Silicic Large Igneous Provinces (SLIPS) – there’s silver and gold in them there hills!

My interest in silicic volcanic rocks stems from childhood encounters with granite and other plutonic rocks on family holidays in the UK and continental Europe. Many of the rocks were on the sites of old mines for tin, silver, lead, iron and other ores.  I thought that this would be an easy post to put together as there was only a brief mention of SLIPs in my volcano books.  Then I stumbled on the interesting work of Bryan et al [2] ……

SLIPs are volcanic-plutonic provinces with large extrusive volumes of lava, some with volumes that exceed those of continental flood basalt provinces.  SLIPs are of economic importance in that they are associated with silver and gold deposits and their ash is mineral rich.  But, unlike their continental plateau basalt relatives and mid ocean ridges, SLIPs have not received much attention, possibly because their output, largely tephra/ignimbrites, is more vulnerable to erosion.

Fig 1: Approximate location of some large igneous provinces. Map from USGS.  Large igneous provinces added by the author. Black text = mafic large igneous provinces. Red text = silicic large igneous provinces.

Fig 1: Approximate location of some large igneous provinces. Map from USGS. Large igneous provinces added by the author. Black text = mafic large igneous provinces. Red text = silicic large igneous provinces.

SLIPs have compositions comprising more than 75% dacite–rhyolite; and, rhyodacite-rhyolitic compositions near the hydrous granite minimum (Bryan et al, 2002 [2]).  They are associated with continental break up and active convergent margins undergoing extension (back arc or arc rifting).   Both types have similar eruptive volumes: ≥ 105 km3, dominant ignimbrite, and intermediate silicic calc alkaline I-type magmas.  Large volume ignimbrites are emplaced from relatively short lived, high rate, explosive eruptions.  Magmatism occurs over many millions of years (± 40 m.y.).  This requires melting of hot mantle and sustained mantle upwelling rather than the more transient plume heads associated with continental flood basalt provinces.

The Whitsunday volcanic province, Chon Aike province and South America – Antarctica Peninsula are associated with continental break up (intra-plate magmatism) and the Sierra Madre Occidental is associated with back arc processes.

The Whitsunday province located on the North East Australian coast is a multiple vent, caldera-dominated volcanic region.  It has an extrusive volume of more than 105 km3.  Lavas range from basalt to high silica rhyolite with high calc-alkali to high potassium affinities.  Lavas originated from magma mixing of partial melt of the calc-alkaline crust and intra-plate theoliitic basalt.  Rhyolites were generated from fractional crystallisation.

The Chon Aike province in Patagonia extends from the Atlantic coast to the Andes. It has multiple caldera centres.  In the east the province is a plateau overlying crystalline basement but in the west it is deformed and tilted.  Rocks comprise phenocryst poor ignimbrites, welded and non welded ignimbrites, minor rhyolite lavas, fallout deposits, debris flow deposits and epiclastic deposits interbedded with ignimbrites.  The lavas are chemically bimodal but dominated by rhyolite.  Activity occurred in phases from intra-plate to continental margin, generated by partial melting of hydrous lower mafic andesitic crust, linked to subduction and superimposed fractional crystallisation.

The Sierra Madre Occidental province in northern Mexico compises has more than 350 calderas in a volcano-pluton belt.  Its eruptive volume is more than 250,000 km3.   This plateau is formed from volcanic rock overlying a basement of metamorphic rock.   It formed during the greatest divergence of the Pacific and North American plates, resulting in extension of the continental margin.  Its rocks are rhyolitic ignimbrites with rare mafic intermediate rocks.  Volcanics have medium to high potassium calc- alkaline.  Rhyolites may have originated from lower crust melting due to emplaced basalts or fractional crystallisation of basalt – andesites.

Fig 2: Sierra Madre Occidental.  Image by Christian Frausto Bernal, http://en.wikipedia.org/wiki/File:Sierra_Madre_Occidental.jpg (published under WikiCommons)

Fig 2: Sierra Madre Occidental. Image by Christian Frausto Bernal, http://en.wikipedia.org/wiki/File:Sierra_Madre_Occidental.jpg (published under WikiCommons)

KarenZ … not an expert.

2 July 2013

References:

1. “Eruptions that Shook the World”, Clive Oppenheimer, Cambridge University Press, 2011.

