Renewed activity at El Hierro

VC-commenters arjanmm and Alison noted at 14:54 and 14:59 UTC today that some tremor was going on at our famous Canarian friend El Hierro. A clear rise in tremor, combined with several earthquakes were seen at the seismic stations on El Hierro, most notably on the CHIE-station.

The tremor and EQ’s seen at the CHIE-station. Image by IGN.

Another view of the onset of the tremor and quakes. Image by IGN.

Diario El Hierro (the local newspaper) has already posted a news item about the renewed activity on their island, stating that “an important seismic reactivation” has occurred at their volcano. They state that up to now, 30 earthquakes between M1.9 and M2.6 have been measured, making this a significant reactivation event indeed. A quick look on the list of EQ’s published by the IGN tells that so far (19:00 UTC) 55-60 EQ’s between M1.7 and M2.7 have been detected.

The locations of the earthquakes. Image by IGN.

dfm has been very quick in 3D-plotting the renewed activity as well, as can be seen below. Thanks for that dfm and others!

Image by VC-commenter dfm

Whether this new activity will lead to a baby brother or sister of Bob will remain to be seen, but it is sure that something is on the move again deep below El Hierro. As we have seen with the birth of Bob, there don’t need to be many shallow quakes in an area for a new fissure to open and allow the lava to erupt, whether this is on the seabed or not.

We should definitely keep an eye on what is happening, since the combined knowledge of all commenters and the powers of data processing by some of them, can surely help in painting a picture of what is actually going on, even though official sources might sometimes disagree. In Bobs case, several commenters have had a better grip of the reality at times than official sources, so don’t be afraid to speak out if you think you have found something important.

And finally, a short note to all readers and commenters; try not to swamp the IGN website or any other site that locals might need to get the information they need. If possible, quote text and provide the source, and upload images and post the link to the uploaded image instead of linking directly to the source to prevent overloading of those websites. With that in mind, please don’t forget VC’s special section about Bob/El Hierro:

El Nathan

138 thoughts on “Renewed activity at El Hierro

  1. Thanks El Nathan. A good reminder about not overloading the IGN website. I have already noticed it is slower to update.

    • Might be artefactual – there was a big corona eruption arrived last night with pronounced aurora.

  2. If this continues I hope the web cams come back into action. I miss looking at the sea, not just the volcanoes .I just liked a morning visit to somewhere warm.
    My thoughts with all on El Hierro.

    • CHIE looks like a “chugging” episode – which is what we had, was it in 2011?, before the harmonic tremor started. I’m with Diana on missing the sea picture! 🙂

      • No, no chugging before Bob started. Just the onset of tremor and a “Hey, did anybody notice?”

        I’m currently stuck on an AF Base waiting until I can take a server down. Yee Haw.

          • It is… but it has its own entertainment. I just saw someone “mashing” a formation. They had them down doing push ups. Someone must have messed up.

          • Brings back memories. Way back, I took a class out on the grinder and marched them around until they fessed up and told me who broke the chalkboard in the classroom. Once they did, I broke them for lunch, all I did was to tell the one responsible “No horseplay in the classroom”

            The object lesson for the class was “Don’t lie to your Chief”

  3. I’ve been looking for the recent GPS data for El Hierro but can’t seem to find it, only old data. Has anyone got the url please.

  4. Hi
    I’ve waited a bit since the data was updating quite fast, but here are the results

    Today there was a renewal of the seismic activity with the apparition of a distinct tremor during the afternoon.

    Here is a plot for the earthquakes of march with the latest (at 17h39 UTC) available data.

    For the time being the activity is mainly under the Moho with the deeper quakes at 30 something kms (I stopped at -25) but there were also a few quakes over the Moho.

    What can be seen is that the locations for the new quakes are in areas previously not very active, so this could mean as we have seen before that there is a new bolus of magma coming up.
    The cyan dots are all the sites of previous earthquakes from July 2011 to Febreuary 2013.

    This video is divided in 3 parts :

    – first part is a day to day update for the quakes, with size according to magnitude (see mag scale at the bottom of the plot) and color according to date (see left side of the colorbar). Terrain elevation is also shown (see right side of the CB).
    – second part is a 360 ° rotation with some “rocking chair” effect and a vertical rotation.
    – third part is a zoom on the last quake zone

    Seismic data is from IGN, Terrain data from NOAA, made on GNU Octave

    • Involcan (unluckily in a scientific workshop in Berkeley) indicate that the signal is NOT a tremor signal. There should be some sign of rupture mechnisms which apparently are not present. Some people on Avcan indicate that the quake mag 3 was felt in Mocanal.

