Edinburgh – Volcanic heart of Scotland

Image from Wikipedia. Arthurs Seat, Edinburgh.

Edinburgh – home of the Scottish Parliament, Military Tattoo, Princes Street and gardens, Scott memorial, Murrayfield, Valvona and Crolla’s food emporium, sundry pubs (!), volcanoes…Eh, volcanoes?

Surprising as it may be to some people, Edinburgh plays host to a great variety of igneous rocks. The most obvious and in our case, the most interesting, are the volcano remnants of Arthur’s Seat, and the Castle Rock. These are long extinct and date from the Lower Carboniferous, about 350 million years ago. Arthur’s Seat, the larger of these, is assumed to be the main structure, the other a subsidiary, or satellite vent. These are central pipe vents from pipe conduits, cf linear conduits as associated with fissure eruptions.

The rock of Arthur’s Seat is mainly a vent agglomerate with several crystal phyric microgabbro eruption pipes (Lions Head and Lions Haunch vents so called as at a distance the remnants resemble a lion lying down) – agglomerate being a mix of explosive block and vent collapse debris, ash and lava, whilst crystal phyric refers to the presence of some minerals present with larger crystals than the background rock. The presence of gabbro in the conduit pipes indicates these volcanoes erupted a basaltic lava, gabbro being the intrusive coarse grained equivalent to basalt being of the same mineralogical composition. (Dolerite, or Diabase to some authors, again has the same composition, but has a grain size intermediate between basalt and gabbro and is usually assigned to these rocks when found in dyke and sill intrusions). The combined vent material as mapped, gives an irregular vent of 750-1000 metres across.

Picture of pipe brecciated St Austell granite to illustrate vent agglomerate appearance; a true vent agglomerate has a much larger fragment range in both size and composition however.

Photograph by Alan C who gratiously has bestowed the rights to the Volcano café. Pipe brecciated St Austell granite

The opening picture shows the main vents of the Lions Head (left) and Lions Haunch (right) in the background, with Salisbury Crags in front; these are the quarried remains of a post volcanic episode Teschenite (olivine analcime microgabbro – analcime is a hydrous sodic zeolite mineral comparable to feldspathoids; zeolite minerals usually being associated with vesicle-filling in amygdaloidal basalt flows) sill intruded into sub-volcanic sediments of Lower Carboniferous age.

Salisbury Crags are part of a site dedicated to James Hutton, who has been called the ‘Father of Geology’. It was here that Hutton part formulated his theory of Uniformitarianism, that confounded the existing Neptunism movement that insisted the Earth dated from the biblical Great Flood, by siting the presence of a rock of obvious molten origin being intruded into sediments/volcanic rock, the sediments being just visible below the sill.

Distal from the volcano, mapping and borehole evidence shows there to be up to 250metres thickness of tuffs and lavas adjacent to the vent and in the Midlothian borehole, some 10km to the south east, approximately 70m of volcanic material was found at the horizon of the Arthurs Seat volcanics.

Castle Rock is the erosional core of a relatively small and assumed satellite volcano off Arthurs Seat, composed of microgabbro approximately 150 metres in diameter. The vent again cuts through shallow water marine sediments of Lower Carboniferous – Dinantian – age. These sediments comprise predominantly sandstones and minor shale horizons; but it should be noted that in some texts the sediments erroneously are noted as limestones, a confusion arising from the rocks of this age being assigned to the Carboniferous Limestone division.

Picture from rampantscotland.com showing Castle Rock and vent.

The reference cited here below gives an artists impression of Edinburgh with the two volcanoes superimposed along with an imaginary sea level – with a lot of imagination this image could well have been a Carboniferous equivalent of El Hierro (Arthurs Seat complete with aerial cone) and our Bob (Castle Rock)!


Image of how Edinburgh would have looked like during the “interesting times”.

More recently, during the last Ice Age, ice sheet movement has produced a classic example of a ‘crag-and-tail’ with the Castle Rock – the crag – protecting the bedded Carboniferous sediments of the Royal Mile – the tail – from ice erosion, indicating mass ice movement from the west. More recently, the ice-deepened gouge channel on the north side (Princes Street gardens) has been utilised by the railway as an ideal route through the city!

