[ACTUEEL] Vulkanen IJsland #18: Verhoogde activiteit bij Bardarbunga

dat hoeft ook (nog) niet ;-)

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Harmonic tremor pulse in Katla volcano

Today there was an harmonic tremor pulse in Katla volcano. I am not sure when this harmonic tremor pulse did start. But I am guessing around 15:22 UTC or maybe around 16:00 UTC. It seems that this harmonic tremor pulse was small, considering the activity in July 2011 in Katla volcano (an minor eruption). This harmonic tremor pulse seems to have happened in the north part of Katla volcano, outside the caldera from my best estimates but might well be inside it in the north part of it.

But its hard to be sure on that detail. From what I can tell, this harmonic tremor pulse does not appear on my geophones clearly. But it might have appeared on Hekla geophone poorly. But it is hard to be sure on that due to wind noise. When this is written the harmonic tremor pulse appears to be dying down. But there is still an possibly that it might pick up again or an new one might start without warning. It is impossible to know for sure how long this is going to stop after this harmonic tremor pulse. This harmonic tremor pulse is due to dike intrusion in Katla volcano at depth, so earthquakes might not happen until it reaches shallower surface in the crust. If the dike intrusion gets that far to start with.

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Series of tremors at Katla
Iceland's huge volcano Katla is stirring into life after tell-tale signs of the potential for an eruption were monitored by observers.

A harmonic tremor has been recorded for two days and small earthquakes have been confirmed at the volcano by the Icelandic Met Office this morning.

It is highly unusual for an eruption in Iceland to occur in the middle of winter but the early indications show Katla is building up power.

Experts are unclear as to whether it is water or magma that is causing this week's sudden increase in activity and the seismic recordings are currently lower than when the volcano first showed signs of a minor eruption last July.

In September, Katla again stirred into life with a harmonic tremor and earthquakes in the volcano's caldera - its magma chamber.

Katla, which has not experienced a significant eruption for 93 years, is the second largest volcano on Iceland and the consequences of a major eruption will be felt across Europe.

In 2010, the country's president Ólafur Grímsson warned "the time for Katla to erupt is coming close, Iceland has prepared and it is high time for European governments and airline authorities all over Europe and the world to start planning for the eventual Katla eruption".

It is believed Katla, named after a vindictive troll of Viking folklore, has the potential to be much stronger and disruptive than the last two Icelandic volcanic eruptions that caused chaos across Europe's air space, grounding flights and closing airports.

Katla is much larger than its neighbouring Eyjafjallajokull – which erupted in 2010 - with a magma chamber about 10 times the size.

Volcanologists warn that if Katla does erupt, the combination of the magma and the large ice sheet covering the volcano could lead to explosive activity and an ash plume for weeks, if not months.

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Harmonic tremor could indicate small eruption
Volcanic tremor (a low frequency vibration often caused by magma rising to the surface) has been observed under Katla volcano in southern Iceland, Jón Frímann reports on his Iceland volcanoes blog (see below), closely following seismic activity in Iceland recorded both by national instruments and his own private geophone network.

According to Jón, there are 2 possible explanations: one could simply be an increase in hydrothermal activity in the northern part of Katla volcano.

The second could be magma movements at depth although there have been no significant earthquakes that usually would accompany an intrusion or small (sub-glacial) eruption, although this still could occur in the near future as often observed in the past during similar episodes of tremor followed by earthquakes.
The last minor eruption at Katla volcano was on 6 September 2011, and caused a small glacial flood.

Op History HD nu het programma: Gates of Hell, waarbij de theorie voorbij komt dat Hekla een toegangspoort zou zijn tot de hel. (Vooral door de vulkanische activiteit, grote geologische diversiteit etc... komt allemaal aan bod)

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Some news has appeared about a sudden warming of the Askja volcano caldera lake. It seems that a melt of ice in the caldera lake started in the beginning of March and by the end of March, the lake was completely ice free.

This is highly unusual and it is not known to have happened before. Such increase in hydrothermal activity is probably caused by a heat source at the bottom of the lake, although so far, there are no other changes visible around Lake Askja. Hydrothermal areas around Askja are active recent reports confirm.

Whether the raised temperature of Askja lake is a precursor to a new eruption in the foreseeable future is speculation at this point.

If you ever frequent Jon Frímann’s blog, you know that he tends to find all the news about potential Icelandic rumblings before pretty much everyone. Well, he seems to have found something interesting going on up in Iceland – a few news reports (in Icelandic) have been talking about the crater lake on Askja caldera has mysteriously become ice-free over the last month while lakes around it (that aren’t on volcanoes) and at lower elevations are still ice covered – not to mention that normally the lake isn’t ice free until June or July. This has lead to a lot of speculation about what exactly is going on at Askja, but thanks its remote location almost in the middle of Iceland, few people have been out there to see what is going on.

