Category: Harmonic tremors

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Special report: Update 6 on the eruption in El Hierro, Canary Islands, Spain

Special note: Please notice that my (personal) watching system is also going to include the mainland of Spain (mainland Spain has two volcanoes that I am aware of, along with some earthquake activity) when I change it next month, along with Canary Islands. Everything else is also going to be a subject to a special reports if the event is important enough. That is not always going to be case however. But I am going to post more details on this in the beginning of next month.
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Little seems to have changed in the eruption of El Hierro since my last update on it. That was on 19 October, 2011. Harmonic tremor is constant, but appears to have dropped a little in the past few days. But with the fluctuation that is often increases again before it drops down again. This means that the eruption is ongoing, but is loosing power to continue at current eruption vent. This was not unexpected. This has however not slowed down inflation in El Hierro from what I can gather on GPS data on El Hierro.

As the current eruption vents close down it seems that earthquakes have started again under El Hierro. But the earthquakes have the depth from 28 km and up to around 5 km. This strongly suggests that new magma is entering under El Hierro and is again increasing the pressure inside the El Hierro magma sill (or chamber, but note that El Hierro does not have a stable magma chamber it seems). This increases earthquakes while the magma does not have any good path up to the surface. When a new path for the magma starts to form again, a large earthquake swarm is going to take place in El Hierro. It is not going to be anything bigger then already has taken place in El Hierro already. With the largest earthquakes going up to Mb5.0 in size. That is at least my opinion.


All the earthquakes that have happened in El Hierro since magma intrusions started in July 2011. This pictures clearly shows in my view the amount of magma (in terms of size, not volume) that is under El Hierro at the moment. As it is marked on the outer layers by the earthquakes. Copyright of this picture belongs to Instituto Geográfico Nacional.


The harmonic tremor in El Hierro at midnight on 21 October, 2011. As can be seen, it fluctuates a little bit. Copyright of this picture belongs to Instituto Geográfico Nacional.

The major risk in the current eruption cycle of El Hierro is the risk that new eruption vent is going to open up nearby a human population without warning. But El Hierro has a lot of cinder cones from earlier eruption cycles. That creates the risk that a new eruption vent is going to open up on dry land without warning. But it is impossible to know when and where that might happen.

Claims that this eruption in El Hierro is going to create tsunami due to landslides are false and have no basic in fact or reality. As landslides are unlikely to happen in this eruption episode or if a eruption happens on dry land.

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Possible harmonic tremor spike in Katla volcano (it might just be the weather)

With all the bad weather in Iceland during the past few days it is hard to be sure on this. But it seems that a harmonic tremor spike is about to start in Katla volcano. So far this spike is rather small from what I can tell at the moment. At the moment it is impossible to know how this develops, if this is a harmonic tremor spike to begin with in Katla volcano.


Current earthquake activity in Katla volcano. Copyright of this picture belongs to Iceland Met Office.


Current tremor levels in Katla volcano. The harmonic tremor spike can be seen at the end of this plot. Copyright of this picture belongs to Iceland Met Office.


The possible harmonic tremor spike in Katla volcano. Copyright of this picture belongs to Iceland Met Office.


The possible harmonic tremor spike in Katla volcano. Copyright of this picture belongs to Iceland Met Office.

This might just be bad weather. It is hard to know at the moment. But currently the weather is decent. But there is a new storm coming over Iceland in the next 12 hours or so, at least that is the weather forecast now from what I can gather.

In September over 480 earthquakes where recorded in Katla volcano caldera. But this is the most earthquake activity since at least the year 1999. The largest earthquake in September in Katla volcano was a ML3.4 with the depth of 5.2 km.

More the earthquake activity in Iceland during the month of September.

