Recently Nathan took you on a comfortable journey into the Eifel volcanic field. But what is the origin of this intraplate volcanism and where will the journey go?
About 400 million years ago during the Devonian, the Age of Fish, when only plants and insects roamed the land, Laurussia and Gondwana converged into the supercontinent of Pangaea forming the European Variscan Belt. It includes vast mountain ranges stretching from Portugal to Turkey. The Rhenish Massif in central Europe is one of the outcrops of this period, others are the Massif Central in France or the Bohemian Massif in Czech Republic and Poland.
The Rhenish Massif is mainly made of highly folded sedimentary metamorphic rocks, mostly slates, hence the name “Rheinisches Schiefergebirge” or “Rhenish Slate Range”.
Geological map of the Rhenish Massif. Author Jo Weber (Wikimedia Commons)
When the Age of the Mammals dawned and Africa started to collide with Eurasia, a whole lot of volcanic activity started north of the rising Alps. This belt was termed European Cenozoic Volcanic Province by Meyer and Foulger. In the Alpine forelands extensional rift systems developed with the Rhine graben as a prominent feature. Volcanic activity of that period can be found in France (Massif Central), Germany (High Eifel, Westerwald, Vogelsberg, Rhön), The Czech Republic (Eger graben) and Poland (Lower Silesia).
The ductile and tough shale and slate bedrock of the Rhenish Massif presumably was incompatible with extensional rifting. Instead the region acted as a hinge between shear rifting along the Upper Rhine Graben and extensional rifting at the Lower Rhine Basin (Illies et al. 1981).
The Eifel volcanic field is situated west of the Rhine river near Koblenz in the center of the Rhenish Massif. Fluvial deposits prove that this area was uplifted up to 300 m since the Pliocene epoch 5 million years ago and that the uplift had accelerated during the last 800,000 years with maximal elevation around the Eifel volcanic field. Since then the Rhine river and its tributaries were forced to cut deep valleys through the Rhenish Massif, flowing past Hunsrück and Taunus, Eifel and Westerwald, Ardennes and Süder Uplands.
The most recent volcanic activity in the West and East Eifel volcanic fields coincides with this uplift which amounts to 0.35 mm per year on average. The dome building may be a combination of widespread uplift of the so-called Rhenish Shield due to horizontal deformation from Alpine orogeny (Illies et al., 1979 and 1981; Meyer and Stets, 2002) and more locally by uplift due to the Eifel mantle plume (Schmincke, 2007).
To study the deep structures of the Eifel region the Eifel Plume project temporarily deployed a large network of seismic stations in 1997. A shear wave velocity model suggested a 100 km wide low-velocity structure extending down at least 400 km into the upper mantle which could indicate an area of increased temperature and partial melting. It remains debated whether this anomaly caused the Eifel volcanism. Other volcanic areas of the European Cenozoic Volcanic Province lack clear evidence of deep mantle plumes and the spacial distribution and timing of eruptive phases is not consistent with movement of the European plate over a fixed hot spot.
Alternative models could be a magma source derived from previous Alpine subduction or local decompression melting from passive rifting caused by tectonic deformation of the crust. Notably, the Mohorovičić discontinuity (Moho) is only 30 km deep below the Eifel while under the Alps it goes down to about 50 km which could give rise to some mantle turbulence and convection.
South-North section of the Moho beneath Europe between 6 and 9° longitude. Depth is highly exaggerated (Image by chryphia). Data from www.seismo.helsinki.fi/mohomap/
There is an overwhelming amount of literature about the recent quaternary activity of the 300+ volcanoes in the Eifel, sadly most of it paywalled or even without online access, because published in books or exotic German journals. So the following is taken from secondary literature. The eruptive history was e.g. summarized by Schmincke in Mantle Plumes (2007), Schmitt et al. (2010) (see Fig. 1 here for a map of geological map of the East Eifel volcanic field) and is nicely illustrated in this German blog post.
In summary, there seem to have been at least four main eruptive phases:
700,000 to 450,000 years before present: the main bulk of monogenetic volcanoes, small cinder cones and short lava flows erupted in the West Eifel and late some in the East Eifel. Their lava contained leucite (potassium rich) basalts, poor in SiO2, indicating an upper mantle source.
The West Eifel then fell dormant for several hundred thousand years.
430,000 to 360,000 years before present: In the East Eifel the Rieden complex (“Riedener Kessel”) west of the Laacher See had its most productive episode sputtering out several cubic km of lava in larger cinder cones and kilometer long phonolithic lava flows out of a 4 km diameter caldera system.
215,000 to 190,000 years before present: In the East Eifel the Wehr volcano (“Wehrer Kessel”, a 2 km diameter depression) west of the Laacher See and many large scoria cones in the Neuwieder tectonic basin erupted several cubic km of dense rock equivalent. The lava was highly differentiated phonolitic and rich in SiO2, indicating that country rock had been partially melted. During this time the first Maars were blasted out of the West Eifel volcanic field.
100,000 to 10,000 years before present: the West Eifel field was peppered with Maars still erupting the original lava, the last one to be the Ulmener Maar. Simultaneously, a new kind of lava, basanites, poor in potassium, hence leucite free, presumably from the asthenosphere, created large cinder cones and lava flows sometimes right next to the Maars (e.g. Meerfelder Maar next to the Mosenberg).
In the East Eifel only the Laacher See erupted 12,900 years ago, without doubt the most powerful eruption of all time in the Eifel probably equalling the total output of the West Eifel volcanic field. The Laacher See erupted more than 6 cubic km of magma within days, with an at least 25 km high eruptive column spreading tephra from Italy to Sweden. The magma is thought to have differentiated over several thousand, possibly tens of thousands of years, showing zonation from mafic to evolved phonolite and carbonatite. Pyroclastic flows temporarily built a dam in the Rhine river which eventually broke unleashing torrential floods, illustrated here (in German). Finally the emptied magma chamber collapsed leaving this recreational lake.