    • Good evening everyone, how exciting, little Bob is stirring again??? I saw this on the local El Hierro newspaper report – translated with the help of
      Google….I am wondering, like a lot of you if the web cams might be reinstated…

      “The island of El Hierro posted up until 18:12 hours on Monday, March 18, a total of 76 earthquakes. The largest of those registered so far has been of 3.1 magnitude on Richter scale. So far, none of the earthquakes have been felt by the population.

      The continuous succession of earthquakes, sometimes several of them every 2 or 3 minutes, has not yet been felt by the population, as recorded in the IGN website. The depth at which earthquakes are occurring between 30 and 12 kilometers.

      Although there have been tremors of 3.0 and 3.1 magnitude on the Richter scale, the National Geographic Institute (IGN), for now, no way they have been collected.

      From 14:25 hours today (the first two earthquakes were recorded Monday, one bit after 00:00 pm and the second at 06:01 hours), the number of earthquakes has been increasing exponentially , resulting in many cases a succession of small earthquakes every two or three minutes and so for hours. The largest of the earthquakes recorded so far has been of 3.1 magnitude on the Richter scale.

      Meanwhile, IGN says that what they are detecting on El Hierro “is very similar to what we saw in the months of June, September and December, which is a very seismically active earthquake followed where some overlap with others.”

      This is a seismic swarm and so far, the IGN is not aware yet of deformity, or emission of gases that would determine the essential signals that a volcanic eruption”

      • I have seen National Geographic, or could have been Discovery TV programmes about the Cascadia fault. A very scary scenario indeed. Glad to hear you would be relatively unaffected tgmmcoy.

        • I lived on the Oregon coast and was never comfortable since this scenario was proposed. We know a Tu-tu Tun Indian who said her people had many stories of the
          the “Day of the Earth Shaking and the Great Waters..””_JUST BEFORE THE
          WHITE MAN ARRIVED_ in great numbers.. The T-Tuns as she said, had instructions
          on how to respond to a Quake. They had different scenarios if the quake shook North
          /South or East/West- which i recall was the one to bail to the hills as rapidly as possible…
          I am thankful for the several Gigatons of Basalt we live on now…
          here is a bit on the Tututuni’s Tiny-her given name- is one of four full blood members of the tribe left.

    • I hate articles like this.

      Seismic experts say another monster quake and tsunami are overdue.

      Pardon my severity… but Bullshit! What experts? Personally, I think that Jay Wilson, the chairman for the Communion that wrote the report, was misrepresented by the mealy mouthed reporter.

      He stated: “we’re well within the window for it to happen again”, not that it is “overdue.”

      Being “in a window” is an speaks of a time period within which, over the entire history, you can expect something to happen with a percentage of events those falling in that window.

      It all boils down to the nefarious Gaussian distribution. The one that Nicholas Taleb abhors due to it being over relied upon.

      Try this on for size.

      As promised, the updated plot.
      As a bonus, the average bust size for this “idealized” population is 34.81. (34.48 to 35.14 with 99% confidence). So, if you run across someone who has it stuck in their head that augmentation is needed, you might point out that it’s not the most sought after thing in popular culture.

      This is a plot of the heights of women that commonly appear on TV, Movies, Playboy etc. This plot is not going to be representative of all women, these are the ones who got famous and noted for some reason or another. These are women that audiences (most likely, male audiences) tend to prefer. That means that the sample population is biased towards that criteria. The peak of the red curve is about 164.4803 cm, that is the average of the group.

      The Red curve is the Normal Distribution (Gaussian) and the Blue curve is the Cumulative Density Curve for it. Pick a spot on the blue curve and read the percentage on the right. That is the percentage of the population (represented by the curve) that will be that height or less.

      Heidi Klum and Olivia Newton John’s positions on the curve are noted for reference.

      Now… pick your favorite female star or person… find out their height (in cm). You may find some really tall ones, or you may find some pretty short ones. Do they look that abnormal to you? Your preference may be for tall or short women, and you will probably find more of that type. But over all, they will tend to this curve. Randomly picking one will NOT guarantee that she will be in any particular position on the curve. (Heidi Klum is taller than about 90% of her also famous cohorts)

      Likewise, just because you have a return interval that averages about 300 years, does not mean that it will happen. Just that on average, it works out to that amount of time.