2. “Silicic volcanism: An undervalued component of large igneous provinces and volcanic rifted margins”, S.E. Bryan, T.R. Riley, D.A. Jerram, C.J. Stephens, P.T. Leat, Geological Society of  America, Special Paper 362, 99-120, 2002

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172 thoughts on “Silicic Large Igneous Provinces (SLIPS) – there’s silver and gold in them there hills!

  1. Nice one Karen … thank you

    There’s one NtV clue left to solve …
    No 6 Birthplace of a solitary dragon slayer.
    Hint … for much of his life he was famous for being very lonely … SOLVED Pinta Island … birthplace of Lonesome George the last Pinta Island tortoise.

    And very well done to the Lions … now for the Ashes!

  2. OT: does GVP note an increase in odd volcano name searches on Friday evenings (UK time) and Saturdays?

    • Laughing … if not it should do … oh, and also on Wednesday mornings whilst I struggle to set the clues!

    • Yes it is! DING! 2 points Kelda for No 6 Pinta Island home to Lonesome George a male Pinta Island tortoise (Chelonoidis nigra abingdonii) and the last known individual of the subspecies. In his last years, he was known as the rarest creature in the world.

  3. Hi in NE Oregon we have three Igneous plutons- The Wallowas which are part of the Rocky Mountains geologically. The Elkhorns, and the Strawberries. Father south- The Steen montains. My Granpa Anderson was a part-time gold miner-had a small hard rock/placer operation. Supplemented his social security some-this was when the price of gold was regulated in the USA.
    Granpa would’ve been happy with a mule, a gold pan and pickaxe and wander the high lonesome…

  4. Hi Thanks Karen!
    Can someone take a look at the White Island Crater Rim cam.. there is a glow to be seen there. In case it should be gone… i took a screenshot. Nothing spectacular but definitely something.

  5. Good post Karen Thank you. More info to digest. I really would like to believe in reincarnation as I would like to come back and study more and more . There is so much to learn.

  6. Someone knew a bit about train ops here. This is a bit fishy to me…Cars on modern trains just
    don’t “decouple” . There has to be an action to make this happen…
    My 2¢…

    • We also wonder how could a train end up on the run like that, and who had the bright idea of putting together 73 wagons of crude oil together.

      Laws will change in Canada and Quebec about transport of hazardous material, but it will not be of much help for this quiet rural city renowned for its stars observatory.

  7. not to mention tho brakes are like HD truck brakes loose the air pressure the brakes go to full lock unless manual override


  8. Hmmmmmmm! Those passengers took time to take some large suitcases off the plane with them. They must have been in the overhead luggage lockers! Would you really take time in that situation to load yourself down? Should such heavy cases be in the lockers anyway? Wouldn’t that have added to the plane’s weight?. Sorry if I sound uncaring but I never cease to be amazed at the activities of the general public of any nationality.

    • When I did my fire warden course (about 10 years ago) we were told that the first instinct of people when faced with danger, that is not clear and present, is to find their belongings first and then escape. So facing a naked flame/surging water/flowing lava (delete as appropriate) the instinct is to run fast without any baggage (though women will always grab children). When there is no obvious danger but an ongoing traumatic situation, such as a fire alarm, a car (or plane/train) accident, a flood warning etc. etc. then the instinct is to find personal belongings first and then get away. We were told that if a fire alarm went off and it was possible for people to take their bags etc. with them then that was OK as it often causes more problems when people try to run back inside to find their ‘essential’ stuff. It seems that if our lives are in a danger we can see then we run without any incumbrance, but if the danger is still not upon us our instinct is to take something that will help us survive. I guess this used to mean food but now means car keys, passports, loved ones’ photos, or overnight bags from long haul flights. I’ve been on a lot of 12 hour flights and, believe me, some very heavy stuff indeed gets stowed in the overhead lockers and under the seats.

      • Ehm, men grab kids to… It is an instinctive reflex imprinted in the human DNA to grab them, even if they are not ours. Survival of the species have played a few tricks on us.

  9. Hm, have anyone seen Ursh in a while?
    I hope she is okay…

    And here is something I would grab in a fire or airplane crash. I would probably grab it and run away with it anyhow. I am not often into thinking pets are cute, but…

    Image and video hosting by TinyPic

        • Ha! With you all the way!
          The highlight of my one and only trip to Oz was being introduced to a baby wombat that had broken its leg. My colleague and I had a couple of hours spare and went to a small wildlife centre – the boss got talking to us and then showed us round the place. Everywhere we went this little creature chased after us, stumping along on its plastered leg. It tried to get in our car when we had to leave – quite the cutest, funniest creature I have ever met!!
          (must try and find photos now!!)