Image from Google Earth.

And finally;

Image from from http://www.irocks.com/db_pics/pics/d06-238a.jpg Mystery stone…



560 thoughts on “Edinburgh – Volcanic heart of Scotland

  1. There is a boat out circling an area above the right harbour wall, which is where the eruption cam had been focused on before dusk. It has been out there since dusk and is now on the the area where the last jacuzzi was.

  2. Otro más a las 19:46

    Another one at 19: 46 (Translated by Bing)

    20 minutes ago · Like.

    David Brito Sergio a mi me da que esa señal que tu dices es el abrir y cerrar la tapa del sismografo para comprobar los sistemas xDD porque son calcadas jejejeje pero se de a que te estas refiriendo… se nota a leguas el bajo de sensibilidad de la CHIE…. les invito a revisar un dia cualquiera del mes e ir pasando mes a mes hacia atrás en el espectrograma de la estacion CHIE… a partir de noviembre de 2010…. sorpresas sorpresas se llevaran… telesismos, sismos everywhere y una señal similar al tremor que esta ininterrumpida casi desde 2007 hasta 2010…. y si hacen lo mismo en la de la Palma y en EGOM… veran el mismo patrón…..

    Sergio to my gives me that that signal that your say is open and close the lid of the seismography to check systems xDD because they are calcadas jejejeje but is of to you you are referring… Note leagues the low sensitivity of the CHIE…. I invite you to review one day of the month and go from month to month backwards in the spectrogram of the station CHIE… from November 2010…. surprises surprises carry… telesismos, earthquakes everywhere, and a signal similar to the tremor that this unbroken nearly from 2007 until 2010…. and if do the same in the Palm and EGOM… you will see the same pattern… (Translated by Bing)

    20 minutes ago · Like · 1.

    Antonio Marquez Hernandez Un poco mas pequeño que el anterior. En la web del IGN se pueden ver. http://www.ign.es/ign/​head/​volcaSenalesAnterioresDia.d​o?nombreFichero=CHIE_2012-​03-01&estacion=CHIE&Anio=2​012&Mes=03&Dia=01

    Expand Preview
    16 minutes ago · Like · 1.

    Carmen Tirado Saura parece que ahora se desplazan los sismos hasta la zona de erupcion

    It seems that now move earthquakes to the eruption zone (Translated by Bing)

    • Sometimes it might seem that the good Lord created the babylonian confusion to provide the Google people with the opportunity of Striking it Rich!
      However Reading the glorious computerized translation above confims My firm belief that there is still fairness around!

  3. Two sismitos a while ago this afternoon, one of 2.1 and another 1.9 in the area of the mar de las Calmas, the first mas in the sea and the second just off the coast to the West of la Restinga, to more depth. (Henry)

    1129677 03/01/2012 19: 07: 52 27.6311 – 18.0587 12.4 2.1 mbLg SW EL PINAR.IHI
    1129681 03/01/2012 19: 46: 21 27.6436 – 18.0218 17.7 1.9 mbLg SW EL PINAR.IHI


    EARTHQUAKES DAY 01 MAR. -Blue clear (6)
    EARTHQUAKES DAY 29 FEB. -Red (4)
    EARTHQUAKES DAY 28 FEB. -Green course (8)
    EARTHQUAKES DAY 27 FEB. -Violet (20) – new 6
    EARTHQUAKES DAY 26 FEB. -Rosa (22) – 10 new

    If someone has felt something at these times, don’t forget to fill in the questionnaire of the IGN as it has been felt…


  4. And another one is something starting to happen ?????

    ‎1129682 01/03/2012 20:17:02 27.6503 -18.0629 14 2.0 mbLg SW EL PINAR.IHI [+] aqui el que faltaba.

  5. tres seguidos y todos por la misma zona, aunque distintas profundidades, quizás signifique nuevo aporte de magma o asentamiento, ya nos darán mas información de lo que pueden significar y lo que pueden prever con estos datos.

    three row and all for the same area, although different depths, perhaps mean new contribution of magma or settlement, and they will give us more information which may mean and what can provide these data. (Translated by Bing)

  6. Time for me to go to bed…

    And yepp, whenever a volcano do not blow, blame the woman who mentioned it 🙂

  7. Privacy google concerns, here, Facebook privacy concerns there, ACTA here, SOPA there, here goes my joke of the day.

    i realize I cannot have more cookies in my browser anymore. I am becoming diabetic.

