic flow, has been documented as traveling in a radius as large as 90km from it’s source. To give a sense of scale, the pyroclastic flow alone from this eruption was likely larger than the entire state of Connecticut. This does not include the massive ashfall and lahars the rest of the island would have had to deal with. Around 16,000 years ago, a smaller caldera forming eruption occurred on the northern end of Aira’s caldera. The size of the caldera was approximately 6×3. Currently, SakuraJima has had quite a few larger eruptions as Karen wrote about here , although it seems mostly content with strombolian activity at present. (source)
  • Kirishima: Kirishima sits north of the Aira Caldera, and is the site of a small stratovolcano and numerous monogenetic and basaltic vents. Just north of where Kirishima’s primary center of activity is sits two separated calderas, those being the Kakuto and Kobayashi calderas. These calderas are older and smaller than the other major caldera centers in Kyushu, but still are massive in their own right.
  • Aso: Aso is the northernmost major caldera in Kyushu, and had a series of four massive eruptions from 300,000 to 90,000 years ago. While Aso is part of Kyushu, it sits in a different geological setting than the 4 previous volcanoes, although the overall environment is roughly similar. The final eruption in this series was likely the largest eruption in Kyushu, with Pyroclastic flow deposits traveling over 160 km from the source of the eruption. Aso has several resurgent domes and volcanic cones inside the caldera limits. (source)
Known Caldera Structures denoted in Pink

Known Caldera Structures denoted in Pink

The Kagoshima Graben – Aka, a Recipe for Large-Scale Volcanism

Volcanic arcs occur around the world just about anywhere in which subduction occurs. So it’s a pretty easy question to wonder why some areas create huge calderas, while most subduction zone volcanic arcs such as the Cascade range see more standard andesitic stratovolcanoes.

Before we tackle this question, it’s important to understand how magma is created. In a fairly simplistic manner, there are three basic mechanisms which influence magma generation.

  1. Heat: If you heat rock up to a high enough temperature, it will melt just like any other material in the universe. With that said, rock does not melt naturally until way far deep inside the earth. If heat were the only factor in magma generation, we would likely have no volcanoes, since the rock would be way too deep in the earth when it melts to ever see the surface.
  2. Water: Water is the main reason you see volcanoes around subduction arcs. Water has a way of changing the melting temperature of rock. When you saturate rock in water then heat it up, it suddenly requires much less heat to melt the rock. Because ocean crust is saturated in water, it naturally forms magma pockets as it sinks beneath less dense continental crust.
  3. Pressure: Much like water, pressure changes the temperature in which rocks melt at drastically. The lower the pressure, the easier it is to melt rock. Given extremely high pressure, rock can stay in a somewhat solid state incredibly deep in the earth. Given extremely low pressure, rock will melt at a surprisingly low temperature. If you ever hear the term “decompression melting”, it’s generally referring to magma formation due to a lower volume of pressure in an area of crust. Low pressure is typically caused by crustal stretching and rifting. This stretching thins the crust greatly, which allows magma to well up from depth with ease, and gives greater access of heat towards the shallow bedrock.

So… how does this relate to Kyushu volcanism?

Most subduction arcs generate magma through mechanism 1 and 2. Just add heat and water, and voila, you have a volcanic arc. But what happens when you see decompression melting in the same zone as a volcanic arc? The answer can be found just about anywhere you would find a string of very large caldera systems: you see large rhyolitic caldera complexes pop up.

Decompression volcanism in subduction arcs is most likely the predominant formula for what drives the creation of what the media refer to as “supervolcanoes”. If you look at most known “supervolcanoes” outside Yellowstone, they sit in crustal rift basins or grabens above subduction zones. Keep in mind, there are other very large volcanoes and calderas that aren’t in rift zones, but this seems like the most common way in which massive caldera volcanoes are created.

For Kyushu specifically, the primary source of decompression is what is known as the Kagoshima Graben. A graben is a block of crust that has sunken down into the mantle between two faults. The Kagoshima graben can be easily discerned, as it forms the trough of Kagoshima bay itself (which contains Aira and Ata Calderas). The graben runs north south, and continues beyond the bay north until approximately the Kirishima Volcanic Center, and continues south into the ocean as it runs through Kikai Caldera. The crust in the Kagoshima graben is extremely thin (source), which serves to lower pressure below the graben, and allows very hot magma to well up to extremely shallow depths. This likely underplates the already thin crust with fresh hot magma, resulting in the melting of granitic bedrock, and the formation of large rhyolitic magma complexes. The actual process of magma creation in zones like the Kagoshima Graben can be more complex, but this should provide at least a basic understanding of how it works (I encourage any experts to chime in here and offer additional input or corrections).