  10. WooHoo … well done Andy … and Novak you’re a true sportsman …

    Andy dedicated his win to the 16 children and Teacher who died in the gymnasium of his primary school in Dunblane … some of you may not know but he was in the row of kids outside the gym in the school corridor waiting to take their turn at PE when the tragedy occured ….

  11. Talking of things Scottish! Well done Andy! Here in The UK the English language is as diverse as the multitudes of dialects. This causes problems with no only with our overseas visitors but also with Devonshire folk trying to understand geordies or Scousers ( Newcastle folk and Liverpool folk). I call a PC friend on Skype now and again. He hails from New jersey. Every time I call, his wife listens in, not because she is worried about him “Straying” but because she just loves hearing me speak the Queen’s English. We often end up in giggling sessions as we compare notes. For goodness sakes it’s H erbs.. with an H not Erbs. for example… 😀
    Then I saw this and found it so funny.
    Voice recognition in a Lift .OOOPS! Sorry elevator :D…. I hope nobody is offended .
    PS Things volcanic are really subdued at the moment…. hence I am trawling You Tube….

    • 😀

      Spanish, Greek, and Italian chip shops are to be found all over the city, all offering that unique taste of the Mediterranean. That’s right, salt.

      … Most people speak the Queen’s English, if that is the Queen had a serious case of Tourettes…

      Danny Bhoy – Visitor’s Guide to Scotland

        • Lol @ both…… Rick are you Irish? I think Lurking is American not Scottish… but Hey! You never really know what’s who and who’s what on line 🙂 Me? Definitely English with a touch of French. Sadly equal quantities of Lancastrian and Yorkist blood, tempered with a little Somerset “Swede Basher”…….. No! No ! rest easy Carl… Swede here is a large orangey, turnipy vegetable that was used more for cattle feed and only eaten by peasants. Dwellers on the flat marshy land of the Somerset levels were viewed in a similar light to American Hill Billys. My Great Great Uncle Eli and his eleven children lived in a mud Hut on Sedgemoor. My father remembered him well. It took me years to realise the Mud hut was actually a wattle and Daub cottage. These made by weaving willow wands (Wattle) to make a hurdle or wall then slapping (daubing) on clay and animal dung and straw. They are still standing today. My Family tree is hard to follow as the males were all called John or Walter… except of course Uncle Eli. 😀
          I grew up where a “Volcano” dominated the flat land. Everyone then thought it was and so as a child I believed. I was so disappointed to find out it is actually a limestone outlier from the Mendip hills the “Crater” at the top being an iron age or earlier fortification.

          • Actually, I am a canibal.
            Swedes mashed up are actually way more tasty than given credit. Trick is to cook them in beef broth instead of salted water. And when you mash them drop in a sizeable chunk of butter. Goes with any sort of meat.

            Also, the carbohydrates in them are slower than in a potato.

          • German, Scott, and Irish by decent… with just enough Choctaw to make one half of the family try to kill the other half roughly a hundred years or so ago. (there was a dispute over maternal lineage)

            Amplify the behavioral quirks of each group… that’s me. (predominantly German from my father’s side of the family. He was drafted for WW-II, and then tossed into the stockade when the issue of whether he was born in Canada or the US came up. He was 2nd generation German.)

            • Every individual in a family tree has a tale to tell. Enough drama in everyone’s family history to make a Hollywood epic. One of my wishes is that I can meet my ancestors in the hereafter and listen to their stories….. there again I suppose it depends if we ended up in the same department, heaven, hell or purgatory 😀

            • Carl just noticed this- I am both Hatfield and McCoy. Hatfield on Mom’s side (Gr.Granpa Ted H. was from that part of West. Va. and married the daughter of a railroad conductor and moved west to become a Cowboy on the St.Clair ranch in NW Kansas-He was killed by a tornado- after surviving the Civil War and the unpleasantness with the McCoy’s . The McCoys of my family left the Tug
              river Country of Kentucky Before the Civil War. They settled in Iowa and became farmers. Gr. Granpa McCoy was a Artillery officer in an Iowa regiment of the Union army. He got out, went home to farm and got a Mail-Order bride from Scotland- who was some 25 years his junior.
              So when someone says “let’s not fight like the Hatfields and McCoys.” I reply: “Being both Hatfiled and McCoy-they eventually got along somehow…” 😉
              Now we are a tourist attraction:
              http://www.tourpikecounty.com/index.php?page=hatfields-and-mccoys
              My Cousin runs a pub in Pike County called the “Real McCoy”…