  8. Movements are being felt again in the North of the Island.

    el de las 19:07 se sintió, leve, en Los Mocanes, Frontera
    y antes, a las 18:30, algo hizo tintinear los objetos en las estanterías.
    llenando el formulario…

    of the 19: 07 felt, mild, in Los Mocanes, border and earlier, at 6: 30, something he jingling objects on the shelves.
    by filling out the form… (Translated by Bing)

    24 minutes ago · Like ·

  9. Is there something going on at Santorini? Because today in site stats 1/3 of all searches are related to Santorini in some way, including “death count santorini nea kameni”. Anyone has any idea what if something has happened?

    • I have checked and rechecked. It has been like this for three days now…

      Yes there was some tremor a couple of days ago, but nothing to hang on the wall. Also a few quakes. But nothing otherwise. I think it is just that we have gotten a high google raiting or some such on the article on Santorini.
      Ismosav has no data on anything going on… I am stumped really.

    • And also, if it even had a hiccup I bet Luisport would be in here through the doors within seconds 🙂

      • I think that google did it’s crawl, gave the post a high ranking.
        Because that post is linked to from a lot of sites back when that unrelated quake swarm was. So, it is all down to the mysterious ways of google 🙂

  10. Just to be on the right side here, I did not mean that everyone that does not have a job is lazy, but I know a few of them, so I know that there is some of them too. Oneof the parties here in Norway, made a suggestion once – saying that all people that were applying for social wellfare (Not disability money) were to come down before 9 o’clock, everyday, to report that they are searching for jobs. I think that it could work. But then again, what do I know 😉

    • I read your comment a short while ago and I didn’t think you were saying that.

      Having said that there always have and always will be people who are claiming the benefits without looking for work, and those who don’t want to work because they get more money signing on (in this country anyway). Then there are those who are both working and claiming unemployement benefits. Its always been that way and they are the people that give ‘unemployed’ a bad name, even if they are the minority.

      • Thank you. I’m not too good at explaining,so it’s great that people like Jenny will explain it even further, so people can understand what I mean without megetting misunderstood 😛

  11. Another thing. WTF is going on with all the earthquakes everywhere these days? Is it more than normal? Or is it people paying too much attention to this, since we’re in the year 2012? Trust me on one thing in anyway – IF the world is gonna go under, its going without me!

    • A couple of years ago, while rummaging around in the available on-line documentation, I ran across a study that was trying to evaluate really old earthquakes and the historical record. One of the things that the researchers did, was to look for the skew in the number of quakes detected and to correct for it.

      This is an example of something that I call “techno-skew”.

      The simple fact is that more and more seismic gear is installed as time goes by. As the quality and performance of the new gear gets better, it slowly phases out the older equipment, much of which stays in operation until it finally gives up the ghost.

      Over all, if you look at it on a long time scale, you should be able to see a measurable increase in the weaker events as the over all sensitivity of the various networks (as a whole) get better.

      It would look something like this.

      This is a plot of the number of events at each half magnitude increment over time. These are raw counts that accumulate over time starting around 1973.

      This data is from the USGS listings at http://earthquake.usgs.gov/earthquakes/eqarchives/epic/

      Note how the growth rate in the number of lower magnitude events rises over time, as compared to the next magnitude level.

      • Thanks Lurking.
        This illustrates what I have been saying to people for ages .
        Not only are smaller tremors now detected but more information is available to more people. hence it appears that earthquakes are becoming more frequent.
        There again I could be wrong it could be the precursor of the apocalypse I am NOT an expert. 😀

  12. ONE more thing, my freaking building was just shaking as h***, thought it was the industrial area beside here, but looks kinda dark there. I can suspect an earthquake, but in Norway? And hey, I’ve never felt an earthquake ever in my life, so what I wonder now is if there is anywhere I can figure out if there was or not? It lasted for about 10-20 seconds…

    • Hello Christina!