While Aso is not part of the Kagoshima graben, it is part of another similar graben in Northern Kyushu, which is aligned with Unzen and Kuju Volcanoes. Aso also overlies

Sakurajima sits at the southern boundary of the Aira Caldera in Kagoshima Bay – Image courtesy of Wikimedia commons

Implications for future volcanism: How do these volcanoes affect Kyushu and Japan?

I believe most people have the common sense to realize that any large VEI-7 volcanic eruption would be quite a problem in terms of a disaster. Environmental impact has been well documented from eruptions such as Tambora, and it’s unknown how it would affect the world food production chain.

With that out of the way, If we’re limiting our eruption size to VEI-7, I can’t think of any worse place for an eruption to occur in terms of disaster mitigation. Most of the caldera forming eruptions in Kyushu devastated large portions, if not the entirety of the island. With a population of over 13 million living on the island, and very few ways to organize a mass evacuation (only one bridge to mainland japan), a large caldera eruption in Kyushu would be a disaster without anything close in historic scale. Outside local devastation of Kyushu, assessing global risks to the economy, environment, and other variables such as nuclear meltdowns which would be impossible to stop if they were to start could affect the world (as we now realize is a reality based off the 2011 tsunami).

Luckily, like most very large volcanoes, the large eruptions are extremely far apart, and we’re not likely to see any Aira style eruptions for quite a long time. There is also no sign of impending eruption from any of these calderas outside small-scale activity.

Currently, the greatest risk are from smaller eruptions from somma volcanoes like Sakurajima, which sits close to highly populated areas such as Kagoshima City.


120 thoughts on “Southern Japan Calderas

  1. Fantastic post CBUS, I loved reading it.

    Now finally I am about to cross the street to find that vodka bottle without being eaten.

    • (No, not vodka! I hadn’t seen Carl’s post!) Something more suitable, like Vulkanbräu or something.

  2. PS, it would be timely to point out that while these eruptions can be 40 times larger than
    Pinatubo, they do not necessarily impact the climate 40 times more severly. On the contrary, they generally issue large amounts of ash (that drops out of the atmosphere relatively quickly) and relatively little SO2 which is why they often don’t show up in the ice record. This is not a hard and fast rule, just a general trend. Whether this applies to Kyushu I have no idea.

    • .. which of course is not much comfort if you happen to live in Kyushu or the Korean peninsula for that matter… cbus, do you know how any of these eruptions progressed over time? Did they start slowly (like the last Taupo eruption) and suddenly go caldera? It might be interesting to see if there is some pattern to these mammoth eruptions. If they all start slowly there might be enough time to evacuate. (Lord, I’d hate to be the volcanologist on duty having to draw the limits of the exclusion zone, imagine it).

      • I don’t believe they started as slow eruptions. From what I know (primarily from Aira), they had stages, but it started large and only got larger. I know the Aira eruption was originally thought to have started at the northern end of the caldera, but more recent research seems to believe it initiated around the area in which SakuraJima currently sits.

        Most of the Kagoshima volcanism intensified in the last 300,000 years, resulting from slab rollback.

  3. Great post, though possibly a small chunk of text has been chopped out by accident?
    The sentence “Aso also overlies” seems to have come to a halt abruptly.

  4. I feel I forgot a few small details when sending the post over to Spica. Feel free to edit these in to the original post of desired.

    1. With the exception of the Kakuto and Kobayashi calderas that are part of the Kirishima volcanic center, all of the calderas are roughly the same size (approximately 20×20) square miles, with Ata and Kikai being slightly more oblong, and Aso and Aira being more circular.

    2. The calderas in Kyushu all have a strange commonality in that their collapse structures form funnel-shaped depressions, instead of the more common “piston” style caldera collapse. I’m not sure the reasons why they all behave in this manner, but it’s somewhat unique in that they all act in this manner. I’m curious to know if New Zealand calderas are similar in this regard (result of extreme explosivity?)

    3. Aso’s sits in a slightly less active graben than the Kagoshima graben, but it’s influenced by the subduction of an extinct volcanic ridge, which currently lines up directly under where Aso is located.

    4. While the Kyushu caldera systems are extremely unlikely to erupt in the near future, when you compare them to other huge caldera systems and eruption cycles, they actually erupt way more frequently. There have been at least 8-9 large VEI-7 eruptions in the last 300,000 years in Kyushu, which geologically speaking is quite frequent for such a small area. The only volcanic area in the world that comes close is New Zealand, which we all are aware of how prolific it is.