            • @Carl. All I know for certain is that they did not get along at all, and that at some point, part of the family packed up and moved to the other end of the county overnight. That was the group that I am from. “Wild Bill” Sullivan, a common ancestor, was known for being a bit “unmanagable”

    • Hi

      Nice article Karen

      As for the accent thing, I’ll keep that in my bookmarks to show to some english “teachers” over here. As you may know, the French mastery of the english language is deemed quite poor (by ourselves at least). One of the main problems (from my point of vue at least) is that the aformentioned english teachers insist all the time upon having “a nice english accent” (sorry here for the Scots, Welsh, Irish….people). Wake up guys, this does not exist…..and stop explaining all the time that we need to learn progressive plu perfect, cos you’ll never use it !

      I had some funny times when I was a trainee engineer on the BP chemical plant in Grangemouth. The accent was really hard to get at the beginning (what is a “foon call”/ Phone call ?), but when I got back home it payed off.

      And well done Andy lad !

  12. A bit of somewhat on topic…. for the title of the post.

    A while back, I noted the three large calderas in SE Spain. While digging up info on them, the best reference was exploring why only one of the calderas was mineralized. In other words, why it had concentrations of valuble metals while the other two calderas did not.

    The conclusion from the paper was that the lack of hydrothermal fluid circulation was the reason.

    Went in and looked around to find the referece. It should be listed in Ruminarian III – Holey Musings (calderas) You will also find my volume estimate formula for the material coming out of the hole, based on the size of the hole. Remember that not all caldera events are massive eruptions. Many are peicemeal and the caldera forms later as the roof sags or falls in. (collapse caldera) This can be a few minutes to several decades.

    • I would still however argue that piecemeal calderas are less common than those associated with huge eruptions.

    • Ruminating a bit more: a collapse caldera might not be representative of the amount of lava etc emitted; it would “just” be the area where the roof of the magma chamber subsided. 😕

      • Actually that is a very good point.
        Askja for instance did only loose a small portion of her magma chamber when she subsided.

      • … with regards to the piecemeal idea. As material is removed from the chamber, less and less support for the roof eventually causes it to structurally fail.

        From the evaluated data, where a listed volume of ejecta was published vs the dimensions of the caldera, I came up with a correlation coefficient of 0.891470429364. Std Error about the line was 0.689818420719. For locations where I have used this formula against proposed caldera like structures, no specific eruptive volume was located in published materials, and the size of them point to it being a large amount of material. The only way I can assume that the formula to hold valid in such a case would be for the eruption and caldera formation to have been a series of less than catastrophic eruptions that lead to the evacuation of a chamber, which then subsided into the vacant space after the roof was no longer able to support itself.

        And of course, the usual Caveat. Not a Geologist, not a mortician, and I haven’t been able to grow a decent tomato in 5 years.

  13. Okay, it would happen sometime…

    Seems like we have a serial earthquake. Can a large earthquake trigger another large earthquake at another faultline? The normal answer is no. People have though been bending their buttocks in all directions to try to prove this, but without a really good example.
    Papua New Guinea just gave us one.
    First there was a 7,2M earthquake over at the New Ireland Region part of the pacific faultline (where the pacific oceanic crust gets pushed under PNG) at 383 km depth.
    1 hour 55 minutes later a 6.8M earthquake popped under the New England Region where Australia is slamming into PNG at 80 km depth. A totally different faultline with at totally different dynamics.

    So, it seems like earthquakes sometimes can cause another earthquake at a different faultline if the other faultline is close enough.

    Sad part is that all the goofballs will know have an example to pester us with. They will say that if it happened here a japanese earthquake will be responsible for a Californian one a week later. Sigh…

    And, my thoughts for those who died in the earthquakes.

    • Could this have been a fluke? Well, it is possible, but it is also within both an acceptable timeframe and within an acceptable distance for the size of the initial earthquake.

    • I still hold that stress fields have to propagate to the new region in order for there to be an effect. Neighboring fault systems I can easily see this happening, but if the other fault system is on the opposite end of a large plate, I would think that the stress field would have a lot of area to be distributed in. And that would diminish the effect, and lessen the likelihood of being able to point to it and hop up and down.

