This will be short, and I will update it soon. The research airplane TF-SIF has sighted four sigkatlar over Bárðarbunga, the characteristic depression in the ice sheet caused by the extensive melt of inflowing magma into the glacier. News will be coming fast, so expect updates and corrections as they arise!
Welcome to a special breaking edition of Eldfjallavakt!
An eruption is considered to have begun
A sigkatla (depression in an ice sheet caused by the volcanic melting of the ice underneath it) has formed southeast of Bárðarbungaa and it is considered that an eruption has begin or had happened. This is according to the Met Office. The scientific committee of the public protection services is now having a meeting with the scientists of the Met Office and the Earth Sciences center of the University of Iceland.
The public protection department of the state police says in an announcement which was sent out now at 11:00 that they still haven't been able to confirm that an eruption has begun, or had begun, in the northwestern side of Vatnajökull.
Two sigkatlar have formed south of Bárðarbunga's caldera, which is not possible to explain in any way other than that magma has melted the glacier, according to information from the Met Office.
TF-SIF, a coast guard airplane, flew over Vatnajökull today and saw the sign of two sigkatlar. The coordination center has been activated and scientists are meeting now about the situation,.
They saw land subsidence in a crevice which leads to Askja.
Víðir Reynisson, the department head of public protection, said in a conversation with RÚV this evening that more information will not be available until late this evening. When asked whether an eruption has begin Víðir said that it is difficult to say before that.
"If these are rapid changes that it's difficult to see any other explanation than that this is an eruption, but these are very difficult situations this evening. This was not there on saturday at the very least," says Víðir, who is attending the meeting with the scientists of the Met Office and Earth Sciences department of the University of Iceland.
When asked he says that there have not been any changes on the river Jökulsá á Fjöllum.
Link. Let's just post that which wasn't in the other article.
In the plane they saw shallow sigkatlar and rifts 4-6 kilometers long to the southeast of Bárðarbunga. There is 400-600 meter thick ice in the area. The region is in the watershed of the river Jökulsá á Fjöllum and Grímsvötn.
...
There is no sign of eruption tremors.
Oh, and the article said that the sigkatla rifts are 10-15 meters deep.
My read thusfar: this didn't happen just now, it started in the earlier quakes, we're only seeing it now. Position: Bad. This is rather deep , rather thick ice. It should be able to build up a rather big jökulhlaup there, I would think. :(
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Sigurlaug said in the news on radio RÚV that the sigkatlar have not subsided all that much. They were 10-15 meters deep but the claier in this region is 400-600 meters thick. The implications of the melting would be most likely an eruption or geothermal activity. It should soon become clear.
There still has been no water observed under the glacier but Sigurlaug says that it could have run into Grímsvötn (Ed: subglacial volcanic lakes from another volcano). It still is possible to wait for data to confirm whether the height of the ice slab has changed, that is whether the height over Grímsvötn has become elevated.
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Víðir says that the depressions are 4-6 kilometers length and that they'll have the plane fly over them immediately once it gets bright out tomorrow to assess the situation again. They're currently re-analyzing the numbers from the meters of the Met Office to assess whether they overlooked an event.
"The quake activity is so ridiculous that it hides so much in the noise."
Víðir said that the public protective services of the police consider that they have good time to assess whether to evacuate the adjacent region.
"We think that there will be sufficient time because of how good devices we have for monitoring," said Víðir and then ran back into the meeting.
And here we see a stupid tourist trying to make us pay to recover his body. :Þ
Meanwhile, the dike keeps advancing toward Askja, and it's looking bad:
Eruption likely in Askja if the dike reaches there
There is a great likelihood that the dike under Vatnajökull will enter Askja, says Icelandic geology professor in London. If it enters the magma chamber than there will likely be an eruption.
Ágúst Guðmundsson, professor of the geosciences department of Royal Holloway College, has among others researched dikes and volcanic activity in Vatnajökull.
"The probability is now that, and I stress as the situation is at present, that there's a big probability that this dike will enter Askja. And given the size of the dike, i it enters the small magma chamber of Askja then there's a large likelihood that it will be at least breakage and probably an eruption."
He says that the dike under the glacier has gotten very long, 42 to 43 kilomters, and that the magma which has gone into the dike is at least one to two cubic kilometers (Ed: stop, take a breath...). He was interviewed in Fréttablaðið this morning.