    • NZ calderas represent a wide assortment of morphologies. You have monogenetic calderas like Rotorua which are generally circular and I guess are kind of piston like structure though it is hard to know due to all the infill hiding their true shape. Then you have multiple event calderas like Okataina and Taupo that are blasted six ways to Sunday, though the Bouger anamolies here do reveal a curiously oblong shape, the long side of which is perpendicular to the main fault line running through the system. Whether they are round piston like structures or just some kind of chaotic explosion/collapse structure, I can’t tell you. And then you also have trap-door calderas like Reporoa which blasted its ignimbrite out towards the east.

    • Oh, and there is also speculation that there is another similar sized caldera that is either related to the Ata caldera system between the locations of where Aira, and the more well-known Ata caldera location lies. It seemed a bit too speculative to list however as some texts and maps listed and referenced it, while others only mention one caldera structure in the Ata area.

      The northernmost caldera (just north of Aso) is a buried caldera that’s most likely extinct in terms of further caldera activity. This caldera is related to the Kuju volcanic system, and is approximately 9×6 km. The outline for it isn’t really accurate, but was just shown to depict that there IS another decent sized caldera north of Aso (erupted just short of a million years ago).

      Finally, it’s worth noting that most of the flat land in which cities are built in kyushu (near shores and in basins) is built on top of settled pyroclastic material.

      The scary thing about this area to me, is that in a hypothetical worst case scenario, there really would be no hope to evacuate most of the people living close by. All you could really do is just pray that the volcano has a smaller eruption in which you can get to a far corner of the island and avoid the pyroclastic flows. Japan has some of the best monitoring and mitigation of any country in the world for volcanic threats, but the logistics of evacuating 13 million people off an island via a single bridge just is not realistic. Airplane and boat aren’t particularly efficient answers either.

      • see my comment about Taupo above. This thesis is worth a read (though it is 200 odd pages) but it makes it clear how long and how “small” the last Taupo eruption was before the Y7 ignimbrite sheet was erupted. The main issue is when and how do you make the call between deciding the eruption is going to stay like this (moderate ash fall) or go cataclysmic?

          • yeah, I don’t mean you should read the whole thing! (there is a lot of discussion about proximal, medial and distal ash fall and it is kind of interesting to see how they interprete the results). Also interesting to see how water plays a role in the actual form of the tephra that gets erupted.

  5. Oh, and finally – another anecdote on the fact that there are more caldera structures here that simply aren’t that well-known or understood:

    “Submarine calderas, Kuchinoshima,Takarashima and Amami calderas, which are of the same size as the Aira caldera,on the Tokara volcanic ridge that is the southern extension of the Kyushu Island, have been proposed on the basis of the bathymetric data.”

    I got that from the following link:

    • .. which would put us in the same ball-park as the TVZ in terms of frequency over the last 300,000 years, assuming that anything older would be buried by now.

      • Pretty much. I think a somewhat realistic number is an average of a VEI-7 every 25-30,000 years in south Japan.

        • which, coupled with a frequency of roughly one very 15,000 years in the TVZ already amounts to a frequency of one large ignimbrite eruption every 10,000 years just from these regions alone. Now factor in the Americas, Kamchatka, the Philippines, Indonesia, Micronesia.. and the Mediterranean.. hmmm. food for thought. Where is that vodka? Carl?


  6. … meanwhile, sitting in a parking lot in the rain, I’m waiting for someone to return a phone-call. Two laptops, 60 miles apart, neither point of contact will answer the phone…

        • @Bruce Stout. The part about this that ya missed was when I went to get a burger. I arrived just in time to see a 55 person bus unload at the restaurant. Evidently a tour group from Tennessee was going to Panama City… I went through the drive through and went and parked in the overflow lot next to the trees and bushes. Ate my burger and watched the rain, waiting on the phonecall that never came. Hell, even my dispatchers couldn’t raise anyone. I told them “If you guys can’t give me some direction as to what you want me to do, I’m headed to the house.”

          I did have a clean schedule with only those two calls to worry about, now I have had three others come in that take higher priority due to contracts. The laptop calls are gonna have to take back burner.

      • The part that pisses me off, is that I started on this endeavor on Friday, got 45 miles into the trip, and was advised by the IT guy that he was headed out of town. So, I called the closer site and they noted that the site’s point of contact and his assistant were gone and that their stuff was locked up tight. The IT guy, the main coordinator for all this indicated that a Monday repair would be an easier solution, and not one single person can be found. Voicemail only. Even called the main number and the duty person never answered… but I did get his voicemail, and a friendly reminder that if it was an emergency to call 911.

        I be fuming.