      • I totally agree with you.
        And here the distance was short enough for the stress field to be able to propagate that far. I would have loved to have seen the smaller earthquakes in the pre and after phase for the initial quake.
        Cool though to have seen one that is probably a case of serial earthquake. I am very happy it did not happen in december 2012…

        • TOOOT (Totally off or on Topic) Carl ..
          hint .. hint ..
          look up at the Bunga up north …
          *BTW was expecting a Laki post, … eh ?*

          • Sorry, got hit with a bundle of things to do and very little time to do it. There will be one soon, but soon is going to be after tuesday (have a deadline to meet).

            • Ah, deadlines are serious! You are completely forgiven, no one wants a dead or semi dead blogger anyway, do they ? – If passin a deadline, one risks mortality (eh, right?, English speaking crowd). I will look after them Icelandic mountains (and their native trolls) so they do not do any foolish untill next Laki installment 😉
              On otherhand if Laki itself begins of its own, then we need no Laki installment!
              *never been prophetic*

            • I hate troll bridges….

              … but on a plus side, I have porcured manpower to help me with that @#%$@% @#$@#$ peice of equipment tomorrow. But it’s projected to rain. That makes it fun… I guess. If you are into that sort of thing.

            • Yepp, this is one of them serious ones.
              But, my life is not on the line. But, if I am not finnished before tuesday 15.00 I will get a hefty fine for not handing in this years fiscal report on time.

            • Ah, my simpathies 😉
              *possible bad quality Hekla quake, 11 km SW of it, this morning. A rather haft one in Godabunga. All is normal on strain charts in my Kingdon of Island*

    • It’s possible. The area has been comparatively quiet (for that part of the world) so stress may have built up, which could make it “easier” for one earthquake to set off another one 😕

  14. As I have noted, circulating hydrothermal fluids seem to be key in the mineralization of geologic structures. We (for the most part) are aware of travertine deposits, but what I found while poking around wikipedia, is that silica can be disolved in water, and can make ultra pure deposits of quartz. This fits with the idea of gold showing up in quartz bearing rock.

    • Hi

      Silica solubility is around 100 mg/l at “normal” pH. If you lower or augment the pH solubility will rise (more on the alkaline side). High temperature will help too. However, silica scale is really difficult to clean. Do not forget that Silica and so quartz is a really very common mineral.

    • There is another key too for mineralization in geologic structures and that happens in lava tubes. At the surface of a long lasting lava tube all sorts of goodies will deposit that have a high solidus point. Take for instance the Norilsk deposit, it is the tube walls they are digging up there.
      Same of course goes for the magmatic plumbing system in the volcanoes themselves.

    • Why the interest? A few days ago, Carl was Be-Bopping his way through a paper and ran across a hint, an inference, that the Icelandic Plume was at a incipient or formative stage. If so, then it would not be the Alpha Plume, and could, over time, be getting more energetic.

      Sure, Iceland and the Atlantic LIP have been around for a few million years, but no one has a real good handle on how long these things last. Well, some may, but it’s not part of general knowledge.

      I’m no good at Rayleigh-Taylor instability, so someone with the cajoles to tackle it may have to step up to the plate.

      • Interesting, Lurk, Iceland is just beginning. We look at things on human time scales. -I tend to
        look at my own neighboring plume- Yellowstone – as slowing down.. To the dismay of Yellowstone
        Mongers Here is a good page on the Yellowstone system:
        http://www.virtualuppermantle.info/Yellowstone.htm
        Now to find that paper i read about the slowing system.

    • Yellowstone is part of the Columbia River – Snake River Plain – Yellowstone mafic large igneous province. It has had silicic activity: rhyolitic ignimbrite, lava, pyroclastic fallout and surge deposits.

  15. Well, the thinking from some of the “easily excitable”… is that large nuclear tests could have caused “landslides” along the CMB debris that could be starting to manifest themselves as regions where fingers of freshly heated mantle are beginning to well up and make their way to the surface.

    Personally, I don’t put a whole lot of stock in that idea, though it seems more plausible than a red dwarf slinging in past the inner solar system every 3600 years.

    Spooky mental exercise none the less. I’m pretty sure that seismic analysis would pick off any oddball slow wave areas… provided that they could get the resolution. (tomography).

    As noted previously, I have no functional ability with regards to Rayleigh-Taylor convection. Thats the sort of mechanism that I would expect to be in play if this were real.

    It might very well be related to local geomagnetic excursions… and would fit with the coincidental volcanism that seems to have accompanied the Laschamp event

    Previously I had counted it as evidence of a stirred up asthenosphere from a diving/detaching plate… which is still quite possible.