      Earthquakes and Volcanoes DO NOT FOLLOW SCHEDULES

      BTW, muy wife was over 182.88 cm when I married her. She has shrank since then. (this tends to piss her off so I generally don’t mention it to her)

      • Yep,I agree, Lurk as the problem is lack of preparedness for the infrastructure.
        sooner or later it will whack the coast and I dare say no one will be any more
        prepared than now. No efforts to even marginally reinforce structures, bridges,
        and if you do, turf battles ensue. My main gripe is that people will have to die before anything is really done.The IT COULD HAPPEN TOMORROW aspect does a disservice to the subject matter….

        • ROFLOL! Thanks for pointing that out. 😀

          It was a long day. I can re-do it in inches… which I will probably do anyway. In essence, I did the conversion backwards.

          I blame too much elevator music while on hold. Even through I was being paid to listen to it.

          She was 6 feet tall, towering over me by 2″. now she doesn’t.

          And why on Gods green earth would you name a kid Aurea. (something to that effect) Even though the new grandkid is gonna be a girl, what is wrong with Rebeca or Susan?

          I think I may just call her “Poot” after the dog. (relax, my cousins nickname was tizzard.) I called her soon to be cousin (has to be born yet) “Dooser,” because like the Doosers on Fraggle Rock, he just wouldn’t quit crying. That kid had a set of lungs on him like you would not believe. On second though… maybe “poot” is a bad idea.

      • She shouldn’t get pissed off about it though, since every day she moves closer to the sweet spot for being a woman who is famous because of her looks.

        • I guess that is one way of looking at it. But when a woman gets on a rant about aging, good luck at convincing her otherwise. The best bet is to keep her encouraged at reading the newspaper regularly. If she gets pissed at the idiocy in the local government, she doesn’t have time to mope about aging. Yeah, it’s psyops, but its for a good purpose. (plus reading keeps the mind active than the pablum of TV)

      • It all boils down to the nefarious Gaussian distribution

        …not to mention the flagitious Poisson distribution, the heinous Pareto distribution, the discrete uniform distribution, the infamous log normal distribution, the vile exponential distribution, the atrocious Bernoulli distribution and the negative binomial distribution.

  5. WoW! Just got my first chance to check CHIE today and after first yelping “Holy S#^T!”, I thought Bob must be dancing an Irish jig a day late. How exciting. I haven’t had time to post much lately but I have been checking in. I work for an accounting firm and it is tax time here in the U. S. so I have been working, working and working some more. Too tired to do much once I get home. Even missed Etna’s beautiful show the other night.

    • Good to see you back Bobbi. Yes! This looks like the old Bob again, Nice knitting pattern, although the tremors are mostly central and to the North so we can’t really blame Bob ……yet.

      • Thanks, Diana. Yes the tremors are north of Bob, but if the lava is on the move, it has to go somewhere. We can hope it will feed little Bob and our excitement as well. 😀

    • Hi Bobbi, good to see you !

      There is something a wee bit strange about the PSD. Did you notice that the amplitude of CHIE has suddenly become very large but that is not the case with some other stations like Corc or Ctab….and previously the aplitude of the trace at CHIE was really “suppressed”. Would there have been a change is sensitivity ?

  6. And another El Hierro plot for VC 🙂
    Todays earthquakes (up to 20:30:35) are in color (yellow most recent ones).
    The question was raised whether the new activity is tectonic vs magmatic. The new swarm initiated (again, like the other swarms, same depth) quite exactly under Tanganasoga and propagates westwards. To me this seems to be a new magma injection (amateur opinion).

  7. This was posted an hour ago by INSTITUTO VOLCANOLÓGICO DE CANARIAS…

    The latest data received from the GPS station of the
    geodetic network installed in Frontera, El Hierro, Canary shows that the tendency to swelling of the island is confirmed. In the graph you can see expanded the arrow pointing the latest data, as you can see, already beginning to scale, established at a time when 12 cm.

      • Hi

        I think so also, thre’s the lower frequency part missing like you pointed out earlier. Also Involcan made a statement in spanish saying there was no tremor (yet), only rock fracturing for the moment. The guy from Involcan made an interesting parallel to a pneumatic hammer breaking rock. If I remember correctly, Carl (which I still miss a lot) kind of explained that in June if I recall correctly.