        Originally, I was apprehensive about the two calls due to what I had to do to them. One is a motherboard replacement, the other is a keyboard. I’ve done several motherboards and they are nervewracking. You are always at the mercy of whatever dim wit ideas some engineer had when he laid out the chassis design. As for the keyboard… it’s on a ruggidized chassis, so it has extra-special engineering added to it’s over all design. (22 screws to remove a bottom cover? WTF?)

        On a bright note, I get home and the wife is terrorizing the dogs. She has the vacuum cleaner out and the dogs don’t know what to do. (no, she is not trying to vacuum them, but they could probably use it)

        • at the moment I am putting off PC work until I moved my office and have an empty table, plus peace, it needs some things done, I get the shits when I get told to get a new whatever instead of fixing things, more fun in a way, my keyboard works mostly fine after taking it apart the last time, I got some others for replacement parts, this will be no uno

  7. …Mount Merapi on the main island of Java rumbled as heavy rain fell around its cloud-covered crater, said Sutopo Purwo Nugroho, disaster mitigation agency spokesman. The volcano unleashed a column of dark red volcanic material 1,000 meters (3,280 feet) into the air, and the ash made the rain thick and muddy in several villages as terrified residents fled to safety, he said. The sound was heard 30 kilometers (18 miles) away, but an eruption did not occur and the volcano’s alert level was not raised, Nugroho said….

  8. Another interesting post ! An interesting link that explains the different stages of the Japanese volcanism :

    Click to access TR-09-02-5.pdf

    As for Tolbachik, the eruption seems declined and the authorities could decide to close the only road to the site of the eruption. This decision is motivated by the imprudence of tourists during their visit.

    //Hope you enjoyed the cookies 😉 chryphia

      • Hi Frances! Long time no see (or rather read). Been texting my sister-in-law with the royal baby news – their TV was knocked out by a storm (I think) just before the news broke. No rain here yet, still lovely and hot.

        • Hi Talla, I am desperately waiting for some rain, I have spent my last two weeks watering my very large garden and also my friends garden and allotment as well as being very busy with hospital appointments,fortunately not mine but a family member who is now much improved. This hot weather though along with the constant watering has given me the best show of flowers in my garden that I have ever had in the 17 years in this house. Hard work but worth the effort. Now I want it to stay warm but rain every night. LOL 😀
          No chance I can catch up on all that I have missed so I will take it from here.

            • No rain in this part of west Wiltshire, but I hear it’s been in the Salisbury area. Lots forecast for tomorrow. It’s a shame we can’t arrange for cool rainy nights and warm sunny days! I love storms at night. My garden is a mess, but a tree surgeon is coming on Wednesday to take out a huge eucalyptus stump, then I’m getting the retaining wall rebuilt and then I can start doing things!

  9. Hi all,

    Back to my gardening off topic question. Thanks for your replies, the especially useful ones were the suggestion of kimberlite as the rock rich in potassium, to go to the edge of of glacial plains to look for silt as a nice source of many minerals, and the use of deep groundwater as a source of other rare minerals (and in Iceland, this deep groundwater sometimes reaches the surface, in hot springs)

    Of course I know that nitrates, urine, manure, humus, mulch and decaying organic matter, are all rich in nitrogen (and other elements), and limestone is rich in calcium. That’s the conventional knowledge. As other trivia like greensand as a source of potassium. I know very well all of this. What I am trying to think here is outside of the box. Since I live in a volcanic land, with amazingly diversified volcanism, I must be able to source the minerals from the ultimate original source, not from manure, humus, limestone or sedimentary rocks, but from the magma itself (but of course cooled down as lava rocks, ash, pumice) As I obviously can’t imagine myself pouring hot magma over my plants 😉

    I tested the other day the soil here, and the volcanic sand in this region (black) is very rich in phosphorus, while the native clay is rich in potassium. These minerals must come from a volcanic source. Well, the clay is washed from Langjokull, and the ash comes from Katla, Grimsvotn, the ones that erupt dark ash.

    What I want to ask is whether some of you know, of other rocks (or minerals) where the atoms of nitrogen, calcium, potassium and phosphorus could be, it does not matter the form, because of course I know it is inorganic form, and therefore mostly unavailable for plants (unless it leaches gradually into the water or chemically reacts to form soluble compounds)

    I also want to ask if anyone has any idea of where phosphorus, potassium, calcium, etc, might be in different proportions as it erupts in different volcanic regions across Iceland. Something similar to the chemical signatures between Vatnajokull volcanoes, south Iceland volcanoes, and the Reykjanes volcanoes, all chemically different magmas.

    Because someone has one day found that greensand could be use to supply potassium, and limestone for calcium, why couldn’t I discover other Icelandic rock sources of other minerals?

    Anyone up the challenge?