"It's also good to note that most dikes in the world, whether in volcanic systems or outside them, never reach the surface. That is to say in most possible eruptions, eruptions that are thusly in the pipeline they never erupt."
Magnús Tumi Guðmundsson, professor of geophysics, says the dike has now gotten to 10 kilometers from the central Askja volcanic system itself and doesn't have long to go to reach an eruption vent which occurred in the third decade of last century and which streches south from Þorvaldsfall. This dike comes out of the central volcanic system of Bárðarbunga and Ágúst says that if it keeps going than in short order it could become major:
"This is the first time, if it goes into Askja, then it will be the first time that we are seeing a primary conduit actually travel from one volcanic system over into a different one. And that can be said, with no ambiguity, dangerous.
(singing) "That's great, it starts with an earthquake, birds and snakes and aeroplanes..."
Oh, and it's rifting outside the glacier too, lovely! This is from Páll Einarsson, probably the most optimistic of the scientists involved in this study so far, the guy who said just yesterday that it's going to die out in a couple days:
Clearly rifting is visible on the surface of Holuhraun, north of Dyngjujökull, because of the dike which has been ripping itself a path deep under the earth. Geologists saw the rifts today, in monitoring with TF-SIF, an aircraft o the coast guard.
In these pictures which were taken today one can see clearly new rifts, both in a tuff ridge in Holuhraun and also in the lava itself, northeast of the ridge. The large rifts in the middle of the ridge are old, says, Páll Einarsson, professor of geophysics at the Earth Sciences center at the University of Iceland, but clearly it's moved around. "The smaller ones in the ridge and Holuhraun are clearly new," says Páll.
"This doesn't necessarily mean that the magma is on its way up to the surface," says Páll. "But that is however of all likelihood the place where the spreading is most in the strata below, where the dike is pushing northeast, and the indications on the surface bear witness to what is going on underneath."
Páll says that such things have been seen before in connection with magma flows underground, for example, in the Krafla Fires (Ed: I just knew he'd bring up Krafla! ;) ). "Especially we saw these in te magma lows which flowed the furthest out rom Krafla, all the way to Kelduhverfi. There one could see rifts in the settlement, but magma did not however come up to the surface in that case, thus seeing these signs doesn't mean that a volcanic breakout is threatening."
In the picture below one can see Holuhraun. The new rifts are visible halfway to the tuff ridge and northeast of it.
Finally, a map!
Rather than translating this article, I'll paraphrase:
Víðir: We don't know what's going on! Somebody please tell us! (okay, he didn't say that in exactly those words, but...)
Páll: Nothing has happened that says an eruption is going on.
Sigurlaug: Clearly there's melting, it's got to be either an eruption or a huge amount of geothermal activity. But who knows whether the water will even come out?
Magnús: If it went south into Grímsvötn then it could take many hours before we see any potential jökulhlaup to the south.
Víður: Why are all of these sigkatlar to the south of where we expected? And really, what else could it be other than an eruption that caused this?
Update, 1:30 28 august: Final update for the night, unless something else crazy happens before I go to sleep. I think the rate of substantial news updates has slowed, so let's try to sum up everything that we've seen.
1) 4-6 kilometers of sigkatlar that are 10-15 meters deep have formed on the southeast side of Bárðarbunga's caldera, heading off into the direction of the dike (a little south of where one would expect), under 400-600 meters of ice.
2) There's not yet been any signs of a jökulhlaup (glacial outburst flood), and right now people can only guess as to where the water is going. People are speculating on north, south, and simply collecting in Grímsvötn. Strangely nobody has mentioned the possibility of west, so I'm certainly hoping that's improbable, as that's where most of our electricity comes from (although the reservoirs can soak up small to moderate sized jökulhlaups, just nothing too major).
3) There's no clear data for an eruptive event. But since the ground won't freaking stop shaking for a minute so they can get a clear reading, that's understandable. That said, there's no clear picture of what exactly has happened here - an eruption appears simply to be most probable scenario.
4) The dike continues its slow march to the north. Despite its depth (5-10+km), the pressure it has put on the surface has been sufficient to make new rifts on the surface.
5) The dike has gotten close enought to Askja that it is now interacting with Askja's own stress field and causing quakes. It is now considered likely that it will intersect with Askja's caldera, and that the outcome will be an eruption of Askja.
Let's talk about this for a moment. There's one question that's on everybody's mind here:
What On Earth Is Going On Here???