  8. A history note for ‘yall.

    El Hierro’s quakes went on for quite some time, and lined up along a mostly north south axis. They came and went over time. Always there… but not really looking like more than a dike emplacement down deep. Then the center of activity started moving south and deeper. This was pretty wild in my opinion. Quakes in a volcanic system getting ever deeper as time went on.

    From plotting Eyjafjallajökull, I was under the impression that quakes showed where the magma was moving to. Yet deeper they went the more south the center got.

    Then, with virtually no quakes to indicate it, the tremor kicked in and Bob was born south of La Restinga. It wasn’t until post processing that IGN added the quakes that happened when Bob reared his flatulent little noggin above the seafloor and started building his cute little submerged cone.

    Remember, El Hierro is a Volcano built on top of ocean sediment, that overlies Jurassic Era sediment (from when this was a basin and not an ocean) which is on top of Oceanic Crust.

    It’s a layer cake. Not all layers will snap and make a quake. Some will just ooze out of the way.

    About the hardest thing that the Jurassic Era Sediment may have, is Phyllite. The pressure isn’t really high enough to make Schist.

    For the mathematically inclined.

    Hoop Stress plays a pretty important role in all of this. For a magma intrusion to occur, it has to break out of where ever it is at, how much pressure it needs to make a quake when doing so, is determined by the hoop stress of the surrounding rock.

    I’ll leave it to the so inclined to take it from there. Me, I have been driving all day and am tired. Getting paid to sit on hold is different, but I’ll take it. With the horrible music that they play, at least I was getting paid to listen to it for a change.

    • The EQ pattern appeared to show that the magma had opted for a deeper path but what if this was a dike instrusion from a central source, which found a weaker bit of rock to break through?

      Didn’t someone say that the magma was rising at a 39 degree angle ?. Think this was in an article by Carracedo sometime back (may have been on Earthquake report or Avcan’s site).

  9. After a short calm periode whit low HT and few “large” EQ this night, has mother earth desidet to increese the activity under El Hierro again.
    Chie is updated as usual every 5 minutes, but the eq-list has not been updated the last few hours. HHas mostly been small or micro quakes, but allso som “large” (eq mag 2+)

    • I don’t think it was HT myself… after looking at the traces more focused. I think it was a set of rapid fire “poppers”

      These (as best I can figure) are the sound of rock cracking as magma forces it’s way through fresh areas.

      They have a bit of harmonic look to them, but are probably better described as “wet quakes” as Carl tended to call them… only with out the very low frequency component that we saw before.

      • Questions:
        1. Where is the point/depth of melt genesis? (the petrologists should be able to answer this.. is there anything in Stroncik’s paper?) If the “bolus” is generated from a plume of hot plastic material rising in the mantle, I think it is fair to assume the melt is created by decompression melting, i.e. it is hot enough and close enough to the surface to melt. But where does this start and how does this change the dynamics of the system? Is the melt genesis not focused on a point but phases in over the whole system. Does this create a cascade effect, with an initial (small) injection of melt triggering a wave of melt genesis throughout the system (resulting in the periods of heightened seismic activity)?
        3. What form does this melt take in its ascent? Is it a rise through a matrix of fissured mantle material? Is it a body of crystal mush where the liquid phase passes through like liquid passing a membrane (whereby “arrival” is really just a kind of pressure wave through the medium)? Is it alternatively, really one continguous body of melt that rises like a diapir in a lava lamp?
        4. If these rising bodies of magma are somehow connected, why is seismic activity occuring in different places over the course of time? Why doesn’t it take the form of a spreading center (like a cauliflower) rather than the distinct branches it actually displays?

        / I have more 😉

  10. A comment copied from Avcan on Facebook greets us this morning. Time now for coffee #2.

    ” A new intrusion of magma in El Hierro is causing a visible spasmodic tremor in the spectrogram and seismograms of the IGN. This episode begins on the last night with a train of discrete earthquakes of magnitude 2. As always in these situations, we recommend to pay attention to the directions of the authorities and report to the IGN any incident worthy of mention, as fumes or smell gas, tremors or spots in the ocean. (JR) (Translated by Bing)”

    • Sorry, I withdraw my comment – I was watching the large-scaled graph. But action is still going on strong and, as Lurking says, a vent could open unattended.

  11. There seems to be a lull in quake activity now since about 3.5 hours ago, like between 02:00 and 04:30 today. This way you can clearly see that there is no harmonic tremor, in between the discrete quakes the signal is very stable. I think that means that no magma has moved upwards towards the surface yet. Something is fracturing deep below, but it has not found an upward path yet.

