Readers may recall that the Grímsvötn volcano caused quite an overwrought mess with air travel in 2011 when it erupted. FergalR writes in WUWT Tips and Notes about the nearby Bárðarbunga volcano becoming seismically active:
A large sub-glacial volcano in Iceland – Bárðarbunga – has been having a huge earthquake swarm for the last 24 hours.
The IMO have just raised the eruption alert level on it.
Source: http://en.vedur.is/earthquakes-and-volcanism/earthquakes
From the Icelandic Met Office:
Activity in Bárdarbunga volcano
Seismic activity in Bárðarbunga volcano has increased. A seismic swarm has been ongoing since 03AM this morning, and near continuous earthquakes have been occurring since then. The depths of earthquakes in the present swarm are in the upper crust and their magnitudes are mainly around 1.5; a few earthquakes are of magnitude greater than ML3.
Long-term seismic and GPS data indicate that there is increased unrest in the northwestern region of Vatnajökull glacier, where Bárðarbunga is located:
Over the last seven years seismic activity has been gradually increasing in Bárðarbunga and the fissure swarm north of the volcano. This activity dropped down at the Grímsvötn eruption in May 2011, but soon after, the activity started to gradually increase again and has now reached similar level of activity to that just before the Grímsvötn eruption. Earlier this year, in the middle of May 2014, there was a small swarm of over 200 events and now the present swarm has already generated at least 300 earthquakes.
Since early June 2014, displacements at GPS stations around Vatnajökull (Hamarinn, Grímsfjall, Vonarskarð and Dyngjuháls) show an increased upward movement and away from Bárðarbunga.
Together, these two systems indicate magma movements in Bárðarbunga. Due to increased seismicity IMO has decided to turn volcano Barðarbunga status to yellow. In case of a sub-aerial eruption, an ash plume of potential concerns for aviation will be generated. The updated map is available at the link: http://en.vedur.is/weather/aviation/volcanic-hazards/
At 23:00 on August 16, there is no unequivocal indication that magma has reached the surface.
http://en.vedur.is/about-imo/news/nr/2936
From Morgunblaðið 18 august 2014 @ur momisugly 15:23 GMT/UT
>>Possible volcanic eruption in Iceland<<
A powerful volcano, Bárðarbunga, might erupt in the Highlands of Iceland. The Icelandic Met Office has upgraded its aviation alert status to orange, meaning that a "volcano shows heightened or escalating unrest with increased potential of eruption." Seismic activity is often the precursor of an eruption.
The orange alert is the second highest alert status. The next alert level, red, means that an eruption is either imminent or in progress. Bárðarbunga last erupted in 1996.
Intense seismic activity
According to the website of the Icelandic Met Office: "the intense seismic activity that started on 16th of August at Bárðarbunga persists. Very strong indications of ongoing magma movement, in connection with dyke intrusion, is corroborated by GPS measurements. There are currently two swarms: one to the E of Bárðarbunga caldera and one at the edge of Dyngjujökull just E of Kistufell. At 2.37 am on the 18th a strong earthquake (M4) was located in the Kistufell swarm.
This is the strongest earthquake measured in the region since 1996. As evidence of magma movement shallower than 10 km implies increased potential of a volcanic eruption, the Bárðarbunga aviation color code has been changed to orange. Presently there are no signs of eruption, but it cannot be [ruled out] that the current activity will result in an explosive subglacial eruption, leading to an outburst flood (jökulhlaup) and ash emission. The situation is monitored closely."
Roads closed north of the volcano
Certain roads in the highland north of Vatnajökull glacier, where Bárðarbunga is situated, have been closed due to risk to tourists in the area, including the road to Herðubreiðarlindir to Askja (F88) and Gæsavatnaleið route from Sprengisandur to Askja (F910). Travellers are advised to gather information on road-safety in the area close to Bárðarbunga. This information can be found here.
We will bring you updates as the story develops.
See: http://www.mbl.is/frettir/innlent/2014/08/18/possible_volcanic_eruption_in_iceland/
It is most likely that a possible glacial surge (jökulhlaup) will flow along the river Jökulsá á Fjöllum, see http://en.wikipedia.org/wiki/J%C3%B6kuls%C3%A1_%C3%A1_Fj%C3%B6llum
Erik Klemetti has a good writeup on this volcano complex and there you will also find a link to Dr Dave McGarvie’s twitter. McGarvie says if this turns into a big honker it can last a long, long time.
http://www.wired.com/2014/08/significant-earthquake-swarm-hits-icelands-bardarbunga/
>>New webcam<<
A new webcam has been installed on the glacier looking at Bárðarbunga. The location is at Grímsvötn 30 km away from Bárðarbunga.