The “Loch Lochy” of Germany, the Laacher See. Image by USEBlackbird (Wikimedia Commons)
So the Eifel volcanism occurred in tens to hundred thousand years periods intermitted by hundred thousand years of dormancy. There was a general trend of eruptions starting in the NW progressing to the SE. Eruptions became increasingly voluminous and explosive with time and there was a shift of lava from an upper mantle source to partially melted crust.
Today the Eifel volcanism is dormant. As already featured in Nathan´s post abundant CO2 emission is a sign that the Eifel volcanic field is not extinct. But also seismically the region is active. Earthquakes during the past 36 years are almost exclusively confined to the upper 15 km. There is no indication of magmatic origin so far. The highest earthquake density is east of the Laacher See and west of the Neuwieder basin along the Ochtendunger fault zone on a NW to SE axis, aligned to the general tectonic setting in the Rhenish Massif.
Recent earthquakes (Sep 2012 to Jan 2013, green, enlarged) and earthquakes dating back 36 years recorded by the seismic station Bensberg, University of Cologne. Image by chryphia.
And here a 3D plot:
Since 1975 up until January 2013 over 1180 local earthquakes were reported by the seismic station Bensberg (University of Cologne) with some increased frequency in the last years.
Earthquake data from the seismic station Bensberg from 1975 to 2013 (between 5.21 and 5.472° lat and 7.25 and 7.65° lon, as in 3D plot). Image by chryphia
Helium and other noble gases that are found in high concentrations around the Laacher See are indicators of the volcanic origin of the Mofettas. Helium isotope 4 (4He) is naturally formed in earth´s crust. Another rare Helium isotope, Helium 3 (3He), is produced by fission and bombardement with high-energy cosmic rays, so what we find on earth was created before our solar system formed. In the atmosphere it escapes into space. Looking at the 3He to 4He ratio in volcanic gases relative to the ratio in earth´s atmosphere (Ra) gives a clue about the source of the magma. If it´s of deep origin, it still should contain relatively high 3He. The 3He/4He ratio measured from Mofettas from the Laacher See is 5.5 Ra, indicating an upper mantle source, but it is less than measured at mid oceanic ridges (8 Ra), thus there is mixing with 4He from the crust.
So there we are today. Was this the end of it for the next 100,000 years? As long as the Brubbel squirts and the earth rumbles occasionally we can´t be sure of it. Maybe the ants will tell us one day.
In logic, an assumption is a proposition that is taken for granted, as if it were true based upon presupposition without preponderance of the facts. (Wikipedia)
Back around May of this year, Carl asked me to do a series of simulations using KWare’s Heat3D, a program written by Ken Woheltz and the Reagents of the University of California under the sponsorship of the US Governement. It’s a cool little program that allows you to run heat simulations of magma intrusions into rock of varying characteristics. I had been prompted to write an article about one of the more perplexing areas in Iceland (well, to me it is). Not feeling that I was up to the task, I offered to do the supporting graphics if Carl could find someone to write the meat and potatoes of the article. I killed off a weekend working up the plots, but two of the catch points that we ran into were; “What temperature of the intruding magma should we use?” and “What exactly is the geothermal gradient of the region?”
With those two uncertainties, and the bedlam of real life, the post never made it to the forum. Things happen.
Before I go on, I must warn each and every reader here that I am not a seismologist, geologist, or bona-fide expert in the field. I read a lot, have been “studying” geology and physics in some shape form or fashion for about 37 years. I am just an amateur like many of you, so there is ample room for error.
With that out of the way… now we discuss
First, “The Dead Zone” is not an actual named place. It’s just a colloquialism specific to VolcanoCafe. It’s that region of Iceland between Katla/Torfajökull and Bárðarbunga/Grímsvötn. I refer to it as “The Dead Zone” due to the seeming low number of quakes. Historically, and pre-historically, the region is quite active with fissure eruptions. Irpsit and others can give you more definitive dates and names about the area, but I am limited to what I can cobble together from various sources. There are many other features here, but the main ones that I can find data on are Veidivötn, Vatnaoldur, Skaftar, Eldgja and Trollagigar. (spelling as listed in GVP and may be missing some of the diacritical marks) Veidivötn, Vatnaoldur, and Trollagigar are part of the Bárðarbunga system, Eldgja belongs to Katla, and Skaftar belongs to Grímsvötn. (As parts of the parent volcanoes fissure swarms). As you can see from the overview plot, there just are not very many quakes in this region. (Ignore the dot dashed blue line, that was part of the original plot set and is not used here)
Now, why is the Dead Zone dead? Because it is really… really hot. Much more than you would think. When an eruption is completed, magma sits and cools after the eruption is over with. This cooling rate depends on the thermal conductivity of the surrounding rock. For Basalt, the heat capacity is 840 J/kg K. (this is what I used in the simulations), Granite, for comparison is 790 J/kg K. This is in part due to its lower density. How it works… in order to raise the temperature of one kilogram of the material by one Kelvin (same as one degree C), you need 840 Joules of energy (for Basalt). Since we are talking about heat capacity, Water is 4185.5 J/kg K and Ice (at 0°C) is 2090 J/kg , so you can see how water or ice can drastically affect what is going on. This is one of those “gotchas” that can throw this whole scenario off. This area has a high water table and that can seriously affect how accurate the simulations are. Keep that in mind as I continue.
Anyway… when a dike intrudes into rock, whether it erupts or not, it starts loosing heat at a rate that can be calculated (provided you have the skill, or a program written by someone with the skill). Heat3D runs through the iterations of how heat migrates into the surrounding rock.
Here is how a single intrusion works out over a few years.
In my original set of graphics, I used a temperature of 1600°C magma due to the runniness of the flows and how far they traveled. My original guess was 1100°C based on a statement that I had seen in a paper, and much discussion occurred between Carl and myself about what would be the sane value to use.
“Time constraints on the origin of large volume basalts derived from O-isotope and trace element mineral zoning and U-series disequilibria in the Laki and Grímsvötn volcanic system” Binderman et al (2006) places the temp in the 1120–1140 °C range based on a “Mg in glass” geothermometer. (calculating diffusion and formation rates vs temp and pressure). Another reference (that I can’t locate at this moment) implies a temperature of 1200°C at 250MPa for one of the clast minerals. 250 MPa is in the 10 km depth range. Still uncertain of what temp to use, I went with the program default of 1250°C.
