Category: Swarm

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The weekend earthquake swarm deep out on the Reykjanes Ridge

During the weekend there was as earthquake swarm deep outside on the Reykjanes Ridge. It was about 700 km south of Reykjavík city. It was not felt on land and was only noticed on instruments. The last earthquake to be recorded was at 22:04 UTC, on 20 November 2011. It’s size was Mb4.4 according to EMSC. The largest earthquakes in this earthquake swarm had the size of Mb4.8, but there where several earthquakes recorded with this size.

Due to the location it is impossible to know if there was a eruption in this area or not. The ocean depth there is greater then 1 km (if my memory is correct). This means that if a eruption is taking place in this location. Nothing is going to appear on the surface of the ocean. So why this earthquakes are taking place are only speculation everything besides normal tectonic activity in this area. But the Reykjanes Ridge is a rift zone that often has earthquakes without any eruption taking place. There have however been several earthquake swarm during the year in this location. But what the actual reason remains a mystery due the location.

Other then this it is now quiet time in Iceland. This is the type of quiet time that I always worry about. But lets wait and see what is up with this lack of activity in Iceland.

Note: Update on the eruption in El Hierro volcano eruption is due tomorrow. This is now a long term eruption as explained few blog posts ago. So there are only updates on what is going on once in a while.

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Possibility of a new fissure has opened up in El Hierro volcano eruption

It seems by the harmonic tremor data that a new erupting fissure has opened up somewhere in El Hierro volcano. But given lack of visual observation I do believe that this fissure is at really great depth, and is not leaving any signs on the surface that a new eruption is taking place. Where this new fissure might be is unknown to me at present time. But based on the harmonic tremor data this new eruption seems to be powerful one. It should be expected that new fissures opens up a random while El Hierro volcano is erupting. So far the fissures that have been opening up have been short and out in the ocean. It should also be expect that erupting fissures stop erupting for no reason and with no warning at all. This seems to have happened as I am writing down this blog post.


The harmonic tremor from the eruption in El Hierro volcano yesterday. It can be seen on this harmonic tremor chart that the eruption was powerful all yesterday. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).


The harmonic tremor around 22:07 UTC. At that time the eruption was in full power as can be seen. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).


The harmonic tremor at 22:46 UTC. Notice how the drop is sudden when the new eruption fissure stops erupting. What happens is that the magma source that fed the erupting fissure did dry up. Why and how that happens in unknown to me. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).

This might mean that a new fissure might open up in the next few hours to days. Where that might happen is impossible to know. But as the fissures have been open up so far, it is going to be in a North – south line (about) in El Hierro volcano. What has however become a problem in my opinion is that the magma might have “boiled” the rock and made it soft. So it might not make a earthquakes before a eruption starts in it. This might be the case if the magma has been in the crust for the past 5 weeks. But the only example of that type of event that I know of was in Eyjafjallajökull volcano last year (2010), when a new fissure did open up suddenly and without any earthquakes or warning after 4 weeks of eruption. The reason for that was the same one on what I think might be happening in El Hierro volcano.

From what I can tell, based on data and earthquakes it does not seems that the eruptions in El Hierro volcano are over. As new magma continues to flow in from depth (the mantle). Until that flow stops, El Hierro volcano is going to continue to erupt. However there might be breaks from few hours and up to several weeks between eruptions, in that case no eruption would be taking place. This has its origin in the fact that this is a fissure rift events of shorts, a similar eruption took place in Krafla volcano in Iceland for over a 10 year period. Movement and flash inflation and deflation are also to be expected during this period in El Hierro volcano eruption. As it has many similarities of the eruption in Krafla volcano in Iceland. But it is not exactly the same, just similar. As Krafla volcano is on the inter-plate rift zone. While El Hierro volcano is on a hot spot rift zone, far inside the Africa Plate.

Update on the forum: There have been some technical difficulties with the whois registration. How that works out is not yet clear. I am going to short that issue out before I set-up the forum on the domain. In the case I have to register a new domain name. What happens in this case should be come clear next week I hope.

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Katla volcano newest earthquake swarm

During the night of the 16th of November, 2011 there was a new earthquake swarm in Katla volcano. This earthquake swarm is a part of ongoing pattern in Katla volcano. This pattern started after the small eruption that took place in Katla in July 2011. It was observed yesterday that there was a deep earthquake in Katla volcano, with the depth of 28 km. This earthquake did most likely did happen due to a dike intrusion deep inside Katla volcano, but it might well be that this was just a normal earthquake. It is hard to know that for sure. But deep dike intrusions are well known in Katla volcano. Sometimes they are followed by a harmonic tremor for few moments or minutes.