The predominant theory thusfar has been that the slow rise in pressure Bárðarbunga's caldera led to a rifting event and the formation of a dike, which has been following the preexisting rift zones driven forward primarily by magma from Bárðarbunga's magma chamber. As this happened, pressure dropped in Bárðarbunga's caldera, triggering an ongoing series of massive quakes in the caldera as the ground over the caldera subsided.
Okay. Except that there's an entirely different explanation at hand here which fits the data better. Enter two of the scientists on the team analyzing the situation, Haraldur Sigurðsson and Ágúst Guðmundsson. But first, a graph to show what we're going to talk about.
The top graph is what had been assumed, by and large, to be happening here. Those of you reading my diaries may have seen this referred to by some scientists (especially Páll) as being a repeat of the Krafla Fires. These were a nearly decade long event of low-intensity lava fountains, a nice tourist eruption. This would be a good situation.
Except, not so says Ágúst (remember, this was written before the signs of eruption came clear):
Lengthening about four kilometers per day
The earthquake storm in Vatnajökull and advance of the dike under the glacier to the northwest (Ed: northeast?) is one of the most remarkable earth sciences events that scientists and the general public in Iceland have ever witnessed. Never before has anything similar been recorded with modern equipment.
This is the view of Ágúst Guðmundsson, a professor at the Earth Sciences department at Royal Holloway, about the course of events over the previous days in Vatnajökull, and he has decades of experience among other things investigating dikes and in particular those in the older rocks in Iceland.
"This is an extremely powerful event and will cast light on the power behind the process of the land coming apart in this region. Underneath the glacier there is considered to be a mantle hot spot, and nowhere in Iceland is there more magma underneath“ says Ágúst and points out that the tremors are in a huge region where the largest eruptions in the history of Iceland have occurred. He says that a large eruption is possible, although a small eruption or that the quakes would die out is much liklier.
In the roots of the earth
Ágúst says that the dike is very large; the so-called main conduit which forms outside of the primary volcanic system. Some have roots that reach down to the magma chamber under the volcanic system but that's not the case with the dike which has now crawled forward an average of four kilometers a day in the past ten days. "This is coming from much deeper, or out of the deep magma reservoir which lies underneath at 15 to 20 kilometers deep, similar to what is under most volcanic systems in Iceland. Similar reservoirs are much larger than a magma chamber. The dike is so large that it controls the entire stress field, or energy, of this region. There is so much pressure in it that it has an effect on the volcanic systems around it." says Ágúst, and adds that the most remarkable thing with the situation is that in an instant there comes clear movement in the direction of the central volcanic system of Askja/Dyngjufjöll.
"If the dike continues forward at several kilometers in the same direction, which we don't know whether it'll do, then the stress field of the dike will met the stress field of Askja, the volcanic system itself and the magma chamber underneath, which has an effect reaching out several kilometers from itself. So the question is whether the dike goes under Askja itself," says Ágúst who considers that there's way too much magma already in the dike that it could have come from the central Bárðarbunga system. It's logical that it's coming up from a magma reservoir at a greater depth where there's many times more heat and magma collects. He considers though that by far most dikes, wherever one finds them in the world, never reach the surface.
"But the key factor is that when the tip of the dike reaches 8 kilometers from the caldera itself, which is as as wide as the caldera is, then the dike will begin to feel the tension field there, which can lead to it running into the magma chamber under Askja," says Ágúst who admits that this could cause an eruption in the historically famous volcano.
Nothing like Krafla
The probability of the chain of events in the Krafla Fires from the beginning in 1975 has been raised in the past several days. Ágúst however argues that something different is involved here.
"I see nothing that suggests that something similar is happening, and consider this a totally different event. In Krafla the consensus was that magma had come up into a small chamber, and then continued forward in small dikes out of the Krafla chamber to the north and south. There I consider that the dike itself is what governs the process, not the magma chamber, which could be the primary difference between these two," says Ágúst.
Data from scientists from yesterday show that quake activity is still very great. Most activity is at the end of the dike north of Dyngjujökull, which has now reached 10 kilometers from the end of the glacier.
The dike under Dyngjujökull is now considered to be 40 kilometers long. The likely estimation, basedon GPS measurements, suggests that the volumetric increase just in the past day is about 50 million cubic meters. This quantity is over 500 cubic meters per second or over 1.5 times the average flow of the river Ölfusá, to put the size in context.