    • Yeah… well…

      For the “easily excitable” out there, take this from someone who has worked with and developed outlandish weapons. The idea of an underground test doing this is just so stupendously uninformed that there is no word for it.

      There has never in the history of mankind been built a nuclear device that powerful. End of story.
      The power it takes to do that you need more power then exists in all thermonuclear bombs ever built being detonated in the same spot.
      The “easily excitable” always over rate the power of a nuke compared to nature. The planet earth and its crust does not notice that little energy.

      For friggs sake, Krakatau exploded with more force than all nukes ever built. And the force leading up to the explotion was orders of magnitude beyond the actual explosion. And the power behind Yellowstone is 2 orders of magnitude larger than at Krakatau.

      Or in other words… The power every 4 seconds from the Grimsvötn 2011 eruption equals to an American tactical MIRV 700Kt thermonuclear device detonating. Need it even simpler? Well that is 13 Tzar Bomba per hour (50Mt/largest nuke ever detonated). And Grimsvötn was just a large VEI-4 to small VEI-5 eruption. Now, do the logical thing and ponder what a piddly nuke would do with a VEI-8 volcano. The answer is simple, it would do absolutely nothing.

    • Perhaps the largest glaring issue for the “excitable ones” is from the article itself:

      “The evidence suggests that the Chicxulub crater was made by a vertical impact,” Muller says. Unlike an oblique impact, a vertical impact would cause no shear forces at the CMB, thus no large CMB avalanches and no disruption of the geodynamo.

      On the other hand, a powerful oblique impact could strip most of the CMB of its insulating sediments. This would be followed not only by enormous flood basalts but also by a very long period during which there were no magnetic field reversals at all, because not enough sediment had accumulated for avalanches to occur and trigger them.

      And a nuclear blast, detonated at pretty much any depth, is going to consist of a single impulse wave traveling straight down, much like a diminutive meteor impact with vertical orientation. Off to one side, this pressure wave will track like pretty much any P-Wave. And that is assuming. (warning, be careful when you assume) that the wave looses no power as it propagates. I’m pretty sure that the energy in that wave will drop at an R2 rate the further from the point source.

      • “And a nuclear blast, detonated at pretty much any depth, is going to consist of a single impulse wave traveling straight down”

        No, it will not. It will be an omnidirectional blast (if underground) that will reflect at the crust/aerial boundary and at the MOHO. Wave fronts hate transitioning from one media to another.

        A meteor blast on the other hand is directional force.

        Let us say that you have 2 sticks of dynamite. One you put on the ground and blast off, one you put into a pistongun and then you point the piston towards the ground. The pistongun is the meteor at vertical impact. The other is a nuke. The pistongun will put a heck of a lot of energy down into the ground because the energy is delivered in a directional form. The other omnidirectional will not.

        Another way of seeing it (below ground) is that a jackhammer will use a lot less energy to crush a cubic meter of rock in a mine then what is used in a mining blast, for the same reasons of directionality. On the other hand only a madman would use a jackhammer for the job since it takes such a long time to do the job that it is a loss anyhow.

        I might though have misunderstod you completely 🙂

        And yepp, it will R2 out of existance fairly fast.

        Chixcolub is fun, I knew that the “Excitables” use that, but I did not know that they thought it was even remotely comparable to a nuke. Once again they do not understand the difference between a piddly little nuke at natures shear awesomeness. I wonder who will try to say that a nuke is equal to a supernova, someone is bound to sooner or later 🙂

        • No, you understood me pretty well. I discounted the reflected wave and only thought along the lines of “far field.” Natch “near field” effects will set up an interference pattern in the wavefront.

          I stand corrected on the details. 😀

          • After 16 hours of fiscal reporting I am a bit vague in the head… So if I understood anything it is a miracle of biblical proportions since I just been hit by the type of stone tablets that only a tax authority could dream up.

        • I wonder who will try to say that a nuke is equal to a supernova, someone is bound to sooner or later

          I’ll do it. The venerable Chevy Nova with it’s limited truck space, is going to take quite a compact device in order to shoehorn a thermonuclear device into it. If successful, I would refer to this as a Super… Nova. That is if you can get over the ¡no va! aspect of it.