The earthquakes from Katla volcano can clearly be seen on this tremor plot from Iceland Met Office. But they make the spikes that are on it. Copyright of this picture belongs to Iceland Met Office.


The location of last earthquake swarm in Katla volcano. Most of the earthquakes are inside the caldera of Katla volcano. Copyright of this picture belongs to Iceland Met Office.


The largest earthquake in this earthquake swarm. Its size was ML2.35 and it had the depth of 4 km. This picture is released under Creative Commons Licence. Please see the top bar (there is a link there) for more information on this.

This was a long period earthquake. But this is the only clue at the moment that Katla volcano is going to erupt soon. But when is still a unknown question at present time.


The frequency analysis of the ML2.35 earthquake. As can be seen here this earthquake has really low frequency component. But most of the energy goes into about 2Hz frequency. This picture is released under Creative Commons Licence. Please see the top bar (there is a link there) for more information on this.

It is impossible to know how many earthquake swarm Katla volcano is going to have before it erupts. But this is a one way street that Katla volcano is now on. For us humans, we just have to wait and see what happens next. Nothing else can be done when it comes to forces of nature. When the time comes, get out of the way of Katla volcano.

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Analysis of the earthquake pattern in El Hierro volcan

Please note that this is not a professional analysis of the recent earthquakes in El Hierro volcano. So it might be wrong. It also might not hold any science value at all.

During the eruption of El Hierro volcano a earthquakes activity has been in the north part of El Hierro volcano. This earthquake activity is most likely created by dike intrusions into the bed rock. At this moment it is unclear if any of them are going to reach the surface. There also seems to be some minor connection between the earthquake swarms and how active the eruption is in the south part of El Hierro volcano is. But what and how that connection is and works is unknown to me at present time. The strongest earthquakes that have happened so far are up to Mb4.6 in size (I do not think that this earthquake size has been downgraded. But I might be wrong).

The current location of the earthquake swarm has not changed a lot during the past few weeks. So it is more or less in the same place. There are however reports that the earthquakes are getting shallower. But it is currently unknown if that is because of magma movements or because the crust is releasing stress because of the dike intrusions in El Hierro volcano. A full list of earthquakes larger then ML2.5 can be found here (EMSC).

The results of this dike intrusions are going to that in some areas of El Hierro Island a hot springs and other types of hydrothermal activity might show it self. Without warning. But that can result in this type of hot springs.


Picture is from Hveragerði, Iceland. Picture taken by me (Jón Frímann Jónsson). This picture is released under Creative Commons Licence. See Creative Commons Licence web page for more details (link in top bar).

This is also going to be the result for El Hierro volcano after the eruption end, if any magma remains shallow in the crust to cool down.


A 48 hour map of the earthquake activity in El Hierro volcano. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).

The earthquake are in almost N-S line, that is most likely the fault line that might erupt if it opens up. But as it stands now. Most of it would be out to the sea. But the exact length of a fissure is impossible to predict. What happens is only clear when it starts erupting.


The 4 day amount of earthquakes in El Hierro volcano. There are some earthquakes in south El Hierro volcano. But those earthquakes are fewer and smaller in size. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).


The total number of earthquakes in El Hierro volcano since the magma intrusion started in July 2011. As clearly can be seen on this picture, the new area with earthquakes makes a clear signal that it a magma injection into the rock. Rather then result of tectonic movements in the area due to the eruptions. Copyright of this picture belongs to IGN (Instituto Geográfico Nacional).

Update on the eruption it self: Explosions appears to be taking place in El Hierro volcano again. That suggests that the eruption is once again more powerful, after a few hours of lowered activity. It is not yet confirmed if any new vents have opened up closer to the shoreline. There are pictures that suggest it. But nothing is confirmed at this moment. But it cannot be ruled out that new fissure is going to open up closer to the coast. If that happens, it is going to be noticed if the depth is shallow enough.

As for the eruption in El Hierro volcano. I now classify it as long term eruption, as it has lasted for longer then 1 month. So rather then sharp blog posts about what is going on. I am going to post regular updates on what is happening in El Hierro volcano eruption. If there are any major changes. I am also going to cover that soon as possible. But I am not always in front of the computer, and El Hierro volcano is far away. But I am doing my best regarding this eruption.