Ágúst considers rather that much more magma is in the dike than 350 million cubic meters, as the calculation here suggest. Even threefold more, which equals all the magma that came up in the Surtsey eruption from 1963 to 1967 and the Hekla eruption of 1947, put together. Finally it's right to reiterate as Ágúst reminds us, as with other scientists here, that the different possiblities which are being raised are not all of equal probability but we can't write off any of them.
That is, Ágúst considers the primary driver of this whole sitution the extremely large deep magma reservoir, not Bárðarbunga's (still extremely large, but much smaller) magma chamber. Bárðarbunga would be a symptom rather than the cause.
Daily Kos reader ypochris, thus, raised a good question when I brought up Ágúst's argument:
I don't understand the apparent Bárðarbunga caldera collapse and resultant strong earthquakes there - unless it is increasing pressure, rather than decreasing, that is causing the movement. But I'm sure tilt meters and GPS stations would detect any inflation. As they, no doubt, are the basis for assuming deflation. So a substantial amount of magma seems to have moved out of the Bárðarbunga kvikuhólf.
Enter Haraldur. Because he things we need to completely invert what we're thinking about what's going on in the caldera: that it's not
deflating and collapsing, but rather that it's
overinflating and pushing a massive plug of rock out from underneath it:
This morning there was the largest eruption in Bárðarbunga thusfar. It was 5.7 magnitude and 6.2 kilometers deep. It is positioned deep under the northern ridge of the Bárðarbunga caldera, according to the Met Office. Notice that that a quake of magnitude 5 is precisely 33 times stronger than a quake of magnitude 4. This major quake is of the same magnitude as the ten quakes under Bárðarbunga which Meredith Nettles and Göran Ekstrom researched in an article from 1998. They were quakes from 1976 to 1996, which they analyzed, at depths down to 6.7 kilometers. What is it, which sets in motion such major quakes under the volcano? What does it mean for the future?
Experts have indicated that they consider the quake this morning a consequence of magma flow out of the magma chamber under the caldera and into the dike. That is to say the roof o the magma chamber, which is subsiding and the quake would be on the edge. According to their interpretation the magma chamber extends down to 6.2 kilometers depth.
Magma chambers under Icelandic volcanoes which have calderas are rather shallow under the surface. It is considered that the magma chamber is 2-3 kilometers deep under Krafla, 2 kilometers under Katla, and 3 kilometers under Askja. A magma chamber 6 kilometers deep under Bárðarbunga would be very different from those we're familiar with. Thus we should consider the other possibility that the large quakes are of a type which Ekstrom suggests: connected to the motion of a round rift, which is in the crust UNDER the magma chamber. I have discussed this possibility of Ekstrom's before here (links) and also here (links)
Seismologsts have yet to determine what kind of quakes these are, out from "first motion" or study of the motion of the first waves of the quakes. But meanwhile we should consider that these are in accordance with the theory of Ekstrom. If subsidence is occurring in the caldera and causing quakes then that should be seen in the GPS meter in Dyngjuháls. But it's not. Thus one suspects that the cause of these powerful quakes is other than caldera subsidence
Let's clarify, using pictures. Here's the remarkable Richat structure in Mauritania:
What on earth is that thing? It's believed to be a volcanic dome which has been sheered off. So why the rings? Well, what's now believed is that the floor of its magma chamber was a conical plug:
When pressure grew too much in the chamber, it would push the plug downward. This opened up space between the walls of the plug and the surrounding rock, which filled with magma. This hardened and became the next point of failure for the next expansion event, thus laying down rings one after the next.
Haraldur presents evidence that suggests that many of the larger Icelandic volcanoes such as Bárðarbunga follow the same pattern. That would be, rather than requiring that the magma chamber be over six kilometers deep, it's the plug underneath the magma chamber that is so deep. And as for the magnitude, it's fracturing a larger amount of rock at higher pressures in order for the plug to slide downward.
So what if Haraldur and Ágúst are right? Well, that's not a very pretty situation. Because that means that this incredible flow rate is coming straight from the most massive source of magma in Iceland, the deep reservoirs near Bárðarbunga - and that Bárðarbunga is highly pressurized, rather than being drained.
Combine this with the dike interacting with Askja's stress field. How much worse of a situation could you ask for?
Let's hope that they're very, very wrong. Or that if they're right, all of these forces that are in motion stay the heck down there.