I used a 10 meter dike width based off of the average of three known dike sizes contained in “Geodetic GPS measurements in south Iceland: Strain accumulation and partitioning in a propagating ridge system” LaFemina et al (2005). This produces a really crappy 95% confidence range of 0.5 to 10.2 meters. (three samples is horrendous, but it’s all I had) Since the size of the plot grid has a direct play in how long the simulations take to run, I used 10 meters in order to get the simulations done in one evening.
Okay… now the actual run. As noted, this is not the original, and for brevity, I focused on only one system, Veidivötn. In case you didn’t know it, Veidivötn is probably the most lively fissure system in the region. It’s responsible for many of the Tungnaárhraun tephra layers. (THc. THd, THe…) GVP places an event there at the following dates: -6650, -4800, -4600, -4550, -4400, -4200, -1200, 150. For each eruption, I placed a 10 meter wide dike and ran the program out until the next intrusion date, which was then added and the process repeated. Another “gotcha” that you should be aware of, the eruptions did not necessarily occur in the same part of the fissure. This simulation assumes that they did. In effect, this skews the region towards being hotter than it might really be (and don’t forget the possible effect of the water that I mentioned previously)
So… here is the final product for what conditions may be like under the Veidivötn fissure. The temperature scale from the previous plot applies here.
Pretty gnarly eh? This is the crux of why I think that you won’t really see many small quakes in this region. Each one of those fissure lines has a heat structure similar to this. The crust is for the most part, plastic and yields to any stress that comes along… until it arrives too quickly for it to give. Then you have the larger quakes and potentially an opening of the fissure if the conditions are right… such as a nearby parent volcano being at or near erupting and having a ready supply of magma to flow down the rift and open it the rest of the way up. Structurally, there isn’t really much there to hold the two sides together. Plate shifts can do it (tectonic), or a parent volcano.
From “IAVCEI General Assembly 2008 Conference Field Excursions, Excursion 1: Historical Flood Lava Eruptions The 1783-84 Laki and 934-40 Eldgjá events” August 14-17 2008
“In 1783 the people of south Iceland had enjoyed a favourable spring and were looking forward to summer. However, their destiny was about to change. Weak earthquakes in the Skaftártunga district in mid-May were the first sign of what was to come. The intensity of these earthquakes increased steadily and on 1 June they were strong enough to be felt across the region from Mýrdalur and Öræfi. The earthquake activity escalated up until 8 June when a dark volcanic cloud spread over the district, blanketing the ground with ash (Figure 18a). The Great Laki eruption had begun.”
I’ve worked out the distances to Mýrdalur and Öræfi from the Laki site and applied an Mw to MMI estimate based on a few real world quakes from the USGS catalog in order to get a feel for how the power drops off over distance. Based on the MMI levels at which a quake becomes detectable by an unaided person, the quakes leading into the Laki event were in the Mag 4.5 to 5.0 range.
It’s a bit of a reach, but extending the formulas from “New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement” Wells and Coppersmith (1994) down to Mag 4.5, you get the following numbers.
Mag 4.5 – Surface rupture length 0.5 km, Subsurface rupture length – 1.3 km, Downdip rupture width – 1.7km.
Mag 5.0 – Surface rupture length 1.3 km, Subsurface rupture length – 2.7 km, Downdip rupture width – 2.9 km.
THESE ARE ESTIMATES
There is a bit of slop in the formulas, it is an attempt to get a working estimate of the physical manifestations that you would see from a quake. These particular formulas are only considered reliable for events down to Mag 5.2, but they do track well with no oddities in the curves. Below 5.2 the confidence in what the formula says drops off.
From that, it seems that the Mag 4.5 to 5.0 quakes are what is needed to open the system up. They have the right sort of features; the crust itself has likely healed very little from the previous events and should not take a lot of energy to re-open.
All this rumination and reading is one thing… but there is always something missing when you think and talk about these fissure eruptions. That’s the scale of the things. Since none of us were around, we just don’t know or have a frame of reference. All we have are eyewitness accounts. From some of those accounts, we know how long or how tall the fire curtain was, but that’s it. Just numbers in a book. Here, I have scaled an image of a generic fissure eruption and placed a few well known silhouettes in front of it so that you can see just how big these things are.
Enjoy.
GEOLURKING
GL Edit: The silhouetted buildings are;
Empire State Building – 443.2 m, Taipei 101 – 449.2 m, Burj Khalifa – 829.84 m, Sears Tower – 527 m, Petronas Towers – 451.9 m
From what I know Laki eruption could be observed from almost anywhere in Iceland, in distance. The reports even speak that you could see the fountains from far away, but probably not everywhere in Iceland, as 1km high is not enough for that.
This put me on a search for two of the images that I made for the original article. I was able to pull them from Google archive of my mail.
They are not as stunning as the scaled image, but they are worth pondering. The ruddy maroon rectangle represents the Skaftar (Laki) fire curtain anchored to the surface, as seen from a couple of locations.
Photograph by Jeff Shea. A range of north Greenland shield volcanoes eroded by glacier ice so that they more remind of a range of strato-volcanoes.
Earlier today commenter Lucas Wilson asked me about volcanism in Greenland. So, I thought I should write a short piece on what once used to drive the volcanism there.
But let us start with what we today call the Icelandic hotspot. In here we have a tendency to talk about large volcanoes now and then, and sometimes about what is called “super volcanoes” in the media. But, the fact is that Iceland is both the largest volcanic structure on the planet, and also by far the oldest active one.
Let us start with largest. Iceland stands for between one third and half of all the magma on the planet during the last 250 million years. The rate of lava produced is fairly prodigious. Also, few know how long this has been going on. The answer is that it all started far before Iceland was born. Time for a history lesson.
Iceland was born as the Icelandic Hotspot moved close to the Mid Atlantic Rift; Iceland was born from the mid parts to the west and the east. This is as a function of the hotspot giving extra magma to the normal volcanism of the MAR, and thusly building the volcanic edifice known as Iceland as the MAR rifts apart.