          I drove it’s Pontiac version for a while. The Ventura. (“strait six” is not what one would call a performance engine… the design is more suited for pulling stumps) The other GM version was the Oldsmobile Omega. I’m pretty sure it was the “omega” for many people, being the last Oldsmobile they would ever tolerate owning…

          The cool thing about the model is that you can shove a lot of stuff under the hood.

          This could probably be called a Super Nova. It has a twin turbocharged LS2 engine. (intended for a Corvette) and a crap load of horsepower.

          • Oh my…
            I grew up in one of those. It was converted here into an Opel (GM). We had the station waggoon model of them, large ass car. My mother used to joke and say that it took that six 50 km to get up unto speed, but when it had reached the speed it coasted for another 50 km.
            Once an old Fiat came infront of the car, it got a bump on the fender. The Fiat was a write off.

          • I actually hit a drunk pedestrian with one of them. As you know, they were very springy. Had just left the light and crossed the intersection, the next thing I knew I saw what appeared to be two marshmallows bouncing up and down in my headlights. It was the pastey white skin on the back of her legs that blended quite well with the fog. I locked em up and slid to a stop, somewhat diagonal in the road. She had her arm out to block the impact. Had she not done that, I never would have touched her. The sway from the springs transfered enough momentum up her stiff arm to knock her over to the side of the road. The police cited her for the accident. And yes, they did measure the skidmarks… I was below the speed limit by half. She refused transport to the hospital and was damned near arrested for drunk in public. All she sustained was a small cut on the back of her head when she hit the ground. Her son pulled up and gave her a ride home.

            To this day, I curse pedestrians I see walking down the side of the road, in the dark, wearing black or dark clothing. Farking idiots.

            • Had a 4th grade teacher who had a ’64 Nova SS convertible! (Like my auntie Arlene who had
              a Olds Cutlass 442) They were the living embodiment of the “little old lady from Pasadena”.
              That Cutlass was the only Olds I ever wanted..

  16. Ref the @#$@% equipment move. Successfully completed, though I spent the entire night flopping around in bed worrying about it. I may have popped a gasket on my grandson, but a few days in the shop and he will be right as rain. 😀

    Previously, I have surfed off the back of the truck with one of these things and they are not pretty when they hit the ground. They make their own breccia field.

  17. Hi

    I’ve made a density plot for El Hierro using data from April 04 to today 08/07 (by the way there was a 3.1 today).

    I’ve played a bit with the mesh resolution, because I know from experience that this snippet of code can produce some artefacts (I’m using a contour function, a bit like making altitude curves on a map but here it is a number of earthquakes per area unit). You can find another video with a tighter mesh on YT and see the difference by yourelves.

    I think thre are 2 interesting points on this video. The first one we can see on the left lf the picture with an east pointing crescent. It could be the effects of the previous intrusion cooling.

    The second one is the bright zone (meaning a high density of quakes) not far from under the Tanganasoga zone. This is more meaningful to my mind as the density is rising in that location since a few days. Maybe this show some reactivation to come. Only time will tell.

    On the title bar you can see the start and actual date, and the mesh resolution.
    The color bar shows earthquake density.

    • Interesting, thank you.

      Here are P waves with no S waves, which I am working on: http://oi41.tinypic.com/2rxta37.jpg

      UKV edit: your posts are still going to the dungeon – not sure why. Hope they are all resurrected now

      Edit: Now even the released ones are going back into the Dungeon. This is ridiculous. Anyone with any idea? To the rest of the Dragons, try to check often for the next few days so Karen is not lost in the Dungeons, after a while Akizmet should learn. /Carl

    • My comment got lost?

      Interesting, thank you 🙂

      Here are P waves with no S waves to 06/06/2013 , which I am working on.

      • I wonder why you end up in the nether regions ?
        As to the graph what is your intent ? Showing zones with no S waves meaning where there is liquid ?

        • No idea why I ended up the dungeons 😕

          Re S waves – dunno that you can be that prescriptive. No S waves means that the S wave did not make it to the receiving station so there may be something between the origin and the receiving station which prevents the S wave from getting through or for some reason the receiving station failed to detect the S wave. Liquid is one option.

          • That was just a question. In fact when I used the master data to do some plots of VS and VP last year I removed the quakes missing the S waves. So your point of vue is interesting hence my question.

          • Back in the vaults again … I will try and establish why this is happening … have you been very wicked … grinning!

            • Sadly, not 😦

              rescued by dfm

              I do not know what’s putting you in the gaols. Some more experienced draconid could maybe help you….

