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Iceland Magazine @IcelandMag 41m
Breaking news! The ice cap above the #Bárðarbunga volcanic system is opening up. Is this an eruption?
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.
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.
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."
A rift zone is a feature of some volcanoes, especially the shield volcanoes of Hawaii, in which a linear series of fissures in the volcanic edifice allows lava to be erupted from the volcano's flank instead of from its summit
What happens in a phreatomagmatic eruption is usually the erupting magma is directly introduced into a body of water — possibly a crater lake, meltwater from snow or ice, seawater — and the very large contrast in heat (sometimes upwards of 1100°C between water and basalt) causes an explosion of both the water and magma. This is called fragmentation, and ash can be produced during these explosions, meaning what could have been a lava flow becomes an explosive eruption. The 2010 eruption at Eyjafjallajökull in Iceland was initially a phreatomagmatic eruption when the explosive phase started — the erupting magma came into contact with the melting icecap on the volcano and gave it extra explosive oomph — and helping Eyjafjallajökull go from being an eruption that only Icelanders and enthusiasts would note to one that brought Europe to a halt
MBL reports there is still no confirmation that an eruption is in progress.
The Civil Protection Science Board “is meeting now to consult on the issue.” The news comes on the heels of earlier reports from RÚV of a 4.5 magnitude earthquake near Askja, stating, “Models of the intrusion, based on GPS measurements of land deformation and earthquake resolutions, indicate that about 20 million m³ of magma have entered the intrusion over the last 24 hours; 3-400 million m³ since the beginning of the episode, on Aug. 16.
The intrusion also seems to have caused considerable stress in the bedrock over a large area, including the vicinity of Askja.”
An annoucement on whether or not an eruption is in progress is still pending.
It is hard to compare this intrusion to any other that we have instrumental data on. The main reason is that we have not seen one like this from a mantleplume volcano, nor have we seen something like this from a rift volcano.
It has a little bit of semblance from the Krafla Fires rifting episode. But I think that comparison is just too simple. First of all that was a much thinner intrusion that never reached this deep, so it was never even close to get down to the mantle. And the most obvious thing is that it kept to its own fissure swarm.
This intrusion has now been inside 3 different fissure swarms, and has the potential for more magma output when it breaks to the surface. In a way it is much closer to how the Skaftár Fires (Lakí) looked, but that eruption also seems to have stayed within its own fissure swarm.
two possible solutions for the shape. One is a bottom closed intrusion with no mantle contact, and the second is a full Skaftár Fires version with a wedge shaped obloid intrusion open down to the mantle.
I currently think we have the first option, but that it is really close to the mantle and that it sooner or later will turn into option two. If I am right this will most likely lead to an increased risk for a flood basalt event.
The rift is now 45 km long and roughly 17.5 km high. Calculating the width is though a bit more interesting. If we take the east and west dilation between the Dyngjuháls (DYNC) and Kverkfjöll (Gengissig, GSIG) is by now 44.5cm. To get the correct values we have to take to recognize that the GPS-station are a bit far from the rift so the value is larger. Now, if we compare with the apparent dilation on further out stations we can roughly calculate that the true value is around 135cm. That would make the current volume of intruded magma into 1.05km3.
The big mystery is where the water might flow. A huge flood in Jökulsá á Fjöllum glacial river has been feared, but there is no indication that the water level has increased there. Another possibility is that the water has flooded into Grímsvötn, glacial lakes, but then the icecap by the lakes should have risen. Measurements are not available on that yet.
Should melt water have flowed into Grímsvötn it would be collected there before a flood would start to the southwest of Vatnajökull glacier. This happened in the river Gjálp in 1996 when a bridge was swept away, hence closing the Iceland Ring Road.
Víðir Reynisson, director of the Civil Protection Department, told RÚV that the calderas are located further to the south than expected. Hence, it is difficult to predict where a possible flood would occur, to the north or south of Vatnajökull.