A little background on the volcano. Askja is a very complex volcano made up of three calderas. The volcano has mostly erupted basaltic material over its recent history, but it has also had a rhyolitic eruption over 10,000 years ago. Now, usually at a basaltic volcano, the calderas are formed by passive sinking of the land surface, much like we see in Hawai’i. However, at Askja, it appears that the calderas are formed more violently due to explosive eruptions out of the ring fractures bounding the calderas. The youngest caldera formed only 137 years ago (in 1875) and the ~4.5 km diameter feature is home to two crater lakes, Öskjuvatn and Víti. The former is the larger lake, over 200 meters deep, while the latter is a very small, warm crater lake (marked in the photo above near the word “ash?”).

The most recent activity at Askja was in 1961 that produced lava flows near Öskjuvatn – a pattern of eruption that was seen in numerous times since the VEI 5 eruption in 1875. That caldera-forming eruption in 1875 was large enough that ash and tephra fell as far away as Norway and Sweden. Much like the 2010 Eyjafjallajökull eruption, the explosivity of the eruption was likely aided by the meltwater that is readily available at Askja. If you go back to the rhyolite eruption in ~8910 B.C., that ash from that caldera-forming event is found over much of Europe.

After hearing about the melting ice on Askja, I asked Robert Simmon from the NASA Earth Observatory is they had any imagery of the Askja are to see if I could see the melting for myself. Well, as you might guess, trying to image the middle of Iceland in winter from space is, ahem, problematic. However, Robert did find three image that show the lake becoming more-and-more ice-free between February 23 and March 23. The most recent image is at the top and shows Öskjuvatn nearly ice-free. It also shows Víti on the top right of Öskjuvatn and a coating of something on the snow surrounding Víti. {SPECULATION ALERT} Now, it is marked as ash on the image, but there is no confirmation. However, it is hard to come up with any other explanation – some idea might be windblown dust from inside the small warm crater lake or staining from fumaroles that can occur inside Víti. If it were ash, it could be from steam explosions inside Víti that blasted little material out as the water got hot enough to form steam. This discoloration is not visible on the March 6 image (see below), so something new has happened {SPECULATION END}.



n the sequence of three images I tried to mark at least one feature that can be seen in all the images as a reference, but it does seem that the ice had melted on the western side of the lake (starting before February 26) and progressed eastward across Öskjuvatn. Now, why is it melting? What I’ve read suggests that it could be volcanic or meteorologic. The volcano rationale is easy – hot springs and fumaroles at the bottom of the lake are heating the water, causing the ice to melt. The meteorologic involves specific wind patterns that have happened this winter, along with the abnormally warm winter in Iceland. I’m not going to say that either has to be the answer, however, seismicity around Askja has been increasing over the last few years, suggesting magma rising under the volcano, but right now, seismicity is relatively quiet.

Scientists from the Icelandic Meteorological Office and the University of Iceland will be trekking to Askja (Icelandic) this weekend to take measurements and set up instruments to help solve this mystery of the melting ice. In the meantime, the Icelandic government has declared the volcano “off-limits” to tourists on concerns of “the possibility of toxic gases”. Until we have more information, we can only guess what might be going on at Askja right now.

http://en.vedur.is/earthq(...)hquakes/vatnajokull/
Steeds actiever de laatste 24 uur. Ook Jón Frímann heeft er iets over geschreven.

Interesting earthquake activity in Tungnafellsjökull volcano
Posted on April 6, 2012 by Jón Frímann

This is not the most known volcano in Iceland, it also has not erupted in the last 10.000 years at least. Normally this volcano does not have any earthquakes and it remains really quiet. Last major earthquake activity was in the year 1996 in relation to the activity in Bárðarbunga volcano and in Grímsfjall volcano that year. This volcano is named Tungnafellsjökull. It is a small volcano compared to other volcanoes in the area. During the past few days there have been several interesting earthquakes in Tungnafellsjökull volcano. They are small, around ML1.6 the largest ones. But they do have the depth of 10 to 12 km. That is what makes this earthquake activity interesting. Since this suggest that magma might be pushing into the volcano. However at this point in time, there is nothing to suggest an eruption is even close to start there. But with all long dormant volcanoes, nobody never knows what can happen next in them.

The earthquake activity in Tungnafellsjökull volcano. The volcano is located NW of Vatnajökull glacier. Copyright of this picture belongs to Iceland Meteorological Office.

Following the later earthquake today. This activity started on Skrokkalda SIL station. But this might be due to activity in Hamarinn volcano (Loki-Fögrufjöll at GVP). Not Tungnafellsjökull volcano.

The odd tremor activity on Skrokkalda SIL station. I do not yet have any explanation for this activity. Note that Skrokkalda SIL station is on top of a volcano (not on GVP list, but geological maps made in Iceland), named Skrokkalda, it also has not erupted in historical times to my knowledge. Copyright of this picture belongs to Iceland Meteorological Office.

What happens next in Tungnafellsjökull volcano is impossible to know. But it is most likely going to do what it has been doing for the past 10.000 years. A lot of nothing.

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A short update on Askja volcano ice-free lake.