      I do not know which part of Norway you live in, so this answer will be rather general for Norway.
      Your mountains where produced by an eruptive process at the MAR. They slammed into the older mountains that exists in the eastern part of Norway and Sweden many million of years ago, and got even higher.
      So, Norway has quite a few residual quakes of that process, they range up into 4s even though those are rather rare. But on a daily basis there are earthquakes in Norway, and those that are two or more would be felt.
      So I do not doubt in any way that it was an earthquake that you felt. From the time you felt it I would guess something like a 3M at distance.
      There is also isostatic rebound earthquakes as the heightening of the land is still going on in Norway. In Sweden we have found traces of what is judged to have been the largest earthquake ever. The Stora Sjöfallet 11M quake. Yes, it actually split Sweden into two parts for a time. But rest assured, there is not that much energy generated any longer since the uplift is so much smaller today, then it was back then. Isostatic rebound nowadays creates 3s at most.

      If you live higher up in Norway it could have been the 4M mining blast at the Aitik mine that you felt. Those are filtered out from the EMSC and USGS quakelists since they are known beforehand, and also have different signatures. Also makes the US nuke test search programs go nuts, but is used to calibrate the systems for small kilotonage undrground tests.

      EMSC updates continously, when a quake get into the list varies a bit depending from which system the data comes from, but normally a quake appears withing 15 minutes or less. Icelandic quakes are actualy first seen there, before showing up on the official IMO page.

      Oh, regarding the Stora Sjöfallet Quake, it did not only crack Sweden and Norway in half, it also opened the gates for the Littorina Sea creating a massive flood which emptied the sea (5 times larger than the Baltic Sea) within days.
      If that had happened today it would have been counted as the largest natural disaster ever… It is believed that it whacked up to 90 percent of the then nomadic inhabitants in Sweden and Norway, and that 50 percent where whacked in the other areas due to tsunamis.
      And no Daily Mail, it wont happen again.

      • I’m been trying to track down any mention of this quake, not having much luck. Have you got a link for some further reading ?

      • Probbly that lovely tremor frequency you found that seems to exist in all active volcanoes that I have found data for. It warries a small bit over time, and an equally small bit between volcanoes, but it seems to be there always. It is also visible during run-ups to the actual eruptions.

  13. ER Comment

    A ship from the Spanish Armada (Army) has been cruising along the coast of La Restinga this afternoon and tonight. Julio del Castillo Vivero did timelapsed his movement and it was not clear what he exactly was doing. We know that the Spanish Armada ships will take part in the bathymetry sessions, but they are only scheduled at the end of March. Following Julio’s reports he was making 8 circles in 1 hour ?!? So, for now, it will remain a little mystery why the ship is there.

  14. Recent comments on Avcan FB

    buenos dias, el tremor sigue aumentando y la sisimicidad digamos que es constante.

    good morning, the tremor continues to increase and the sisimicidad say that it is constant. (Translated by Bing)

    42 minutes ago · Like.

    Xavier Cabello podria ser que la lava,gases ect. siguiera un camino subiendo 12km.

    could it be that the lava, gases ect. follow a path climbing 12 km. (Translated by Bing)

    39 minutes ago · Like.

    Xavier Cabello perdon se me colo el enter. my pregunta es si la lava puede subir a un dique a 9km. y luego bajar por los conductos a15km. y volver a salir por la zona de erupcion.

    sorry is me colo enter. My question is if lava can upload to a dike to 9 km. and then walk down the a15km duct. and back out by the eruption zone. (Translated by Bing)

    • Na, that line does not show anythiing really. It was either a small quake, or as it says, a large truck running past.

      • Actually, what is shown is Hugh Grant running past in the background in his truck. Took me a while to get it, and also to actually read the text… 🙂

        • Perhaps machines dont show it.
          Neither our 5th senses…
          But my feeling and 6th sense tell me the bug is growing yet…
          We should see if this 6th sense is based on some datas hiden in our common sense or it is based on nothing… hahaha
          I bet for the 1st option… hahaha

    • It seems that the page is not updating that often. Parts of the data is from 2011, and the quakes get reported with a 4 day lag.

  15. For some Sci-Fi fun with Arthur’s Seat read Moonseed by Stephen Baxter.
    The end of the world starts there!

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