Blog post updated at 12:25 UTC on 16 November, 2011

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New dike intrusion into Katla volcano caldera

A new dike intrusion has started in Katla volcano caldera. So far only few earthquakes have taken place. But the largest one so far is ML2.8 in size with the depth of 0.8 km (800 meters). It appears clearly on my geophone at Hekla volcano. But it seems that new area in the Katla volcano caldera has been increasing activity during past few weeks. Based on the number of earthquakes that are currently taking place there.


The earthquake as I did record it on my Heklubyggð geophone. This are all the directions on the gephone. This picture is released under Creative Commons licence.


The North-South component of the geophone shows the nature of this earthquake clearly. This picture is released under Creative Commons licence.


The vertical component of the geophone did also show the nature of this earthquake clearly. This picture is released under Creative Commons licence.


The area inside Katla volcano caldera that is responsible for the current earthquake activity. Copyright of this picture belongs to Iceland Met Office.

The earthquakes in Katla volcano now are created by magma intrusion into the rock layers. There is not a lot of about tectonic earthquakes in Katla volcano today. But they cannot be completely ruled out. But the signature of those earthquakes is different then by earthquakes created by magma movements.

Note: I have been recording earthquakes since the year 2006. I have learned a lot during that time.

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Update on the eruption in El Hierro volcano on 9 November, 2011

Short note on comments: This is a short notice on comments. This blog has been getting a spam flood for the past few days. During the past 2 days or so there have been over 300+ spam comments that my spam filter has captured. This makes it ever so hard to find real comments that go into the spam box by accident. If your comment disappears for no reason after it has been posted. Then the spam filter has captured it. Please do not re-post it, as then following comments are just going to go into the spam box too. I have to manually un-check them as spam and approve them. So if you post three comments with the same link, I am going to clear the three comments with the same link. But given the amount of spam that this blog is getting there is always a risk that comment is going to get lost and permanently deleted.

It is also important that if you get “comment is held for moderation” that you do not re-post what you are commenting on. As the comment is going to wait in the moderation until I clear it. I am not always around to check for this, so it might take few hours or more until I approve the comment/s.
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The eruption in El Hierro volcano is ongoing and does not appear to show any signs of ending. However the strength of the eruption has dropped a bit during the past two days. But this was to be expected, since this is a fissure eruption and it has mostly been erupting from the same vents during the past four weeks.

It has become a bit difficult to get accurate information on what is going on El Hierro Island. So I am not going to speculate on that. But from what I can gather it seems that dangerous gas level has been detected on the ground. But the reports that I am reading are bit unclear on this. This has also been mentioned in comments on this blog.


The harmonic tremor from the eruption in El Hierro volcano at 15:23 UTC on 9 November, 2011. Copyright of this picture belongs to IGN.

As can be seen on this tremor plot the harmonic tremor in the eruption is dropping. Explosions that have taken place are also clear on this tremor plot. That might be because the eruption vent is getting smaller, therefor less magma is being push out the erupting vent. Or the currently erupting vent might be closing up. As so often happens with fissure type eruptions. If that happens does not mean that this eruption cycle is over. It just means that the current eruption vent has closed up. New fissures are most likely to open up in coming weeks as the eruption goes on. Where and when it impossible to know for sure.

Earthquake activity continues in north part of El Hierro volcano. This are most likely dike intrusions into the bed rock there. So earthquake activity should be expected to continue north west of the town Frontera. If a dike intrusion manages to find a path to the surface in this area there is going to be a eruption and earthquake activity should drop following that. But until and if that happens there are going to be earthquakes. There is also chance of hydrothermal activity to show up in this area if a dike intrusion gets shallow into the bed rock. But is not go up from the ground and start a eruption. This might also be the reason why some part of El Hierro Island are experiencing high levels of toxic gas for the moment.

I am going to post more on the eruption in El Hierro volcano as I know more what is going on.

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General update for Katla volcano and El Hierro voclano

This is a general update for Katla volcano and El Hierro volcano.

Katla volcano, Iceland

During the weekend there was a minor dike intrusion into Katla volcano caldera. The largest earthquake in this earthquake swarm was a ML2.1 with the depth of 1.4km. This is among the smallest earthquake swarms in Katla volcano since activity started to increase after the small eruption in July 2011. The reason for this earthquake swarms in Katla volcano are dike intrusions (wiki). Sometimes following this are small glacier floods from Mýrdalsjökull glacier that is on top of the caldera. But that does not seems to have this time around, or the last time there was a dike intrusion in Katla volcano (few weeks ago).