Photograph by Ansgar Walk. Trap formation eroded by Glaciers, Ice age glaciation, and coastal erotion. Baffin Island.
Okay, now to the age thing. The Icelandic Hotspot is one of the really few surface expressions on the planet that is stationary. I know, the hotspot per see is not visible, but its effects are. So, as the continents and plates have fun surfing around bumping in to each other they slide over the poor hotspot.
A few tens of millions of years ago it was a part of the North American plate that slid over the Hotspot, and as that broke apart magma pushed through and created Greenland. As the now archipelago of Greenland slid away it lost its capacity to have eruptions pretty permanently.
Before that it was Newfoundland that popped up as it slid over the hotspot. And before that we had the same hotspot creating the largest Large Igneous Province on the planet, the North Arctic Igneous Province (NAIP). Before that Labrador and Baffin Island slid over the NAIP, and that put us at about 95 million years ago. And 130 million years ago it created the Alpha Ridge. Any super volcano will have an inferiority complex to that eruption.
Before that and even further down in time it was known as the Siberian Traps, the largest on land eruption. And now we are back 250 million years in time. Before that things get a bit harder to track.
Photograph by Jxandreani, wikimedia commons. This is a part of the Putorana-Norilsk Deposit.
Here comes an interesting thing. What is today known as the Icelandic Hotspot has been conveying about the same amount of magma since the Siberian Traps. Give or take the eruptive rate has constantly been around 0,5 to 1,5 cubic kilometer per year since day one. And as we all know the average erupted material is only 1 in 20 of the magma that comes up. The rest stays as intrusions or inside magma chambers. So, on an average year the Icelandic Hotspot will loft up 20 cubic kilometers of material.
Now some of you will say something like “Hey dude, it never erupted continuously, so it can not be the same. And dude, the Siberian Traps erupted more material than Iceland”.
The reason for it not having erupted constantly is that it need either pressure enough to crack a continental plate, or the magma had to wait for a spot that was weakened that it could crack. The Siberian Trap was a momentous episode, but the largest separate eruption was “only” 3000 cubic kilometers of lava erupted (Norilsk Deposit). In the end the Siberian Traps is only standing for a slight elevation in erupted material even though a lot of magma had accumulated under the Eurasian plate before onset of eruption. Average erupted material during the Siberian Traps was only twice what Iceland is popping out on average.
The Siberian traps carved by a river into a kilometer high cliff.
We should also remember that eruptions happen in cycles. The Norilsk Deposit is probably a hundred million year event, or in other word, it would take on average 100 000 000 years in between every eruption of that size. It is estimated that it took about a hundred years to erupt that amount. So, on average 30 cubic kilometers per eruption year and that is not a nice thing to be around, but far from what it takes to produce a mass extinction.
We know that there are about 2 to 4 eruptions on the scale of above 10 cubic kilometers in Iceland today per every thousand years. They tend to happen on a 270 year cycle. We also know that every few thousand years we get them in the 30 to 50 cubic kilometers. Most likely those come in about 1000 year cycles, but in various places over Iceland, and on average over time.
About once every 10 000 years we get one upwards to a 100 cubic kilometers. I do not know of any eruption in Iceland significantly larger than that, and would be surprised if anyone finding one. The reason of course is that the MAR creates a fairly open passageway for the magma. Norilsk was happening due to the dense rock of the Eurasian plate storing up magma under it until it cracked, so the necessary magmatic pressure can most likely not build like that in Iceland.
So, now we know that old huge volcanoes cannot erupt again due to the magma-hose being disconnected as the plates slide away from the “gas-station”, and we also know how persistant the hotspot is.
Super volcanoes, well all is relative…
Bonus Riddle from Alan
Many of you might have missed that we tend to have volcanic and geologic riddles every friday in here. Lately we did not have that due to El Hierro taking center stage. But we do know that there are many that love them, so here is bonus riddle. Remember, it should end up in something rocky.
Huh! Last week, I went into a nice bakers – they only had this rock-cake!
Over my lifespan, I have looked at seven eruptions in progress, small and large, both from land or from airplanes. The first I witnessed was the Surtseyan one (1963-1967), looking at it from the mainland via binoculars it looked beautiful, the plume rising high from the sea, ash mostly fell into the sea, and visble at night were the lightnings, plenty of them on some nights. This was not dangerous eruption as it was far out in the ocean. Hekla in 1970 also posed no real threat to the population, it was mostly lava running on desolate ground and in the high mountains. Ash fell on farmland, this affected sheep and other livestock, mainly Fluor chemical poisioning accumulating in the grass and in ground-water. Gases were about near the volcano. All Hekla eruptions produce gases. Some volcanoes more than others.
Keep livestock indoors if possible. The next one was potentially dangerous, for the people living in Heimaey Island, 23 January 1973, waking up in the middle of the winter night with the eruption just on the edge of town, a bare hundred meters from the nearest farmhouse. It was not predicted and took nearly all by surprise. But the Police, the Almannavarnir Agency (now under State Police Commissioner) and the local rescue teams moved every un-needed person away on the very first night. Only needed ones and reporters stayed behind. They also arranged for domestic aircraft and military helicopters flying an “air-bridge” but mostly used the fishing-boat fleet, as it was in Vestmanneyjar-Heimaey harbour due storm the previous night, then sailing in rough seas to the mainland. In next few days a passenger liner and cargo ships were also sent to the island, a ship was used as base for rescue persons and the cargo ship moved out cars, furniture, or just about all machinery they deemed wirth to be moved. A few US Navy cargo planes helped later with furniture moving but USAF helicopters helped
move stretcher patients from the hospital already in the first night. Some days later an live TV broadcast was started. Everything worked, but it took several years for the people to move back and have everthing normal as before. I took a few photos on my first visit there (in 1974), then almost everything was still covered with black ash and pumice. And the lava was still warm.
Copyright by Eggert Nordahl. Heimay 1974.
Living in the city, Reykjavík, this affected me too. My father woke me up that morning but I did not have to go to school – it was used as registration center for the people moved out from Heimaey – mostly by boat (and then buses to the capital). This situation lasted some days.