    I think the image below beautifully shows that a ‘fracture wave’ has initiated yesterday, and it spread laterally towards the west-southwest. Would be great to see this pattern of the last 2 days in a slow animation, you can probably even see the ‘wave front’ moving.

    • Hi here is the update, with data up to 10h57 UTC.

      I’ll do a moving plot (eq by eq) later, but I need to tweak my code a little….as I had supressed this function to get a “day by day” animation….but you’re right it should show something.

    • The ‘fracture wave’ starts rather diffuse then becomes more focussed later, all at roughly same depth. For a magma diapir adding itself to the sysyem I think I’d have expected the opposite : a focus spreading outwards and becoming less concentrated.

      • That’s exactly what I think too. I can’t really make head or tail of the pattern. If we assume the arrival of new melt changes the far field stress pattern, then you could get distal fracturing without the immediate presence of magma and then, once the field settles, more focused activity at the location where the magma arrives… maybe.. bit far-fetched but I can’t think of anything better.

  12. Afternoon all, just catching up with the comments on Avcan’s FB page.. Elsa M Guadarrama, who I think lives on the Island is reporting (within last hour) that the vibrations are stronger and she has feelings of instability, does this mean quakes?

    She is also reporting that dogs are howling & chicken/roosters are singing more than usual. Someone replied to her asking if there is a rebellion at the farm lol, anyways, she says that nature seems more crazy than usual.

    She has noticed that the Involcan helicopter has been up a few times, especially within the last hour or so….

    Someone asked her this question: (Translated) “Notes greater vibration now Elsa, or they are swipes, as upward?”
    “It vibrates sporadically and in turn give jumps up and with that distant thunder”

    Avcan FB Page:

    Other residents are starting to post saying that Vibrations seem to be getting stronger also…Those poor Islanders. Will post more updates later 🙂

  13. Latest update (2 Mins Ago) from Involcan:

    As we already announced in yesterday, analyses that were performed seismic signals we put on the track that this episode of rebound in activity was the most energy from June 2012. While in the episode of September 2012 the number of events greater than 2.5 degrees was 54 in four days, are now accounted for 71 in just 24 hours.

  14. Hi, the time lapse in on its way…

    I made a few changes, with a bigger active dot for the earthquake and trying to have some filling for the previous ones (not easy to do in Octave, ‘filled’ does not work, but I found a way around “sort of”. One hour to go.

  15. Evenin’ All,
    I’ve been following but haven’t had time to comment…
    Thanks Gstar for digging around factbook for us…
    So; more largeish EQs than September 2012, but less than June/July 2012 (if I remember correctly?) But heading in the general direction of the June/July swarm; and at about the same depth…Remember we had a confirmed undersea eruption near Orchilla…
    So another bolus and another try…
    Go BoB’s Big Bruv, Go!!!

  16. New Update from 2 hours ago…

    19/03/2013 – 21: 45 h kuwait (18:45 Canary – UTC) this new earthquake swarm that began yesterday in the island of el Hierro in the marine area of the Gulf opposite Sabinosa, is moving along the coast north of the island, in two large embites for the time being to the West of the island and with a front of earthquakes in direction SW, although seems to have stopped in the last hours. The process of pressurization time does not advance because the magma moves under the island by filling in new areas, but if it stops again presurizara again, causing another elemental of earthquakes, and if the magnitude increases, indicate that pressure also makes it. (Enrique from Kuwait)


  17. Here is the update up to 17h46.

    The progression is clear to see with a sort of reflux in the end.

    I have set the current earthquake bigger ( x 8 relative) and with some filling.
    The other earthquakes are also filled.
    Age of the EQ gives the color.

    If I were in Orchilla I would go look for bubbles.

    Data IGN, NOAA, made on Gnu Octave

      • Yup, I’ll keep it that way. It’s a bit greedy puter tme speaking, but I think it’s worth it and as we do not have too many events yet, it’s manageable

    • I live in an area indicated to experience MMI7 intensity. Play with the different layers to see what the effects are expected to be on various types of infrastructure. It has the ability to zoom into detailed view of your area.

    • Good tool.

      The calculations for the intensity (MMI) mostly come from work by Atkinson-Wald, which uses two basic models. California like, and non California like. California and the surrounding area tend to disapate quake energy faster than the Central-US model because of the large number of faults in the area that can take up the motion. A good start is here:

      Click to access OF09-1047.pdf

      I forget which of their papers it is, but one of them had a formula in it that took me about a week to get operating correctly in a spreadsheet. Here is how a Mag 7, 8. and 9 play out vs distance from the quake.