The earthquake activity in Katla volcano during the weekend. Copyright of this picture belongs to Icelandic Met Office.

El Hierro volcano, Canary Islands, Spain

The eruption in El Hierro volcano continues as it has been doing for the past four weeks (almost). But the chance of a new island forming has grown somewhat in the past few days. The main reason for that is that eruption did gain some strength during the past two weeks. The increased strength in the eruption was due to a new injection of magma into El Hierro volcano. Both at the main magma sill and what seems to be a new magma intrusion into El Hierro at depth. That magma has so far not been able to reach the surface and remains at the depth of 20 km or so. But there also seems to be some dike intrusion activity been taking place in the same area, as more magma is injected under El Hierro volcano North West of the town of Frontera (IGN name information).

For that reason the risk of new eruption vents open up in this area is high in my opinion and is going to remain that during this eruption. But it remains to be seen if a new eruptions vents open up in this area. But that depends on the amount of magma that is currently injecting into El Hierro volcano at depth. It is impossible to know for how long new magma is going to get supplied into El Hierro volcano. But so far this process has been ongoing since July, so that is already five months (or about that) that new magma has been flowing into El Hierro volcano.

The formation of new Island off the coast of El Hierro Island is now a real chance. As the erupting vent has build up close enough to the surface of the water to start the Surtsey Island process. That process in it self is going to take few weeks to complete, at least until the crater no longer gets water into it. When the water can no longer into the crater the eruptions turns to lava fountain eruption. A Hawaiian style of eruption to be exact. That progress is going to remain to the end of eruption. But this is only going to happen if the eruption lasts long enough to build a small Island off the coast of El Hierro Island. So far that remains unseen. However the chance for this to happen is good in my view.

There is also worth noticing that this eruption is a bit variable in eruption strength. This can clearly be seen on the harmonic tremor plots that can be viewed online from El Hierro volcano. This is normal, as the flow of magma from inside El Hierro volcano is not stable and can change suddenly. The risk of new fissures to open up without warning remains high in the area around the current eruption vent is also high. The new fissure have the risk of opening up without any earthquakes and warning. To some extent this has already happened during this eruption. But I am not sure the new eruption vents did stay erupting for a long time. This is however most likely to repeat it self regularly during this eruption.


The harmonic tremor in El Hierro volcano on 7 November, 2011 at 09:32 UTC. Copyright of this picture belongs to Instituto Geográfico Nacional.

Off topic: Small apology

Here is a small apology to my readers. I have been a little bit under the weather in past few weeks. There are many reasons for this. But the biggest one is that my plan to live in Denmark failed this summer. But the chance of me moving back to Denmark has lifted my mood again. But I also found that playing computer games helps me dealing with my current status a bit. Because of this under the weather issue. My blog post have not been that good in my view. For that I want to apology. I can’t promise that this won’t happen again while I am living in Iceland. It is also a factor that the darkest time of the year never goes well with me (Mid October to early March).

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El Hierro volcano enters Surtsey eruption phase

This is a short blog post about latest events.
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Earlier tonight a Surtey eruption started in El Hierro volcano. Before this phase did start there has been increased harmonic tremor on seismometers that are located on El Hierro Island. Volcano ash is to be expected while water can still get into the crater. When the water does no longer get into the crater it is going to stop making volcano ash. The ash plume can go up to 3 to 10 km high, depending on the strength of the eruption. New vents have also been opening up south of town of La Restinga. That means the fissure is still growing, at least that was the case yesterday and earlier today from what I can gather. I am unsure of that has continued or stopped.

Earthquake activity still high north west of the town of Frontera. This suggests that fissure might open up there. But so far that has not happened. I do not think this are earthquakes due to tectonic stress changes due to the eruptions in south El Hierro volcano. But this stress changes are because of the magma injections at depth in El Hierro volcano.


Harmonic tremor from the eruption in El Hierr volcano. It now shows clear signs of explosions (strong ones) and increased eruption activity. Copyright of this picture belongs to Instituto Geográfico Nacional.

If new vents open up closer to the shore there is going to be instant Surtsey eruption activity. But that might only last for a short while the water gets into the crater. There the lava stage is reached much sooner then on the vents that are erupting on more depth at the moment.