    • already found that phyllite, slate, biotite schist, breccia and greenstone contain nitrogen that can be weathered with time.
      Nitromagnesite is also a mineral that contains nitrogen.
      Granite dust is also used as a source of potassium
      Fluorapatite contains phosphorus, and occurs widely in volcanic rocks.
      I am looking for more, but now I need to check which sources could there be in Icelandic volcanoes

      What about basalt? Do you know about the chemical composition of the Icelandic basalt? And per volcano, any difference?

    • Dunno. But I can tell you that one critical elemental ingredient that is gonna kick your arse is carbon. It’s a needed soil ingredient and I do not know of a volcanic source that is present in Iceland.

      • wouldn’t you get that from burnt wood/charcoal ? I live in a volcanic field, the soil here is shit, the trees I put in kept on dying, so got things in large pots, there are pines in some places and others they die once they get bigger, but then native eucalypts are fine, don’t like them to close to the house, because of fires, around the house Elm trees are doing great since I discovered a sewer leak and the water over flow from the tanks does the rest, with the garden I have been putting carpet (2nds)pieces which I had for the dog runs first, when smelly go to garden and soil I have been improving for years on top, have to get the leaves raked soon, and collect some more wombat shit, good stuff, the only other shit I like is from horses, other then that I am fine this year, digging it over of coarse, next month will do seeds and put them in green house until frosts are over, forgot Dolomite good stuff as well.

  10. Thank you cbus, what a fascinating post stimulating further reading!
    Found a good review by Hiroshi Machida “Volcanoes and Tephras in the Japan Area” (sorry, somehow google doesn´t let me copy the direct link). Figure 2 shows the gigantic distribution of the marker tephras.

  11. Leave it to Australia to stroll in and rudely bugger Saudi Arabia.

    Arckaringa basin

    It’s the biggest find in 50 years and the media is completely ignoring it…

    It is 6 times larger than the Bakken, 17 times the size of the Marcellus formation, and 80 times larger than the Eagle Ford shale.

    All told what was recently discovered outside a sleepy Australian town contains more black gold more than in all of Iran, Iraq, Canada, or Venezuela.

    With current estimates at 233 billion barrels its just 30 billion shy of the estimated reserves in all of Saudi Arabia.

    • yah, read about it the other day, thinking it is there to actually getting it out, will take time, why is everybody so keen in digging things out of the ground, leaving a mess behind, changing the earth and stuffing it up, for what, money, the one who have plenty of it seem to need more, to hide in dark places underground mostly, unreal

      • The majority of shareholders won´t want to live there I guess.
        Zero income tax for all Australians would be fair.

        When this 5.6 earthquake near Coober Pedy hit in March I immediately remembered this strange little town from the Wim Wenders movie “Until the end of the world”. It was also featured for the opal in the BBC Rise of the continents – Australia series. And now this. Hope the best for the people there.

        • Do not forget that the city was also in Priscilla – Queen of the Dessert.
          Sometimes I suspect that Cooper Peady is the center of the world…

  12. Re Katla… has any one plotted the quake set recently? The cryptodome as well as the central caldera has had some quake activity recently…

    I’m getting ready to shut down my computer due to atmospheric electrical discharges.

    • Gee, Lurk, we are running at 9% humidity and 32-34deg C.
      pushing 40 sometimes . Waiting on a fire crew boss tomorrow.
      In John Day, OR. Interesting volcanics abound there. Strawberry mtn towers. over the airport makes for interesting
      Conditions wind wise. I’ll post some bits about the Strawberries
      Later. Katla is looking interesting,btw..

      • Well, right now I’m pissed at Forestry.

        No specific reason other than what I mentioned earlier. Tomorrow I’ll be tied up on a DMV thing and I know for a fact that they are gonna be lookin’ fer me and making noise… yet when I was on site today (as we agreed to last week)… nary a soul to be found.

        Every morning when I get up to let the rat-dogs out, I put an eyeball on the outdoor thermometer/barometer gizmo (I know what the baro readings mean, my wife just looks at me like I’m an alien) anyway, the rel humidity has been EITHER 98%, or 99%, all week long.

        Right about 9 am, the temp starts to ramp up and it drops back to the 70 to 80% range. That’s the sort of weather that makes me do stuff that pisses my wife off… like keep the A/C in the truck cranked to the max. It’s not that I like the cold… I just like being dry!

        True and somewhat disgusting story.

        30+ years ago, while assigned to a base here awaiting training, I was in “T” division. Our job was to be “gainfully” employed doing landscaping tasks on the base until our school “classed up.” My first experiance with this unique Florida sweatbox was mowing the grass on the areas around the no longer used runways. My first day I returned to the barracks exsausted and fully soaked from the sweat. Took a shower and went to bed. Grabbed what appeared to me to be a clean dry teeshirt.