Eventually all got new places to stay and school was open again. Since then I have watched many volcanic eruptions, including Fimmvörðuháls and Eyjafjallajökull in year 2010, and not to forget last years Grímsvötn. I went part way there to have a closer look but staying in safe area and returned early as ash was heading my way. Near the edge of the ashfall one could feel the ash in ones eyes and in ones teeth. I always have a bag with some spare clothes on my travels, and a mask (like the one you see doctors use in hospitals but also worn by workmen breaking rock with air-hammers). They wear a mask! I drove away before having to put it on. Also I never needlessly go under an ash plume, there is risk of lightning strikes, besides ash can damage auto engines and everything mechanical. Going about in areas of ashfall, one must use a mask and goggles, and have clean water ready to clean ash, if it gets into ones eyes.
Wow, this is big lists, but very carefully compiled. These are my countrys official website.
Below is my personal writings. It may be regarded secondary and rather personal. My first “number one” is GAS. It can be odorless, tasteless and lethal. Simply stay away if possible. If not able to go, do not stay in the cellar or on ground floor. Have windows open and let air blow about the house. Have fans turned on to refresh air, preferably from the outside. Stay and sleep as high as possible, avoid going needlessly into low areas, depressions in the landscape or earthquake-cracks. Do not go into old tunnels or caves. Do not travel alone, and let others know of your travel plans.
EARTHQUAKES – I have experianced a number of them, and these can be dangerous, especially in old brick or stone buildings, but safest are considered houses made from wood or properly steel-reeinforced concrete. Then the rule is have doors to internal rooms open (i.e. not locked) then they are less likley to jam (closed) and it is advised on hold an exercise how and where to exit the house or apartment if it becomes unsafe. But first, stay, do not run.
If quake hits (5,0 M) then stay in a corner, under a strong table, or stay put in a doorway.
Always watch for falling objects. Avoid having things fall onto you in your bed. Check if everybody is allright in your house afterwards. Volcanic Earthquake risks are rather low, tetonic quakes are the ones that can be dangerous.
Copyright by Eggert Nordahl. Heimay 1974.
VOLCANIC ERUPTIONS – Generally people should not live on volcanoes. But most islands are old volcanoes. If faced with an onset of eruption, best is to leave and stay some place else. If that is not possible, be prepared. There are many ways to prepare. Think first. Perhaps make a list of what one needs doing and when to do it. Where will I go, when and how. Is it safe staying. Think of dangers on staying put. These questions I can not answer here. Please, Consult Your Local Emergency Plans (on internet) or find out before anything happens.
If unable to go to a safe location beforehand, please use my text as rough guide only.
It is not perfect and I am not expert on this matters. My experience is listening to the State Radio broadcasts relative to several emergencies and how others react to the emergency. My training and experiance is several first-aid and fire-fighting courses and then flight search for lost airplanes, and carrying and caring for several severely wounded from several accident locations.
Preparing can be done in many ways. One is to have bag at ready with a few spare clothes, passport, money/credit card, water, medicine, small medical kit to mend cuts and bruises, hand-held (battery powered) radio, flashlight and batteries, have mobile phone charged beforehand and bring along the charger, have good shoes or boots, also warm-hat, pair of good gloves, a raincoat, blanket or sleeping-bag for everyone, an umbrella etc. Do not overload car with heavy furniture or other unneeded stuff. That can wait. Perhaps take along some personal papers or other light stuff, like small cosmetic kits or electric razor. Basically only things for travel and have perhaps limit on one bag for each. Have pets is their usual (portable) travel cages and bring along food and water for them, and also have small amount of “instant food” for the travel. Here I am referring to food that does not need cooking. Think choclate bars, fruit etc. Sandwitches or light snacks can me made before leaving. Have photos and complete list of all family members (including pets) in case family gets split up (this can be saved on smartphone). Leave a written note behind on travel plans. Exit your house in safe mode (generally leave one light on by front door and freezer/cooler in normal working order, or turn it off if empty). Turn all other appliances off, including TV (by removing socket from wall connection, reducing risk of lightning strikes). Leave heating on in case of frost can damage waterpipes. Have vindows closed and shutters secure. If moving away by car, have car checked at beforehand for it having enough fuel, water and oil on engine. Carry car keys in pocket at all times. Some of abowe mentioned items can be stored in the car trunk beforehand, and car can be used as shelter, if house becomes damaged or unsafe. Do not run, go (drive) away slowly and give lift to/help others if seats allow. One tip I use if using car as shelter is let engine run at idle for about 15 min (for heating and battery charging) then switching off for 30 min (depending on outside temperature). This way save a lot of precious gasoline.
Here in Iceland we know we can trust the Almannavarnir and the Icelandic Radio (RUV) for warning data, they are notified by direct calls from the IMO, the Police or the University Earth Scientists. The IMO volcanic earthquake data (including warnings) is online and can be viewed at all times. It is very effective system and used on regular bases. It is normal part of life here. If anthing happens, the resuce teams are on watch 24/7, all days of the year, in all areas. And they have the equipment they need, including 4×4 jeeps, snowmobiles, ambulances, rescue helicopters and rescue and coastal patrol boats. There are emergency plans already in stock regarding Katla and have been used on Eyjafjallajökull eruption. We also have risks of storms, blizzards, avalances, lightnings, floods, earthquakes, eruptions, fires, chemical accidents, large airliner crashes etc. Here there always are pre-planned assembly points for the rescue services and affected people – generally in schools or similar buildings – and the rescue services and Almannavarnir make announchements on the RUV FM “Radio 2” (Rás 2) and what to do in each case. They have all the info and instructions (we do not have all). We trust them. Generally wait for instructions on the radio, this may give vital clues to what is going on. Do not use mobilephone or make any unneeded calls.
Save on power if possible. Stay in safe area is the best.
ISLANDER
Copyright by Eggert Nordahl. Heimay 1974.