I am going to post more updates on this. If I can get more details on what is going on.

Sources:

Renewed Eruptions at El Hierro in the Canary Islands (Eruption blogs)

I also want to thanks reader how email me about the current status of what is going on in El Hierro volcano. My Spanish is weak at the moment.

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Short update on El Hierro volcano eruption

This is a short update on El Hierro volcano eruption. As the situation is changing fast this past few hours.

It seems that the eruption in El Hierro volcano is gaining strength and power. The harmonic tremor on the seismomter that is on the El Hierro Island it self has started to get saturated again. It also have been unconfirmed reports of the south fissure growing in size. But so far nothing has happened in the north part of El Hierro volcano. Even if there have been many earthquakes in that area. But this area fell suspicious silent this morning. So something might be up in that area. Update 1: A string of earthquakes happened around 12:00 UTC in this area. Suggesting that something is still up there.


The harmonic tremor at 13:52 UTC. Notice how the tremor has started to saturate the seismometer. Copyright of this picture belongs to Instituto Geográfico Nacional.

What happens next is anyone guess. But people need to be aware that fissure eruptions are sometimes long in terms of the length of the fissure. But that phase normally does not last long, as soon the eruption is going to isolate it self into few craters on the fissure. I also recommend that people read Erik Klemetti blog post about El Hierro from yesterday. If you haven’t already done so.

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Increased eruption activity in El Hierro volcano

I was going to post this yesterday. But I fell a sleep at 17:00 UTC and I didn’t wake up until 03:00 UTC.
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The eruption in El Hierro volcano continues as it has been doing for past few weeks with little change. The first eruption vent that did open south of El Hierro Island has continued to erupt. But so far no Island has formed and it is unclear if it is going to form, as the depth is great in this area. Since yesterday around 06:00 UTC the harmonic tremor has been increasing. But this suggests that new vents have opened up in the south eruption area. I got some pictures of that yesterday in the email. But they did not show anything new in my view. Thanks to the readers how did send me those pictures.

The current fluctuation in the harmonic tremor from El Hierro suggests that magma is on the move in the north part of El Hierro Island. Both off the coast and maybe inland on the Island where earthquakes have been taking place. It is impossible to know how this is going to develop during the next few hours to days. As that depends on the rock structure of El Hierro Island and earlier eruptions.

Earthquake activity

During the past two weeks the earthquake activity have been growing in the North-west part of El Hierro Island. The reason why this is happening is that a new fissure is about to open in this area. As I have mentioned before in earlier blog posts. When and where is impossible to know for sure. The largest earthquake so far took place this morning, it size was ML4.0 with the depth of 20 km. But this is the automatic data from IGN. This pattern of earthquake activity is most likely going to continue during this eruption process in El Hierro volcano. Since the eruption type here is a fissure eruption.

It is worth noting that earthquakes in once place does not mean that the eruption is going to happen in that place. As the magma can travel in dikes all over the El Hierro Island and show it self anywhere on the Island it self. So the general risk is high in my opinion. The only action that can be taken is to be prepared for sudden eruption of new vents on El Hierro Island. Since there is a good amount of magma on the move inside El Hierro volcano.


The harmonic tremor in El Hierro at 08:54 UTC (when picture is saved). The spikes are earthquakes, and harmonic tremor spikes are the “waves” in the harmonic tremor pattern. Copyright of this picture belongs to Instituto Geográfico Nacional.

Update 1:

* When I wrote this blog post. This two earthquakes took place.

1109584 02/11/2011 08:37:11 27.9267 -18.1084 3 1.7 mbLg NW FRONTERA.IHI
1109582 02/11/2011 08:36:00 27.5986 -17.9594 1 1.9 mbLg S EL PINAR.IHI

This are the most shallow earthquakes that I have seen so far. From the depth it is possible a magma has found a clean path to surface in this two areas. Sadly there is no map. So I am not sure where this earthquakes took place in El Hierro volcano.

Update 1b: The earthquake have been revised. Now the depth is 9 km for the ML1.7 and 22km for the ML1.9.

The shallow earthquake.

1109584 02/11/2011 08:37:11 27.9304 -18.1107 9 1.7 mbLg NW FRONTERA.IHI [+]

I am going to post more information when I know more on what is taking place in El Hierro.

Blog post updated at 11:24 UTC on 2 November, 2011