        That was a mistake. It was the previous day’s tee shirt. As my pores began to open, that salt quickly mixed with the forming perspiration and my skin felt like it was on fire.

        From then on, I made damn sure I knew exactly where I put the used tee shirt when I got back to my room.

        Students awaiting “class up” don’t do the mowing anymore. A few years ago they gave that job to Federal Prisoners from a nearby facility. (white collar minimum security guys). They also gave them pretty high end mowers. We had the older Brigs and Stratton powered mower decks units with the trundle behind seat on two wheels.

  13. What causes the formation of rift basins with grabens above subduction zones? Is crustal stretching and thinning above subduction zones caused by abundant magma generation due to the subduction process itself? In Europe we have several VEI7-volcanoes. The Phlegrian Fields in Italy, the ancient Lake District and Glencoe supervolcano in the United Kingdom.

    • You also have a crapload of layered old subducted plates underneath there. The Alps formed from a convergent margin. Mountian building usually happens when it’s continental vs continental crust colliding. continental vs oceanic crust → subduction zone.

      In fact, have you ever seen the Matterhorn? The top of it is African crust material. The bottom part is Eurasian crust. The terrain was folded over and eroded away, leaving the edifice you see today.

      Italy has the ancient ocean floor of the Tethys sea dangling here and there under old subduction zones.

      Over near Tivat in Montenegro, is a region of “Suprasubduction” that has since been crunched up into the mountains there and into Albania. Suprasubduction is where several phases of subduction occured. First one way, then the other, rinse, repeat.

      • @GeoLurking:
        “GeoLurking July 23, 2013 at 06:54

        You also have a crapload of layered old subducted plates underneath there. The Alps formed from a convergent margin. Mountian building usually happens when it’s continental vs continental crust colliding. continental vs oceanic crust → subduction zone.”

        The volcanic provinces in Central Europe are caused by magma generation indirectly caused by the formation of the Alps and the Pyrenees. These mountain ranges caused lithospheric buckling in the foreland region, generating magma beneath. The former subduction zone of the Alps is just north of this mountain range. More info about this subject, see Could volcanism also happen in India in front of the Himalayas mountain range? Because the Himalayas has developed in a similar way as the Alps did.

        • Just a guess, but probably so.

          The Ganges and Indus rivers flow through a downwarped section of crust in front of the main fault front of the boundary. That’s an example of the intensity of the forces at work. Will similar collision structures generate the same effects? All I can say is that it is likely, though I am not an expert.

  14. are doing a free online 10 week course “Volcanic Eruptions: a material science.” which starts today. I’m doing it, I’ve done a few other Coursera courses this year and most have been very good.
    It’s run by Donald Bruce Dingwell and this is the syllabus:

    Week 1: The Earth as a living planet: The five big extinctions during Phanerozoic times; Volcanic fatalities; Volcanism in the solar system; Volcanism on Earth; The essence of volcanism;
    Week 2: The Earth as a living planet; Volcanoes on Earth: magnitudes and landforms; Explosive and effusive volcanism; Videos of Merapi and Etna volcanoes; Volcanic materials; mineralogy and fragment classification; Chemical and mineralogical classification;
    Week 3: Structure of molten silicates: Chemical composition; Stability and geological properties (an overview on viscosity/viscoelasticity; density, expansivity/compressibility; Volatiles solubilities, diffusivities, heat capacity, redox equilibria); Structure of molten silicates;
    Week 4: Dynamics of molten silicates; Glass and molten silicates; Molar heat, Enthalpy: Strain vs. time; Cooling vs. heating paths; Maxwell relations for viscoelasticity; Resistivity and viscosity; Relaxation times and implications for experiments;
    Week 5: Relaxation in silicate melts; Longitudinal vs. shear viscosity; Glass transition; Quench rate, relaxation time and viscosity; The role of water content, water speciation, pressure and temperature; Details of water speciation from experimental data;
    Week 6: Diffusion in silicate melts; water content and water speciation (cont.); Diffusion in contrasting silicate melts; The role of temperature; Comparing diffusion of different elements; The role of pressure; Simplified Stokes-Einstein and Eyring equations; Relaxation times (comparison between different compositions at different temperatures);
    Week 7: Expansivity and compressibility in silicate melts; Partial molar volumes; Density: equation of state for liquid silicates; Density determinations and calculations above and below glass transition; Density models for anhydrous granitic system;
    Week 8: Viscosity of silicate melts; Calibration of reaction kinetics for speciation (e.g. H2O); Prediction of glass transition: temperature, thermodynamic and kinetic; Methiods of viscosity measurements; Arrheynius and non-Arrheynius plots; Viscosity-temperature relationships; Peraluminous and metaluminous (calcalkaline) melts; Adam Gibbs model: entropy of mixing; Multicomponet models with water and fluor;
    Week 9: Fragmentation of magmas. The process chain: What is a volcano doing?
    Week 10: Impact and relevance, Volcanoes and Mankind; Hazards mitigation;