      Elsewhere in their papers, you can get a conversion from MMI over to peak ground acceleration.

      Where this gets scary, is when you start thinking about stuff sitting on the ground, or secured to the ground.

      All objects have inertia. To find out how much energy is trying to snap a brick wall off of it’s foundation, get the mass of the wall and work through the acceleration that the ground is trying to impart upon it. The kinetic energy value that you come up with, is what that wall is having to endure to get up to the speed that the ground is moving at. The fun part? It reverses itself as the different parts of the wave come through. So, if it is successful at getting up to the speed of the ground, just a moment later, it tries to decelerate and move in the opposite direction, as dictated by the moving ground.

      It’s no wonder that stuff falls apart.

      Side note for the plotters. This is the sort of thing you wind up doing when you get burned out chasing quakes.

  18. I have yammered in the past on various forums about the Farallon plate, and on occasion, I have mentioned the lithospheric drip where the roots of the Sierra Nevada mountains are slowly dropping back into the athenosphere. This region is near and a bit north of Los Angeles.

    Now it seems that fragments of the Farallon may still be around… and in that area.

    Current thinking has it that the drip is actually a remenant of the Farallon… the Isabella Anomaly/Drip, and that yet another sliver like microplate exists off of the Califoria Coast… the Monterey Microplate.

    And the generally better PysOg article about it.

    • if ocean slabs can break off like this as they subduct, isn’t that an indication of slab pull rather than push?

  19. Another “overdue” natural disaster: “Megafloods” caused by atmospheric rivers, narrow bands of water vapor, could drown large areas of California (and elsewhere in the world).
    What will be next? Megadroughts?

    We have some annoying Centisnowfall here in northern Germany, I wish it would go away on the first day of spring.

    • I’ve read a few historical accounts of humongous California floods. Scary stuff.

      Those large mostly dry, paved and concrete rivers are there for a reason.

  20. hangin in background, my PC has sprung … Alzhaimer … it flags “vitual memory too-low” (or loss of it ?) and occational RAM loss too (its an old one, almost fit for any museum) so might miss out if it fails altogeather : but I personally think el Hierro will blow again, these are probably the “wet quakes” precceding eruption in the central volcano or the north of it bay (sucking up magma ? as Carl pointed out) *do prepare for this islanders, more likely than not, in my opinion*

    • You can adjust the size of your virtual memory in your “control panel”, “system” settings.

      Virtual Memory is essentially a paging area on your hard disk. Windows uses it to fake having more memory than is physically installed by writing some stuff to the page file. Virtual memory is gawd awful slow compared to real memory, so if you are running a lot of stuff and your machine is bogging down… that’s why. It’s hitting the “laboriously slow” page file quite a bit.

      The other option is to not run as much stuff simultaneously, or to stay away from large programs. Virtual Memory gets you around not having enough memory.

      The downside is that if your hard disk is really packed with stuff, there may not be enough room for Windows to automatically adjust for a larger page file.

    • Hey Renato! Good to see you. I trust it is warmer in Rio than here in North West England.. How I yearn for some tropical sunshine. Your presence has just brought a small hint of this to warm my poor chilled bones :D.
      For those in other parts of the world the Londodon Weather office has forecast a possibility of a white easter. We are suffering from bitterly cold wind and snow drifts.

  21. Getting back to my favorite pasttime of wild theorizing:

    we generally assume that these seismic swarms inidicate magma pushing its way into brittle rock, i.e. a hydraulic event of a fluid under pressure fracking country rock and exploiting the resulting seams (fault propagation)

    but… maybe another mechanism is also at work. Given that a crystal mush also has some structural qualities and is at equilibrium in the stress field it finds itself in, what happens when an injection of hot magma tips this mush suddenly towards melting, i.e. there is a relatively sudden phase change from semi-solid mush to fluid?

    I imagine there are two main effects. One is the change in density between a crystal lattice and a fluid medium which will be accomodated by shifts in the surrounding stress field (earthquakes) and the second will be the movements of the fluid as it exploits the resulting cracks in the surrounding rock (as explained above). Or is the change in density so marginal as to not play any role?

  22. We have a new dragon.
    I ll leave it to him to introduce himself.
    The other active dragons right now are El Nathan, Kilgharrah, Chyphria, GeoLurking and me.
    And watch CHIE on El Hierro … something seems to be going on!

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