Como los islandeses se preparan para una erupción – Un testimonio personal
Durante mi vida, fui testigo de siete erupciones en curso, grandes y
pequeñas, tanto desde tierra como desde aviones. La primera que vi fue la de Surtsey (1963-1967) – mirando desde la parte continental a través de binoculares, se veía hermosa – la pluma elevándose desde el mar, una profusión de cenizas que en su mayoría cayó en el mar y en la noche, los relámpagos, un montón de ellos en algunas noches. Esta erupción no fue peligrosa, ya que estaba muy lejos en el océano. Hekla en 1970 tampoco ha representado ninguna amenaza real para la población: era sobre todo la lava a correr en un terreno desolado y en
las altas montañas. La ceniza cubrió la tierra, afectando a los
rebaños de ovejas y otros animales, principalmente debido a la
intoxicación química por el flúor que se había acumulado en el césped y en las aguas subterráneas. Los gases se concentraron cerca del volcán. Todas las erupciones del Hekla producen gases. Algunos volcanes, más que otros. Si es posible, usted debe mantener el ganado muy bien protegido.
La próxima erupción fue potencialmente peligrosa, porque los
habitantes de Heimaey, el 23 de enero de 1973, fueron despertados en medio de aquella noche de invierno con la erupción justo en el borde de la ciudad, a unos cientos de metros de la granja más cercana. La erupción no se esperaba y se llevó casi todo el mundo por sorpresa. Pero la policía, la Agencia Almannavarnir (ahora bajo la jurisdicción de la Policía del Estado) y los equipos locales de rescate hicieran el traslado del sitio, ya en la primera noche, a todos aquellos no aptos a ofrecer ningún tipo de ayuda. Sólo aquellos considerados útiles y los periodistas se quedaran allí. Para el transporte fueran ordenados aviones civiles y helicópteros militares que volaban en una especie de “puente aéreo”, pero la más utilizada fue la flota de barcos de pesca anclados en el puerto de Heimaey-Vestmanneyjar a causa de una tormenta que pasó la noche anterior, que entonces navegaran por los mares agitados hacia el continente. En los días que se siguieron, un barco de pasajeros y buques de carga también fueron enviados a la isla; el
barco fue utilizado como base para el personal de rescate y los buques de carga transportaban autos, muebles, maquinaria, sólo lo considerado esencial para el transporte. Más tarde, algunos aviones de carga de la Marina de los EE.UU. ayudaran en el transporte de muebles, mientras que helicópteros de la Fuerza Aérea ayudaran en el traslado de los pacientes hospitalizados en camillas, en la primera noche. Unos días más tarde, comenzó la transmisión de TV en vivo. Todo funcionaba bien, pero le tomó varios años para que la gente regresar a la isla y su vida volver a la normalidad. Tomé algunas fotos de mi primer visita al sitio (en 1974), cuando casi todo aún estaba cubierto de ceniza negra
y piedra pómez. Y la lava todavía estaba caliente.
Viviendo yo en la capital, Reykjavik, el evento me ha afectado
demasiado. Mi padre me ha despertado en aquella mañana, pero no tuve que ir a la escuela – esa fue utilizada como centro de información para las personas que emigraron de Heimaey – en su mayoría en barco (y luego en bus a la capital). Esto duró unos pocos días. Finalmente todos fueron recibidos en nuevos lugares y la escuela fue de nuevo abierta.
Desde entonces, fui testigo de muchas erupciones, incluyendo
Fimmvorduhals y Eyjafjallajökull , en 2010, por no mencionar la del Grímsvötn del año pasado. Fue hasta la mitad de la carretera para verla más de cerca, me quedando en un lugar más seguro, pero tuve que regresar antes del tiempo debido a la ceniza que venía hacia mí. Cerca del borde de la nube de cenizas podía sentir la arena en mis ojos y dientes. Siempre llevo una bolsa con unos cuantos cambios de ropa en mis viajes, y una máscara (como las que usan los médicos en los hospitales, o los trabajadores que operan con martillos neumáticos).
Llevan la máscara! Ya me había alejado con el coche cuando fui a
ponerla. Además, nunca me paso dentro de una nube de cenizas sin
necesidad: hay riesgo de rayos, y además el hecho de que las cenizas pueden dañar los motores de los coches y todo lo que es mecánico. En el tránsito en las zonas de caída de ceniza, se debe utilizar una máscara y gafas, y siempre hay que tener disponible agua limpia para lavar las cenizas de los ojos.
Ufa, esto es una gran lista, pero compilada con mucho cuidado. Este esel sitio oficial de mi país. A continuación se presentan mis escritos personales. Se puede considerarlos como secundarios y algo personales.
Mi “número uno”, el primero de todos, es el gas. Suele ser inodoro, insípido y mortal. Basta mantenerse a distancia, si posible. Si no, no estar en el piso del sótano o en el suelo. Deje las ventanas abiertas y que el aire circule a través de la casa. Los ventiladores siempre conectados para que se renueve el aire fresco, de preferencia desde el exterior. Quedarse y dormir en el sitio lo más alto posible, evitando innecesariamente quedarse en las zonas bajas y depresiones del terreno o las grietas causadas por los terremotos. No entrar nunca en viejos túneles o cuevas. No viaje solo, y que los demás sepan de sus planes de viaje. TERREMOTOS – he experimentado un buen número de esos, y puédese volver peligroso, sobre todo en viejos edificios de ladrillo o piedra. Casas de madera o de concreto bien reforzado con acero son consideradas más seguras. Así que la regla es mantener abiertas las puertas a los compartimentos internos (es decir, desbloqueado), porque es menos probable de emperraren (cerradas) y es aconsejable realizar un ejercicio de cómo y dónde salir de la casa o apartamento, si se convierte en inseguro. Pero, sobre todo, quedarse donde está, no correr. Si ocurre un terremoto (5,0 M), póngase de pie en un rincón, debajo de una mesa, o simplemente se pare debajo de una puerta. Esté
siempre atento a la posibilidad de la caída de objetos. Evite tener
las cosas que pueden caer sobre usted en su cama. Compruebe más tarde si todo está bien en casa. Los riesgos de sismos volcánicos son relativamente bajos, los terremotos tectónicos son los que pueden ser peligrosos.
Copyright by Eggert Nordahl. Heimay 1974.
