Previously, Carl has pointed out just how lacking the VEI scale is.
VEI is based off of the total quantity of material that came out of the hole. In this respect, not a bad scale… but VEI means “Volcanic Explosivity Index.” What about the less energetic eruptions? Say, Kilauea? How about a volcano that makes a big show at first then oozes magma for a year afterwards? Eruptive sequences generally include the entire time that stuff is coming out of the ground, and in order to compare one eruption with another, one of the best comparison is by how much came out. VEI will be with us for some time, but it helps if you have some context as to what it means.
Eyjafjallajökull was out paced by Grímsvötn in about a day. Grímsvötn is a true monster, and fortunately for us, all it did was one of it’s lesser burps.
Here is a plot of volcanic plume height over a period of hours, and how much material, in “Dense Rock Equivalent” (DRE) that equates to. The formula was derived from Mastin et al, who essentially did an update on Sparks’ equation. The purpose was to get an estimate of the eruptive rate of a volcano based on sporadic or sparse information… such as only having plume height data of a remote volcano off in the middle of nowhere.
Image by GeoLurking. Click for larger image.
As you can see, for a sustained plume height at the indicated level, the mass adds up over time. As time goes on, eventually different levels of VEI are reached.
You can also see how Grímsvötn blew the doors off of Eyjafjallajökull’s “puny” eruption.
In “A multidisciplinary effort to assign realistic source parameters to models of volcanic
ash-cloud transport and dispersion during eruptions” L.G. Mastin et al there is a formula that allows a computation of the mass ejection rate based on plume height.
It’s geared mainly towards volcanoes located in remote areas (such as Cleveland) and proves to be a handy tool if you put in a little work.
VAAC reports are probably the most handy reports available for any given eruption. VAAC is most concerned about keeping aircraft from plummeting out of the sky, so they try to stay on top of the hazard. This also means that their reports, though good, are more focused on the threat than the volcano. What the volcano is actually doing is little concern for them… what it did do is the most important. This means that once a plume is lofted into the air, the max elevation of the plume sort of remains fixed until it dissipates. The threat envelope will move around with the cloud… and generally the max elevation will remain mostly fixed.
If you are lucky, the VAAC report will state somewhere in the warning what the plume height is over the volcano. That is the data that a volcanophile will keep track of. That gives you the current state of the eruption.
Taking the time stamps for each report, along with the height of the plume over the volcano, and adding in the heights and time stamps from what ever geological agency reports, you can get a pretty decent record of the activity levels, and make a rough estimation (using Mastin et al) of the total amount ejected.
You do this by interpolating the rate from one data point to the next. You could connect the dots using a straight linear trend, or you could use some sort of poly curve or cubic spline (what ever your spreadsheet or data fitting program is capable of). From this curve, you need to get the interpolated increments down to one second intervals. Once you have interpolated timestamps and the estimated column heights at those moments in time, apply the Mastin formula to determine the DRE rate.
Then you just sum those rates in order to fabricate the total amount erupted to that point in time.
It may sound complicated, but it’s pretty straight forward.
From Mastin et al
H = 2 * V^0.241
Solving for V
V = (H/2)^(1/0.241)
V = Rate in m³/s
H = Height in km.
And.. a very important caveat… the formula has an error envelope of a factor of four. That’s pretty large, but it gets you in the ballpark for eruption estimates.
A sample run:
This is about a fictional volcano. Since it’s my construction, I choose to name it Mt. Gibbons. (I’m a Billy Gibbons fan) On 1/15/2012 at 12:00, Mt. Gibbons erupted to an initial altitude of 15 km. A compilation of VAAC reports and eyewitness reports from the Soso MS Volcano Observatory, show this for Mt Gibbons activity (plume height)
Calculating the number of seconds since the start and re-plotting, we get
Now we apply the Mastin et al derived equation, this gives us the rate of the eruption.
This is where I cheat. Using the built in integrated function of Dplot, I have it calculate the integral. You can do something similar with your spreadsheet program if you calcuate the linear trend between each point, then put together a running sum of those calculated points.