Jarðskjálftayfirlit í september 2011 (Vedur.is, Icelandic, Picture)

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Special report: Update 5 on El Hierro eruption, Canary Islands, Spain

This is a special report on the eruption in El Hierro, Canary Islands, Spain.
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From the harmonic tremor data during the current eruption in El Hierro. It seems that the eruption has dropped in strength during the past 48 hours or so. But that most likely means that the current eruption crater is closing up. But this does not mean that the eruption is over, as new fissures might open up without any warning close the El Hierro Island or on the island it self. It is impossible to know that for sure at this moment. As it currently stands it is unlikely that a new Island is going to form offshore of El Hierro island, as the current eruption crater does not seem to have the energy to break the surface of the ocean. Earthquake activity in El Hierro volcano remains about the same as it has since the eruption did start on 10 October, 2011.


Harmonic tremor in El Hierro volcano at 18 October, 2011 at 23:26 UTC. Copyright of this picture belongs to Instituto Geográfico Nacional.

For the moment, the only thing that can be done is to wait and see what happens next. But it is clear that the eruption in El Hierro is far from over from the data that I have seen so far. But this eruption might pause for days to weeks, as that is not uncommon thing for a volcano to do during a active eruption cycle.

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Special report: Update 4 on the eruption in El Hierro, Canary Islands, Spain

Short note on comments: During the eruption in El Hierro there has been a lot of comments on this blog. Over the past 4 days (or so) there have been about ~1500 comments. If your comments is held for moderation, the blog says so. Do not try to repost your comment if that is the case. As the second comment is just going to be held in moderation as the earlier one. It takes me a little while to approve the comment and to make it appear. If your comments disappears and cannot be seen, the spam filter has eaten it. It also takes me a while to check the spam filter and restore comments that have gone there. Please do not just post comment with nothing but links, that increases the risk that the comment is going to be eaten by the spam filter.
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Short note: Please note that I am not a expert in the field of volcanism, volcanoes and earthquakes. I never claim to be one. Regardless if I am asked or not. I am a man with interest in this field. I read a lot of books and studies on volcanoes and earthquakes. But that does not make me a expert in this field. If you want to speak with a expert, go and find one. Because I am not it.

Now. About the eruption in El Hierro volcano in Canary Islands. This is going to be a short blog post about the eruption.

From what I can tell and the information that I have seen. At least two more vents have opened up on the from what I can gather on the pictures and the reports from Canary Islands. So far all the new vents are under the ocean and at depth of no less then 150 meters. So seeing them directly is quite hard for the moment. There are continues deep earthquakes under El Hierro volcano, but that suggests that new magma is flowing into El Hierro volcano.

During the weekend floating magma bombs where (or some type of magma, I do not have the exact word for it in English at the moment) floating on the ocean. But this means that at least one of the vents that started erupting in the beginning is getting close to break the surface of the ocean. If the eruption continues in that vent for a little while longer. If it gets above the surface of the ocean, it is going to form a island and a lava eruption is going to start once the ocean cannot get any more into the crater.


The harmonic tremor of the eruption in El Hierro volcano today (16 October, 2011) at 22:35 UTC. Copyright of this picture belongs to Instituto Geográfico Nacional.

There is a risk of new fissures in El Hierro opening up without warning. From what I am estimating, the area that this can happen has expanded about ~5 km or so from my original estimate that I made in few blog posts ago. The risk of new fissure opening up on land is going to remain high while this eruption is taking place. But this might well be a period of eruption activity for El Hierro. It is impossible to know for how long it is going to last, it could be weeks or it could be months and up to years of activity.

I am going to post more information on El Hierro when I know more tomorrow. I am also going to write about the earthquake activity in Hengill volcano tomorrow if I have time to do so.

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Special report: Update 3 on El Hierro eruption in Canary Islands, Spain

I am going to fully integrate Canary Islands into my watch volcano monitoring system in the beginning of next month, but Canary Island won’t be part of my emergency system until I move to Canary Island (that is because of technical reasons mostly). When that happens, blog post regarding earthquake and volcano activity won’t be a special report. Just a normal blog post as with Icelandic volcanoes. I am doing this as I plan on moving to Canary Islands in about 10 years time (+- maybe few years depending on how my plans work out). A name change on this blog is planned in the beginning of the year 2012. But it takes a while for me to think up a new name for this blog.
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The eruption in El Hierro volcano continues at the same phase as before. With little change so far. Currently the eruption seems to be in two vents, as it did when it started on Monday. There have been unconfirmed reports of new vents opening up closer to the coastline. But given lack of direct evidence that should be there. I do not believe that a new vents have opened up closer to the coastline so far.