LAS ERUPCIONES VOLCÁNICAS – por lo general las personas no deben vivir en los volcanes. Pero la mayoría de las islas son antiguos volcanes. Ante la amenaza de inicio de una erupción, la mejor cosa a hacer es salir y ir a otra parte. Si esto no es posible, que estéis preparado.
Hay muchas maneras de prepararse. Piense antes. Haga una lista de lo que necesitas hacer y cuándo. ¿Dónde voy a ir, cuándo y cómo. ¿Es seguro quedarse? Piense en los peligros de quedarse. Estas preguntas no pueden ser contestadas aquí. Favor consultar a los planes de emergencia locales (Internet) o encontrar la manera de proceder antes de que ocurra algo.
Si usted no puede ir a un lugar seguro de antemano, por favor, use mi texto sólo como una guía aproximada. Él no es perfecto y yo no soy experto. Mi experiencia viene de la escucha de emisoras de radio del Estado relativas a diversas emergencias y de cómo los demás reaccionan a ellos. Mi formación y experiencia se compone de varios cursos de primeros auxilios y extinción de incendios, así como la búsqueda aérea de aeronaves perdidas, y el transporte y el cuidado de los heridos graves en accidentes por diversos sitios.
La preparación se puede hacer de varias maneras. Una de ellas es
llevar siempre una maleta preparada con algunos cambios de ropa,
pasaporte, tarjeta de crédito / dinero, agua, medicinas, equipo de
medicinas para el tratamiento de pequeños cortes y contusiones, radio portátil (batería) linterna y pilas, mantener la celular cargado con anticipación teniendo siempre el cargador, unos buenos zapatos o botas, gorro de lana y un buen par de guantes, una bolsa impermeable, mantas o sacos de dormir para todos, paraguas, etc … No sobrecargue el vehículo con muebles pesados, o otras cosas innecesarias. Eso puede esperar. Usted puede llevar a algunos documentos personales o cosas ligeras y pequeñas kits de cosméticos o máquina de afeitar eléctrica.
Básicamente, sólo las cosas para viajen, y talvez sea necesario
establecer el límite de una bolsa para cada persona. Mantenga a las
mascotas en sus jaulas habituales (portátil) de viajar y lleve
alimentos y agua para ellos, y también una pequeña cantidad de “comida instantánea” para el viaje. Me refiero a los alimentos que no requieren cocción. Piense en barras de chocolate, etc. Aperitivos, sándwiches, fruta y comidas ligeras pueden ser preparados antes de salir. Tome fotos y una lista completa de todos los miembros de la familia (incluyendo mascotas) para el caso de separación de la familia (se puede guardar en el smartphone). Deje una nota escrita en sus planes de viaje. Salga de su casa en modo seguro (por lo general dejar una luz encendida cerca de la puerta y el congelador / refrigerador en el modo de funcionamiento normal, o desactivarlo si vacío). Desconecte
todos los otros dispositivos, como televisor (removiendo la conexión de la pared, y por lo tanto reduciendo el riesgo de un rayo). Deje encendida la calefacción, para el caso de cualesquiera heladas que pueden dañar la tubería. Mantenga las ventanas cerradas y las persianas seguras. Si usted conduce su coche, mantener el coche revisado de antemano para que tenga suficiente combustible, agua y aceite del motor. Mantenga todo el tiempo las llaves del coche en el bolsillo. Algunos de los elementos mencionados anteriormente se pueden guardar en el maletero del coche de antemano – el coche puede ser utilizado como un refugio, si la casa se daña o vuelva insegura. No corra, conduzca despacio y ofrece paseos para ayudar a los demás, si todavía haya lugar libre en el coche. y ofrecen un paseo a los demás, si todavía hay algo de espacio a la izquierda en el coche. Un consejo que puedo dar si se usa el coche como refugio es dejar que el motor funcione al ralentí durante unos 15 minutos (la calefacción y la carga de la batería) y luego se apaga por 30 minutos (dependiendo de la temperatura exterior). De este modo, se ahorra una buena cantidad de
valioso combustible.
Aquí, en Islandia, sabemos que podemos confiar en Almannavarnir y Radio de Islandia (RUV) para la alerta de anuncios, que son
notificados por las llamadas directas de la Oficina Meteorológica de Islandia (IMO), la policía o los geólogos de la universidad. Los datos de la IMO sobre sismos volcánicos (incluyendo las advertencias) están disponibles en línea y se puede comprobar en todo momento. El sistema es muy eficaz y se usa regularmente. Es parte de la vida normal aquí.
Si algo sucede, los equipos de rescate están en alerta las 24 horas,
todos los días del año en todas las áreas. Y tienen el equipo
necesario, incluyendo jeeps 4×4, motos de nieve, ambulancias,
helicópteros y botes de rescate y patrullaje costero. Hay planes de
contingencia preparados para una erupción del volcán Katla, que se utilizaron en la erupción del Eyjafjallajökull. También el riesgo de tormentas, tempestades de nieve, aludes, rayos, inundaciones,
terremotos, erupciones volcánicas, incendios, accidentes químicos,
accidentes de aviones de pasajeros grandes, etc. Aquí, están siempre pre-establecidas las bases para los servicios de rescate y atención a las personas afectadas – por lo general en las escuelas o la construcción de género y los servicios de rescate y divulgar
Almannavarnir de FM / RUV “Radio 2” (Ras 2) en qué hacer en cada caso.
Ellos tienen toda la información y las instrucciones (no lo tenemos
todo). Confiamos en ellos. Por lo general, se espera por las instrucciones por radio, que pueden dar pistas importantes sobre lo que está sucediendo. No utilice el teléfono celular y evitar hacer
llamadas innecesarias. Ahorro de energía, si es posible. Mantenersezona segura es la mejor cosa que hacer.
ISLANDER (Translation by Renato Rio)
Updated with 2 videos Islander recommended by Spica
The ironically named Mount Eden, near downtown Auckland.
Most people in the world agree on one thing: it is safer to live far from a volcano then it is living right on top of it. Living next too, or on top of a volcano is like sleeping in a cave with a friendly bear. Sure, it has it’s advantages, you stay nice and warm, you don’t have to worry about other predators, a good part of the year it is nice and quiet, but still….. you know that some day he will grab you and eat you. The inhabitants (some more permanent than others) of Herculanum, Pompeï, Heimaey and the Hawaiian Royal Gardens have found out the hard way.