So.. as you can see, Mt Gibbons, starting to wane in activity at around the 24th of Febuary, will probably come in as a solid VEI-4. One thing that is very important, is to remember that the reference document, Mastin et al, clearly stated that there is an error factor of about four in the equation. In other words, this will get you into the ballpark, but it’s not full proof.
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
This will just be a short update with the information that has come at hand.
There seems to be a full on war between Pevolca, Involcan and José Luis Barrera VP of the ICOG (Spannish Association of Geologists). Pevolca has stated that there are some reneval of tectonic earthquakes, with no risk for the population or any need for any measurments to be taken. They also point out that there is no increase in gases. They do though mention that they will be watching things. They have also stated that there is no inflation at El Hierro (GPS).
Involcan has stated there is inflation after studying the GPS system of Professor Sagiya from Nagoya. They also point out that the reason for Pevolca not being able to see any heightened gas levels is that they have not measured the gas since April 5.
José Luis Barrera and the ICOG have issued a statement that the more than 350 earthquakes are tectonic, but that they might be a run-up phase for renewed volcanic eruption. They also note that the activity is unusual.
While the Spannish authorities and organisations are involved in their usuall pissing contest there are some things worthy of comment.
A little tidbit on the earthquakes during the 48 last hours…
Yesterday had the fifth highest recorded number of earthquakes (241), the highest recorded number is close to 454, and that was in August as the former wad of magma had it’s peak of arrival.
But what is really interesting is that if one take a look at how those quakes break down into size…
Yesterday first, then August number-record.
0-2M 55 (448)
2-3M 180 (6)
3<M 8 (0)
And that would have made yesterday into releasing 5 times as much energy and destroying about 32 times as much rock. It was the record of all time energywhise. This leads me to believe that the amound and speed of arrival is higher this time around. So, the last two days have had the largest accumulated seismic energy release since onset of activity at El Hierro. Energy record in short. And that is note noteworthy according to Pevolca.
LP Earthquakes
The earthquakes today has long amplitude component to them normally associated with magmatic movement into the cracks. These LP earthquakes is considered to be magmatic. There has during the last 8 hours been at least 3 of them. The 17.16 is one of them.
I believe this is onset of movement upwards of magma into the actual system of Tanganasoga.
First LP
Image by IGN. The First LP Earthquake.
Second LP
Image by IGN. The Secong LP Earthquake.
Third LP
Image by IGN. Third LP Earthquake, and what is most likely onset of a heavy magmatic intrusion upwards.
The third LP seems to have opened a conduit somewhere, most likely from the crustal boundary (MOHO) up to the chamber under Tanganasoga, or directly towards Bob. The Long Periodicity Earthquake is caused by an initial earthquake that opens up a fissure, sill or dyke, after that magma moves in to fill the opening, and that creates and unusual type of earthquakes.
Conclusion
There is no reason that I should recant on what I wrote yesterday. I still believe that there is a rather high risk of a new eruption at El Hierro. I still see no reason to not believe it will be in the southern part of the island, or out in the ocean south of La Restinga. I still feel that La Restinga is not entirely safe for it’s population.
Update
While I was writing this post the signal changed sufficiently for me to believe that there is risk that the eruption is either about to start, or has already started. We are all waiting for news, and think about the unprotected civilians in El Hierro.
The earthquake that started either the pre-eruptive run up, or a new eruption.
On the seventeenth of June a new phase of increased earthquakes was observed by commentators on this blog. The level of seismicity was both larger and more numerous than during the previous 3 months. The location of these earthquakes corresponded with the place where the first earthquakes happened during the run up to the previous eruption.
As I have said before, when new magma comes up from the deep via the mantle plume we would see earthquakes at this spot. On the twenty-second of June low frequency harmonic tremor started at two distinct frequencies (0,29 and 0,59Hz) that previously has proved to be related with renewed activity. The frequencies are believed to be a sign of new magma arriving from the deep.
At 21.23 hours on the twenty-fourth of June (yesterday evening) an earthquake of magnitude 3.1 occurred, and within minutes the harmonic tremor had increased in sufficient numbers to herald movement of magma up the magmatic conduit system. After that there has been 49 earthquakes ranging from 2M to 3.8M, which is a rather good sized earthquake swarm for an already active volcanic system.