Deep earthquake continue in El Hierro volcano. But that means a new magma is coming in from the mantle and is flowing upwards into the volcano. For long as deep earthquakes are being recorded the eruption is going to continue. It is impossible to know for how long this inflow of magma from the mantle is going to continue. But this means that the eruption is going to continue for time being. With the risk that new vents might open up at any time on and around El Hierro volcano. This inflow of new magma has also been confirmed by GPS measurements on El Hierro volcano (the island). But since the eruption did start, no major change has been seen on the GPS real time data.


The harmonic tremor in El Hierro volcano yesterday. Copyright of this picture belongs to Instituto Geográfico Nacional.


The harmonic tremor in El Hierro volcano today (until 21:20 UTC about). As can be seen by comparing the pictures between today and yesterday. Not much has changed since yesterday in terms or harmonic tremor. Copyright of this picture belongs to Instituto Geográfico Nacional.

If a eruption vents open up on a land. The following eruption is going to be lava only. No volcano ash and no explosions as El Hierro is a shield volcano like the one on Hawaii and that means only lava eruptions. If a eruption vents opens up on the shallow coastline, there are going to be explosions for as long the ocean water can get into the crater. The moment it closes up the explosions stop and lava eruptions starts.

Please note that I am on slow internet connection (3G). So I am not going to post anything if the internet connection is really slow, as sometimes seems to happen. I am going to try and solve this issue by using my 3G phone and connect that way. At least I am going to try and see what happens.

Blog post updated at 03:20 UTC on the 15 October, 2011.

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Special Report: Update 2 on the eruption in El Hierro

This is a special report on the eruption in El Hierro. This is also a good time (as any) to announce that I plan to write about volcanoes in Canary Islands in the future. As I plan on moving to the Canary Islands in about 10 years time (no reason to start late on this). But I have already induced the Canary Islands volcanoes into my personal watch system. But I have my own personal system to watch volcanoes in Iceland and now Canary Islands. However, Canary Islands are not part of my personal emergency system until I move to Canary Islands.

Update to the name of this blog is going to happen soon, but I am not sure when. But I am going to move in a about 10 years time (going to live in Denmark until that happens). Until then, they are going to go into special report group and only major events are going to be blogged about. Please note that this might change if I move earlier to Canary Islands then I now plan.

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The eruption in El Hierro volcano continues today, as it did yesterday. But the strength of the eruption appears to have dropped today from what it was yesterday. But this does not mean that the eruption is over. It just means that the current fissure that is erupting is about to close up, mostly due to the material that it has been ejecting into the ocean floor. That means a new fissure or vents is about to open up somewhere. When and where is impossible to know. But this is the nature of volcanoes that erupt in this manner, but El Hierro is a shield volcano [second link here]. Good examples are Krafla volcano and Vestmannaeyjar Island volcano. Both of those volcanoes are in Iceland.

Today around 14:20 UTC there was a sharp tremor drop in El Hierro. This means that the magma flow dropped in the current eruption fissure. This also means that if the pressure is not enough that fissure is going to stop erupting. Because of this has happened a new fissure or a vent should be expect at any time as I have told before. When and where that might happen is impossible to know, as that outcome depends on where the magma finds its pathways inside the volcano. There might not be any earthquakes before this happens, as the rock is unlikey to be hard enough to make them. Some small earthquakes might happen if the rock layer is hard enough. Today few deep earthquakes have been recorded. This means that new magma is getting into El Hierro volcano from the mantle (where no earthquakes happen). This also means that this eruption might take place for some time now. But it is impossible to know for how long, as there might be a lot of magma flowing up from the mantle it self and up to El Hierro volcano.