            • In the dungeon again! Is someone trying to tell me something 😕 A girl could get a complex 😉

              rescued by dfm

  18. Hi

    There a small swarm going on on El Hierro with 7 quakes since this morning. I’ll do a replot today to see is there is a trend.

  19. OT story….

    While inport Bahrain, our liberty launches put into and tied up at a barge along the pier. On this barge, was a large shelter for the security detail to stand watch in. Behind the shelter, was a small “privy” that consisted of a piece of plate steel with a circular hole cut into it…. No catch basin, it went strait to the bay.

    One night, as the crew was returning from liberty, one of the female crew members went around back to use the privy. We heard a screech and a splash. Sure enough, she had fallen through the hole. We fished her out of the water and sent her back to the ship so that the medical staff could take care of her injuries. (she picked up a few scrapes as she went through the hole).

    I mention this because as I was telling the story to my wife, I had used it as an example of Karma. This particular person was, (from her mannerisms) God’s gift to mankind. It just goes to prove that you should never get too stuck on yourself. Karma will get ya.

  20. OT of possible interest to Geolurking, Carl and others…

    In south Iceland we see 2 rift volcanic zones, one in the west (WVZ) and one in the east (EVZ). The west includes Reykjanes, Krisuvik, Hengill. The east includes Hekla, Katla, dead zone.

    This paper describes something very interesting to a discussion here at the cafe 🙂
    http://jardvis.hi.is/sites/jardvis.hi.is/files/Pdf_skjol/Jokull58_pdf/jokull58-einarsson.pdf
    Hreppar microplate is the tectonic piece between Hengill, Hekla, SISZ and Langjokull. Volcanism is extinct and there is no earthquake activity here. This is where I live 🙂

    “The question is whether the ridge jump occurs by rift propagation,i.e. the EVZ propagating towards the SW [Westman Islands] while the WVZ recedes, or by activity alternating between the rifts (Sigmundsson et al., 1995) and the whole WVZ gradually becoming less active. The lack of evidence for rotated structures within the Hreppar Microplate has been evoked to support the latter hypothesis.
    Recent modeling studies of GPS data, however, appear to support rotational movements of the Hreppar Microplate (La Femina et al., 2005), which is in favour of the propagating rift hypothesis. The model results indicate that near the Hengill triple junction as much as 35% of the plate movements is taken up by the WVZ. This proportion dies out towards the NE and is less than 10% in the Langjökull region. This must indicate a counter-clockwise rotation of the Hreppar”

  21. Evening

    I’m wondering if the 3.1 quake of yesterday and the subsequent little swarm up under the island are not a small reactivation. Time will tell.

    Here are 3 videos to make our mind.

    On the first one (3D view) note the cluster at the very end of the video (zoom part)

    For the density plot I made 2 passes, one with a “floating” colorbar value (colorbar is set along the max of the day shown) and the second one with the max value at the end of the sequence).
    One can see that the “contour” function is quite tricky. However the cluster under the island is stringer than yesterday.

    For the subplots video I think that it is the top left view (from the south) which shows best the evolution.

    enjoy !

    • Thank you from the dungeon.

      Edit: I do not have a clue why this is happening. It is like the entire WP environment is attacking you. /Carl

  22. Could I kindly ask every Dragon to keep a watchful eye out for Karen who seems to get stuck ridiculously often in the Dungeon. And Karen, please keep up the commenting. The more times we release you the faster Akizmet will learn that you are a good person.

    Karen, I am terribly sorry for this.

  23. ROFL!!!
    According to the fulley automated system at IMO there was a 11M earthquake outside of Flatöy around 19.26.

    Just to put it to perspective. It would have moved Iceland a couple of kilometers and been as destructive in London as 9M quake at ground zero.

    • For strike-slip, I came up with about 20 km max displacement. Average of 3.8 km displacement along a really, really long surface rupture. “globe splitting” would be appropriate, ‘cuz that is what it would look like. (it wouldn’t actually split it, but you would think so after riding that one. In excess of 193.1% g acceleration for everything within 250 km radius of the epicenter. If you were in a structure that could withstand it, you would literally be bounced back and forth off of the walls… you know how they say to not shake your packages before opening them? You would be the fragile ceramic inside.)

  24. Testing to see whether I am going to spend another day in the dungeon.

    BTW this started when I posted the Tinypic image. Is the image OK?
    Rescued by Spica
    I have no idea why it started, hopefully our spambot will learn that Karen´s comments are most certainly not spam.

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