It has been noted that the earthquakes are not at the exact spot where they were during the previous eruptive phase. The answer is rather simple, the previous earthquake loci have by now gone above the solidus point and is not any longer brittle enough; therefore the renewed pressure breaks the adjacent rock. In other words, the magma chamber has matured and evolved.
As the pressure started to build up from the recently arrived new magmatic material from deep it started to move towards the old conduit. This conduit is by now fairly blocked by solidified magma at the opening.
A renewed eruption will start somewhere along the old conduit leading south from the Tanganasoga volcanic system towards the old eruptive vents that build up the edifices of Bob south of La Restinga. The question is if the new eruption will take place at the original pillow lava and pumice cone of Bob, or up at the new vent slightly closer to La Restinga. Another option is that the old vents by now are to plugged for the lava to be able to escape that way. Then the most likely place is somewhere along the route of the old conduit. And that means closer to the town of La Restinga, or even on land close to or inside the town.
Currently I would say that there is a high risk of an eruption starting, or that it already has started. Visible signs of the eruptions should be coming within the next 3 days judged on previous behavior. The eruption will most likely not be larger than the previous one due to the pressure being lower, but if it happens closer to shore, or even on land, the effects might be more dramatic for the residents.
My judgment would have been to immediately evacuate La Restinga until the eruptive locus has been confirmed.
IGN and Pevolca has declined to comment on this.
Update:
Regarding why I wrote that unusual and stark warning directed to the residents of La Restinga. I want to clarify why.
1. From the current signs and previous behaviour of the Tanganasoga volcanic system I judge that there is a 2/3 risk for a new eruption soon.
2. I am fairly certain that Bob and the newer vent on the ridge above Bob towards La Restinga is congested by solidified lava and not viable any longer as eruptive vent.
3. During the end of the previous eruptive phase there was anomalous gas ventings closer to La Restinga, and 2 earthquakes located close to the port of La Restinga (one was inside the actual port).
4. We know that the conduit leads from Bob towards a magma chamber under Tanganasoga. The usual behavious for volcanoes of this type is propagating vents erupting ever closer to the central part of the volcano.
5. From all of this I judge it to be about a 50 percent risk that the new eruption would be sufficiently much closer to La Restinga to cause risk for the inhabitants, or even on land close to or inside La Restinga. One should remember that there is a scoria cone 100 meters outside of La Restinga.
6. The current harmonic tremor episode is of the broadband type that is normally associated with sudden heavy degassing caused by the earthquakes. This can in a few eruptions increase the likelyhood of a non benign type of eruption. Ie, that the next eruptive phase may be having a more vigorous start than the previous due to a lot of gas pressure building up.
7. IGN and Pevolca is not the most warningsome agencies on the planet, to put it mildly.
All of this put together gave me a bit of a judgement call crisis. Based on my consciense, my experience, and so forth I decided that someone should issue the warning that IGN and Pevolca most likely will not give. So, I gave a warning that I myself would adhere to. I personally would not be inside of La Restinga right now. I would rather have someone say I am an idiot and should shut up, or even in the end try to sue me, than feeling that I through being quiet was part in people dying.
I would though like to say that those who so far have questioned me (privately) have been quite correct in doing so, specifically since I was in a hurry when writing and therefore a bit vague.
Pevolca has notified that there will be a statement after their meating this afternoon, and also commented that the afternoon today was the fastest possible oportunity for the meeting regarding the current new activity.
Update 2
People have noticed down in the comments that the harmonic tremor is higher in frequency this time and look different. That is because it does.
Click on the image for a bigger view. Do not be alarmed by the text, what is stated there is about volcanoes that have had a long repose period.
The earthquakes have knocked off a lot of gas from the lava, and this causes something called a Broadband signal. These are normaly associated with more vigorous eruptions. The text in the image states the limit here as being a VEI-3 eruption following a broadband signal. But that is for a volcano that has been dormant for a while. At Tanganasoga the plumbing system is still in large parts open, so the pressure can not build up sufficiently to produce a VEI-3 eruption, and that most likely gives the broadband signal for a smaller possible event.