  15. A quick comment. Cbus thanks for a really good post. Learned lots that made the jigsaw bits of info about Japanese volcanism that I had fall, into place.
    Went out at 6.30am to water the potted plants on the patio with buckets of saved water. This caused some atmospheric reaction and what is being described by the British Met Office as ” an energetic shower” unleashed it’s fury on me and my pink fluffy dressing gown, complete with vivid, ripping lightning and house trembling rumbles of thunder. This is Meg’s first Thunder storm. Unfortunately she was in mid “relief of Nature” when the first bolt of lightning hit. I am not sure what she thought but have a pretty good idea from the terror in her eyes and the positioning of her ears and tail as she hurtled back into the kitchen.
    Canine fear factor caused by Thunder God Thor and his anvil is equal to the Total repetitive actions of Mrs Lurking and her Vacuum cleaner. This could be an interesting behavioural study 😀

  16. Very interesting read cbus, thanks for that – kinda glad I didn’t read it before I spent a couple of days on Sakurajima 😉

    • One other thing-I was enroute between Boise Id. and John Day, Or and encountered a nice
      cinder cone on TOP of a peak, Unusual in itself. This is in the Yellowstone Hot Spot country
      with Basalt Rimrock all over the area. Thing is this appears to be quite recent- little erosion
      and sliding-geologically speaking of course.. I cannot find one single reference to it . My passenger an Air Attack pilot (Fire fighting Air Attack) familiar with the area. said he has no idea..
      More research…
      Had to be well after the hotspot galloped down the Snake River plain…

  17. After a rather eventful day of saying “Hm!” at rocks…

    Here is a good tip, never bring a muslim geologist to a place where the sun is up 24 hours a day during ramadan. It was rather freightening seeing this elderly gentleman start to shake before he keeled over unconcious. After 10 bags of intravenous fluid he came about, and we had him medivaced to London.

    Now I am off to stuff myself with the freshest fish on the planet. Hopefully without any polar bears or russians barging in.

    • Sounds like a screwed up circadian cycle and lack of nutrition. Nothing a cold beer, a ham sandwich and a good nap can’t fix.

      Note: I fully realize that my comment is culturally insensitive. Your disdain at my comment exhibits your insensitivity towards my culture. Funny how that works eh?

      Personally, I have low tolerance for the “easily offended”.

      • Well, I can pretty much bet that both the cold beer and the ham sandwich is out of the question for a Saudi Arabian during Ramadan.
        But the sun goes down in London so he will probably be able to eat there. I am amazed that he got 48 hours without food or water before he droped down.

      • True… but as a denizen of the Deep South (one of my ancestors was noted for accumulating stray hogs) and an aficionado of ham sandwiches (preferably with tomatoes and lettuce)… I can attest to their wholesome goodness.

        Bonus round, here’s a bear sign.

        • Well, I would love one of them 🙂

          The replacement geologist comes flying in from Florida tomorrow. Now I will just have to break the bad news to him or her. Namely that all the blond furry things are not Norwegian women or men… So, I will pass on the bear sign to him or her (One of them American names that could be either of) and head back home.

        • I encountered a Florida “Looker” at the State Fire College several years ago. She was from Islamadora. Talk about a cutie. Sometimes they sneak up on you and utterly destroy your concentration.

          Lucky for any victims that she may encounter on a crash scene… bunker gear doesn’t highlight features. BTW, anyone that thinks a female firefighter isn’t tough enough for the job, guess again. I’ve run across some that can put a knock down on a fire quicker than many men. On a “co-worker” scale, sweaty smoke and ash covered women smell better than sweaty smoke and ash covered men.

          And if she is brandishing a Halligan tool, don’t piss her off.

          • I have made a point of always judging people by their skills at work. I would hire a monkey with bad breath and a third leg if it was good enough to do the job.

            Women always smell better then men, with the sole exception if you are sharing the bed with a hardcore vegetarian female who had beansprouts and red wine for dinner… On the other hand… I have never, and will never, compare that to a hardcore vegetarian guy… I guess our Ladies have insights into that that are beyond my knowledge.

            • I would hire a monkey with bad breath and a third leg if it was good enough to do the job.