There have been news about the tour of geologist to Askja lake this week in the news. So far the result are puzzling. It turns out that Askja lake is just 1C, but that is normal for this time of year. So why it is ice-free remains a mystery at current time. Data from GPS and seismometers. Samples of the water has been taken also for a analyze and review of weather condition’s is under way. But so far the Askja lake mystery deepens.

Bron: JF

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Earthquakes at Snæfellsjökull volcano
Snæfellsjökull volcano is not often in the news in Iceland. But today there was a short news about it due a study that was done last summer on earthquake activity in Snæfellsjökull volcano. The study was to see if there where any earthquake activity in Snæfellsjökull volcano. The results are really interesting, the main result was there is a lot of earthquake activity in Snæfellsjökull volcano. But also that most of the earthquakes take place on the depth from 9 to 13 km depth. This study was done by Matteo Lupi and Florian Fuchs at Bonn University in Iceland.

The reasons for earthquake activity in Snæfellsjökull volcano is magma. There are not a lot of tectonic movement in Snæfellsjökull volcano area. As it is a volcano zone, but not a rift zone as is the case in most areas of Iceland. But so far it seems that there is no risk of volcano eruption for now. At least that is the opinion for the moment.

Bron: JF

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Earthquake swarm near Hekla
Yesterday there was an interesting swarm of small earthquakes in Hekla volcano system, or to be accurate. The earthquake swarm took place on the edge of Hekla volcano system. How far into the SISZ it was I do not know. For some unknown reasons, the earthquakes have not yet been reviewed. So errors are in there location and depth.

I have no idea what this means in terms of possible eruption in Hekla volcano. But this activity is interesting. But this is however not something that is new to this area. But it is uncommon anyway.

Activity in Hekla volcano system can be monitored on my web page with webicorders. Some of them have high human and wind noise however. As this is not expert setup that I am using.

Bron: JF

ja man... had honger...

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Katla warming up for Eruption

It seems that Katla volcano is warming up for a eruption. As I did mention in last blog post. But there is more to this. As the glacier flood that started on the 28. April 2012 continues according to a email that I got from an geologist working at Iceland Meteorological Office. But that suggests two things. That there is currently an ongoing melting of glacier taking place in Katla volcano, or there is a slow drainage taking place from some area in Mýrdalsjökull glacier. But given increased conductivity following this it is clear that this water has been in contact with magma. But that can be seen with the increased conductivity in the water.

There have not been many earthquakes following this events. But from the earthquakes that have happened. It seems that most likely source for current events is close to or the same area that erupted in July 2011. But at the moment this is just speculation based on limited data. It has not been confirmed so far.



The harmonic tremor that started on 28. April 2012.

This plot shows clearly how the harmonic tremor starts and continues at same level for several days. I do not know if the harmonic tremor is ongoing. But I find it likely, if the small glacier flood is currently going on (that was my last information, but things might have changed during the day). But it is hard for me to know that for sure. But based on latest data from the water monitoring system around Katla volcano, the spike in this glacier flood is most likely over for now. But it impossible to know what happens next in Katla volcano. All that can be done is to wait and see what happens next.

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Op zaterdag 12 mei 2012 14:39 schreef Frutsel het volgende:

[..]

Het was wel lekker rustig buiten zonder de vliegtuigen!

3.4 beving bij de askja. Komt daar niet vaak voor volgens mij.

Het verwarmde meer, en nu ook een flinke aardbeving swarm

Ligt dat niet te ver van Aksja dan? (die swarm dus?)

Minor earthquake swarm close to Herðubreið
Posted on May 15, 2012 by Jón Frímann

Today a small earthquake swarm started just south-west of Herðubreið. But Herðubreið is a volcano cone formation that erupted during last ice-age. But that eruption did break up trough the glacier. Explaining its shape.

The earthquake swarm off Herðubreið. Copyright of this picture belongs to Iceland Meteorological Office.

Largest earthquake so far had the size around ML3.1. But aftershocks have reached the size of ML2.5 according to IMO automatic magnitude estimate. This earthquake swarm is currently ongoing.

Katla volcano (Iceland): earthquake swarm under icecap
A new swarm of earthquakes has started Tuesday (5 June) evening at Katla volcano. Until now, 34 quakes up to magnitude 2 have been recorded beneath the volcano, at mostly shallow depths around 3-7 km. The quakes are clustered in the SE part of the caldera, and could indicate that a magmatic intrusion is taking place in this area. Whether this is a precursor to a possible eruption of the volcano remains speculation. [/q]


Earthquake swarm at Katla volcano on 5-7 June 2012 (Icelandic Met Office)

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Update Sat 09 Jun 12:20
The earthquake swarm under the southern part of the icecap of Katla volcano that had started on 5 June continues with 30 more quakes recorded during the past 48 hours.
The quakes are mostly very small, but a few were between magnitude 2 and 3, and most are located at shallow depths of less than 5 km.

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Op woensdag 13 juni 2012 00:02 schreef lipjes het volgende:
nu dus

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