The harmonic tremor and the drop in the harmonic tremor today. Copyright of this picture belongs to Instituto Geográfico Nacional.

Many people have been wondering why this eruption has not been seen. The fact is that depth drops quiet fast around El Hierro Island. Around 4 km out the depth is close to 1.5 to 2 km, it is only close to the island that the depth starts to get shallower. At the moment is is hard to say what happens next in this eruption on El Hierro. But more vents should be expect to open up then have already have.

I am going to update this blog post if anything changes in El Hierro volcano eruption.

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Special report: Eruption at El Hierro volcano, Canary Islands

At 04:18 UTC on 10 October, 2011 a eruption did start somewhere close to the El Hierro volcano Island (but inside El Hierro volcano system). So far nothing has been seen to this eruption, so location is uncertain at the moment. At the moment this eruption has only been confirmed by harmonic tremors seen on seismometers on El Hierro island.

From what I can tell, based on the harmonic tremor plots. It seems that the eruption has been growing in size since it started well over 12 hours ago. This suggests that the eruption is growing in size. That also brings up the issue that new fissures might open, both into deeper ocean and on shallower depth and even on land without any warning at all.


The harmonic tremor from El Hierro at 21:08 UTC on 10 October, 2011. Copyright of this picture belongs to Instituto Geográfico Nacional.

A location for the eruption has been suggested, as can be see on this map here.


The speculated eruption in El Hierro. Copyright of this picture belongs to el-mundo.es Thanks to Dr. John v. Kampen for this map via email.

Lack of earthquakes does not mean that magma is not the move and has not reached the surface already. But this however suggests that magma now has a free flow upwards to the surface since sometimes yesterday, when the earthquake activity did drop suddenly from ~100 earthquakes to ~30 earthquakes over the day.


Current earthquake activity in El Hierro. It is my personal opinion that the eruption is around -18.05 and 27.65 to 27.70 (middle of that area, around 450 meter depth). Copyright of this picture belongs to Instituto Geográfico Nacional.


Spectral image of the harmonic tremor. This image clearly shows that the orgin of the harmonic tremor is magma on the move. Not something else. Copyright of this picture belongs to Instituto Geográfico Nacional.

I am going to update this blog post as more is known about the eruption in El Hierro.

Canary Island news about this. With thanks to Dr. John v. Kampen how did send them to me in a email.

Posible erupción al sur de El Hierro (Youtube, Spanish, Video)
¿Emergerá una nueva isla? (Youtube, Spanish, Video)

Blog post updated at 21:49 UTC on 10 October 2011.

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Tremor pulses in Hamarinn volcano (most likely)

During the past two weeks there have been tremor pulses in Hamarinn volcano (is claimed to be part of Bárðarbunga volcano system), at least most likely that volcano. But it might also be a volcano that I call Skrokkalda Volcano (other name might be Hágöngur volcano) (it has no entry on GVP web page, I do not know why). But given recent history I find it unlikely to be the case.

This harmonic tremors might be due to dike intrusions. I find it unlikely to be from a man made lake called Hágöngulón that is in this area. The harmonic tremor pulses look like sharp spikes on the tremor plot on the Skrokkalda SIL station.


Harmonic tremor spikes from Hamarinn volcano. Copyright of this picture belongs to Iceland Met Office.

This pattern of harmonic tremor spikes was seen all last year and all of the year 2009 from what I can remember. I do not have tremor charts from that period. But however this suggests that more magma has now started to flow into Hamarinn volcano. But there was a small volcano eruption (it seems so, given the flood that took place in July) in Hamarinn volcano last summer (summer 2011). What happens next is a good question.

This process of inflow of magma seems to without earthquakes, or close to it. I do not know why that is and I have no ideas that explain it.