              I think I may have worked for that guy… The one I’m thinking of went nuts, killed his wife, and tried to burn his house down.

              My closest approach to him after his “ordeal” was to retrieve his military ID card from the local jail after they transfered him to State Prison. Other than that, he was a genuine piece of shit.

          • I evaluate all firefighters using the same standard: how capable and committed would they be if they had to drag MY ass out of a burning building?

    • ha, briilliant story. Reminds of some of those odd cultural quirks Jared Diamond talked of in Collapse, where a cultural artifact (that may once have had some kind of obscure purpose) is totally ill-suited to new geographical circumstances. Also reminds me of times where I was totally out of my depth in India and I had to sit down and seriously think about why I thought the way I did. I love it when life throws a curve ball at you.

  18. *knock knock*
    -Who’s there?
    -Magma Lavasson!

    23.07.2013 10:27:15 63.636 -19.079 16.3 km 0.7 99.0 6.3 km N of Hábunga

      • Might be a good idea if you appended the plot to the post for tomorrow that I am writing now and will edit in tonight. It would get better attention if you edit in the plot in the post, if you want to that is 🙂
        I am going to set the post to auto appear tomorrow at 6 o’clock in the evening (blog time).

        • Sounds like a good plan :-).
          The video shows seismicity of the last two months in respect to activity since 1995. To enhance visibility, the size of the recent earthquake markers are about a magnitude larger than those for the old earthquakes. And your Magma Lavasson got a ring system. You might be able to spot Earth behind it if you look closely.

          It took a while to finish the video, not because of lightning, but lighting 🙂 One fine day I´ll have to dig my teeth deeper into OpenGL to understand it.

          • I put the plot in the post.
            The post will appear on it’s own tomorrow 6 o’clock in the evening (Blog Time). If it does not appear I trust that one of the Dragons will set it loose. I will be on an airplane by then going home…

  19. Raining…. again. Dog is going spastic… as normal. Wife doesn’t feel like getting overly involved in cooking. She sugested Red Beans and Rice…. said she would do the rice if I agreed to do the red beans.

    My response? → Deal. Your on.

    Now, everybody has their own way of doing red beans. Mine is red kidney beans, (I used the canned variety since I don’t have all day to let the dried ones soak) about a pound of sliced smoked sausage, half a Vidalia onion, a bit of old bay seasoning. Boil and then simmer forever. Careful with the salt, very easy to go overboard, and you can’t go back. A bit of disolved corn starch and presto, some of the best (in my book) red beans around. Simple, tastey, and if you want to heat it up a bit, sprinkle cayenne in your bowl.

    The beauty of my version is that non pepper lovers can enjoy it also since you season it to taste afterwards. The rich Smokey flavor from the sausage provides a nice background. And if you really want to light it up, use powdered Habenero instead of the Cayenne.

    My habenero is made by decicating halved store bought habeneros, then powdering them with an espresso grinder set aside for that specific purpose. (trust me, the coffee lovers in your house would not appreciate you using the one meant for coffee beans. To do otherwise could result in blunt force trauma after they have coffee tainted with habenero)

    Note: Vidalia is a variety of sweet onion that comes specifically from Georgia. “Vidalia” is one of those “defined by law” names for Sweet Onions grown in Vidalia Georgia. But any sweet onion should work just fine.

    A sweet onion is a variety of onion that is not pungent. Their mildness is attributable to their low sulfur content and high water content when compared to other onion varieties.

    Now… that is something that I had not realized. Vidalia Georgia has to have a really low sulfur content in the soil in order for it to have such a variety of onion. That means no SO2 or H2S percolating through the soil. And no history of it for a very long time.

    Interesting. That would infer a non volcanic non swampland past. Yet it is in the region that is known to have been part of the CAMP. (Central Atlantic Magmatic Province, active when Pangea rifted and the Atlantic ocean formed)

    • Interesting , here we have Walla Walla sweets. Grown in sandy loam of the Palouse country around the Walla Walla
      River valley lots of volcanic soils here. Hmm. May have to do a bit of looking on this…

      • If I am not totally wrong (happens more that I like) most your farmable soils are Palouse loes or ground up glacier scrapings relocated by wind and some damn interesting floods

    • Seems tasty.
      I do the same for peppers, use a dedicated coffee grinder, (in my case Espelette, a pepper from the Basque country, not hot (4 on scoville I think), you can use it to replace salt).

  20. I have been watching nautiluslive exploring 3 shipwrecks in the gulf of mexico whenever i could lately. They announced they are checking out Kick em Jenny later this year!

  21. Pingback: Miscellaneous links | Zoopraxiscope

  22. Pingback: Sakurajima Update | VOLCANO HOTSPOT

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