New Zealand is, apart from being stunningly beautiful, one of the least populated countries in the World. When Western settlers arrived they could have chosen any location to go and build large cities. For some reason however, the inhabitants found it neccesary to build their largest city directly on top of a volcanic field with about 50 scoria cones, maars and tuff rings dotting the landscape. I suppose the knowledge of volcanism was not as developed back then as it is today, but nevertheless it is quite unfortunate.
Photograph by Mollivan Jon. Mount Taranaki.
New Zealand is dominated by subduction volcanism, with famous Mount Taranaki (or Egmont) as one of the most visually stunning stratovolcanoes in the world from both the ground and above, and with the infamous Taupo Volcanic Zone, best known for being one of the worlds “super” volcanoes. At 250 km from Auckland this is already quite a hazard on itself.
The Auckland Volcanic Field is a monogenetic volcanic field, meaning that an eruptive episode only happens once through a vent. Each eruptive episode generates a new vent somewhere within the volcanic field as opposed to “normal” volcanism where a volcanic vent has succesive eruptive episodes causing a volcano to build up and blow up occasionaly. The Auckland Volcanic Field produces basaltic scoria cones, maars and tuff rings (with the exception of the island of Rangitoto which erupted several times). All three are caused by the same type of magma, basaltic magma in this case, but the location the surface penetration, the eruptive flowrate and the total volume of the basalt determine the type of surface expression. The volcanic field has been active for about 150.000 (0.15M) years now. Older volcanic fields are found towards the south; South Auckland (1.5-0.5M), Ngatutura (1.8-1.5M) and Okete (1.8-2.7M).
The source of the basalt is not quite clear however. Basalt is normally not associated with subduction volcanism. Petrology and earthquake data have practically ruled out the possibility of the lava having an origin in melt generated by the subducting Pacific Plate. The Auckland volcanic field also sits some 200 km behind the active volcanic front of the Taupo Volcanic Zone. Furthermore, there is no evidence that the subducted Pacific plate reaches all the way to the Auckland volcanic Field.
Basalt is usually associated with mid-oceanic ridges/spreading centers or hotspot volcanism. Again, petrology has not been able to find much evidence for hotspot volcanism either. Additionaly, the propagation of the volcanic fields is directy opposite to the relative motion of the plate; the oldest volcanic field should have been in the north and the youngest in the south if a hotspot or mantle plume was involved. It is possible that the complex geology with major plates subducting, twisting and turning in the area is causing localised decompressional melting , leading to magma migration upwards right below the city of Auckland. There is some extention ongoing in the area, so this seems like a plausible explanation.
The Pacific plate and the Australian plate in a complicated geological setup
This image shows the subdution margin, the strike-slip faults to the southwest and extention(volcanic back-arc) to the northwest of the subduction margin.
Monogenetic volcanic fields are very interesting and highly unpredictable. The eruptions are not very large or extremely violent, but they can occur pretty much anywhere within the field at any time. With a large city with hundreds of thousands of inhabitants spanning the field, this is exactly what you don’t want. Paricutin in Mexico is the most famous example of this type of volcanism. One day you are happily working your crops, the next day you have to flee from your land because a volcano decided to take over your land. Bad luck, deal with it. Any new eruption within the Auckland Volcanic field will have as much compassion with buildings, streets, highways, parks and emergency shelters as Paricutin had with the crops that were growing there. This is what makes Auckland a relatively dangerous place to live in because it is not clear how much warning time there will be and how accurately the location of an eruption can be predicted with modern equipment.
The reason why new volcanoes pop up at random has to do with the generation of the magma. It is important that the generation occurs very slow. Slow enough to be unable to build a plumbing system that would efficiently conduct the magma to surface. Every new, hot, fresh slug of magma finds it’s own path to the surface, erupts and that’s it. The conduit cools and is no longer usable for the next slug of magma that arrives several decades or hundreds of years later below a slightly different part of the volcanic field. There is not enough magma flowing into one area to create a magma chamber in which the magma can evolve and produce more silicic types of magma.
Ridiculous in Los Angeles, not so ridiculous in Auckland. Bring out Tommy Lee Jones!
We have all seen the Hollywood movie “Volcano” and no doubt that many Los Angeles citizens have had a very good laugh at it (the La Brea tar pits are the surface expression of a leaking oilfield through a fault, it has nothing to do with volcanism whatsoever), but for the citizens of Auckland, those images are not even very far from the truth. The past gives an excellent example of what can happen. The next eruption in the field will most likely follow this scenario:
1 – Magma is forced upward through weak points in the crust.
2 – Either the magma contacts ground-water, or reduced pressure near the surface causes gases to bubble out of solution. The result is a phraetic or steam-blast eruption. The heaviest material is thrown out horizontally to form a tuff ring. Lighter material is blasted vertically to form an eruptive column. After a few days, weeks or months, the volcano falls quiet. Several of Auckland’s volcanos became extinct at this point.
3 – Additional magma may rise in the conduit. If enough magma is supplied, fire fountaining starts through one or more vents. Small lava flows may be produced, which do not escape the tuff ring. Sometimes the eruptions build scoria cones.
4- If fire fountaining continues beyond this point, the scoria cones can coalesce to rise and bury the tuff ring. Lava flows can also fill the surrounding valleys.
5 – Sometimes the outflow of lava is so great that it undermines the cone, which collapses into the flow and is carried away, leaving a horseshoe-shaped breached crater. If lava flows for long enough, nearby valleys are totally filled in and the lava floods the entire area with a large sheet.
Isn’t that just wonderful right in your own neighbourhood?
Map showing the city of Auckland and the eruptive centers.Pick your favourite spot to build your house.
The big question that remains is then: When is the next eruption going to be? Well, you will have to chop off one of the arms of a geologist to get a clear answer on that, but there are usually several hundred to several thousand years between eruptions in this field. The last one was about 600 years ago, so it might be a while before it is “overdue”, but it might be soon as well.