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Update on Katla volcano earthquake swarm

There has not a lot changed in the past few hours since the earthquake swarm did start in Katla volcano. Eruption has not yet started in Katla volcano and when it might start is still a mistery.

Current map of the earthquake activity.


Current earthquake activity in Katla volcano. Copyright of this picture belongs to Iceland Met Office.

Here are traces from my Heklubyggð geophone. But that is currently the geophone that I have that is closest to Katla volcano. I am collecting donations so I can buy two new geophones. The blog post about that can be found here. I do not expect to have the geophone in place before a eruption starts in Katla volcano this time around. So far the donations are up too 5,410.74 DKK, so I am not far from what I need to collect. I do not have to pay customs of this according to a email I got from the customs office when I did ask about it. But I have too pay 25,5% VAT on this when it gets here. That might be a good amount I think in Icelandic Kronas (ISK).


One of the large earthquakes. This is not the strongest earthquake in the earthquake swarm that took place this morning in Katla volcano. This is also a double earthquake, that is two earthquakes taking place at the almost the same time. That is the reason for the odd looking wave form on this earthquake trace. This picture is released under Creative Commons licence. See Licence web page for more details.


A ML3.0 earthquake that took place in Katla volcano this morning. This picture is released under Creative Commons licence. See Licence web page for more details.


The largest earthquake in the earthquake swarm this morning. Its size was ML3.55 with the depth just short of 1 km. This picture is released under Creative Commons licence. See Licence web page for more details.


A ML2.94 earthquake in Katla volcano this morning. This picture is released under Creative Commons licence. See Licence web page for more details.

So far it has quieted down in Katla volcano. But that does not mean a lot. As magma can go on the move at any time. Without any warning at all. So monitoring Katla volcano is important with that fact in mind. According to Iceland Met Office, this is the largest earthquake swarm in Katla volcano caldera since the year 2002.

I am expecting more strong earthquakes to take place in Katla volcano. But it is impossible to know when a new earthquake swarm might start in Katla volcano and how large and long it is going to last. For the moment, it is just wait and see.

Iceland Met Office has put up a news about this in English. Thanks too the readers how pointed this out!

Earthquake activity in Katla volcano October 2011

Icelandic News about this earthquake swarm.

Snarpasta hrinan í Kötlu frá 2002 (Rúv.is, Icelandic)
Snörp hrina í Mýrdalsjökli í nótt (Rúv.is, Icelandic)
Snörp hrina í Kötlu (Vísir.is, Icelandic)
Sterkir skjálftar undir Mýrdalsjökli (mbl.is, Icelandic)
Um 20 skjálftar yfir 2 stig (mbl.is, Icelandic)

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What did happen in Hamarinn volcano yesterday

I really did think that a eruption was about to start in Hamarinn volcano yesterday. As the signal that I was seeing was not far from what I did see on 12 July, 2011 when a eruption did take place for sure in Hamarinn volcano.

Here is the tremor signal from 12 July early in the morning.


The harmonic tremor signal on 12 July, 2011 at 07:49 UTC. Copyright of this picture belongs to Iceland Met Office.

Here is the signal on the 27 September, 2011.


The harmonic tremor signal on 27 September, 2011 at 09:34 UTC. Copyright of this picture belongs to Iceland Met Office.

The tremor signal in July was stronger, but it looks almost the same way as the signal yesterday (27 September, 2011) did. So I think I know what did happen yesterday (27 September, 2011) in Hamarinn volcano. There might have been a minor dike intrusion into Hamarinn volcano. There where no earthquakes as it might have been going up resistance free pathway. But it is hard to know that for sure at the moment. Later events might however make what happened yesterday more clear what did happen on 27 September, 2011.

Note: I am looking for data on El Hierro volcano. As I am going to make a special blog post about it soon. I am looking for everything that I can get my hands on and might be useful to me.

Note 2: I have updated this blog post here and added the most recent eruptions in Iceland. Blog post: A short history of volcano eruptions in Iceland

Blog post updated at 12:59 UTC on 28 September, 2011.