See: http://vedur2.mogt.is/grimsfjall/webcam/
(Grímsvötn: http://en.wikipedia.org/wiki/Gr%C3%ADmsv%C3%B6tn).
Speaking of Grímsvötn, a little discussion of GPS applied to volcano ground movement just before and during eruption (puts context to the recent hours of rapid GPS movements I pasted links to above).
http://www.nature.com/news/volcanoes-shift-before-they-spew-1.14498
Ed Martin says:
August 18, 2014 at 10:53 am
” (trim) … McGarvie says if this turns into a big honker it can last a long, long time.”
__
That may not be as much of a problem as it sounds. The volcano’s past eruption character is for large effusive eruptions which are predominantly large lava-flood outpourings from fissures and sheild volcanoes.
It remains to be seen how much ash fall will accompany it though. The 1477 eruption appears to have had a lot of explosive activity as it had a positively weird andesitic magma which you don’t get in mid-ocean spreading rifts, like this one.
Chalk that up to another instance of observation meeting an inadequate accepted theory, or else a peculiar classification snafu.
Andesite is stiff, it does not flow, it clogs, and it degases and violently explodes. That andesitic material was presumably coming out of the main caldera as it created a regional blanket of tephra over most of Iceland. Tephra is everything from very fine pulverised ash and gravel, to large solid rock ejecta blocks which are blasted outward for many miles by powerful detonations and ash plumes.
If it’s just the fissure complexes spilling lava it may not be too bad, but if the caldera clears its throat and sings, all bets are off for a Summer in 2015.
Map showing the area in Iceland where roads have been closed:
http://www.vegagerdin.is/media/umferd-og-faerd/Halendi.pdf
From the Icelandic Met Office:
>>Seismic activity at Bárðarbunga persists – 18.8.2014<<
The intense seismic activity that started 16 August at Bárðarbunga persists. Very strong indications of ongoing magma movement, in connection with dyke intrusion, is corroborated by GPS measurements. Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood (jökulhlaup) and ash emission. The situation is monitored closely.
– – –
18.8.2014
The intense seismic activity that started on 16 of August at Bárðarbunga persists. Very strong indications of ongoing magma movement, in connection with dyke intrusion, is corroborated by GPS measurements. There are currently two swarms: one to the E of Bárðarbunga caldera and one at the edge of Dyngjujökull just E of Kistufell. At 2.37 am on the 18th a strong earthquake (M4) was located in the Kistufell swarm.
This is the strongest earthquake measured in the region since 1996. As evidence of magma movement shallower than 10 km implies increased potential of a volcanic eruption, the Bárðarbunga aviation color code has been changed to orange. Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood (jökulhlaup) and ash emission. The situation is monitored closely.
http://en.vedur.is/ http://en.vedur.is/about-imo/news/nr/2938
Aviation colour code map: http://en.vedur.is/weather/aviation/volcanic-hazards/
Volcano Discovery Update are calling it – Eruption Imminent
Bárdarbunga volcano (Iceland): continuing earthquake swarm & inflation, orange alert
Monday Aug 18, 2014 18:43 PM | BY: T
An eruption of the subglacial volcano seems more and more likely to be imminent. Rapid inflation suggests magma intrusion at shallow depth. Orange alert has been declared today by the Iceland Met Office (IMO).
The earthquake swarm continues intense with so far approx. 2000 earthquakes detected, including about 200 of magnitude 2 and higher. A magnitude 4.5 event occurred this morning NE of the volcano at 6 km depth.
The epicenter locations have migrated from their original cluster location east of the volcano to an elongated area to the NE of the volcano. This would likely be the area a new eruption could start.
http://www.volcanodiscovery.com/bardarbunga/news/46852/Brdarbunga-volcano-Iceland-continuing-earthquake-swarm-inflation-orange-alert.html
__
The seismic activity chart tells the story it’s arced up again after a slight back off. About 70 hours of harmonic tremor so far. The longer it takes to pop the bigger it’s going to be.
http://volcanodiscovery.com/bardabunga-earthquakes.html
Volcanocafe has an interesting analytical write up:
http://volcanocafe.wordpress.com/2014/08/18/probable-eruption-at-bardarbunga/
Thank you for all the info and links, you’re certainly not unmentionable anymore. 😉
Unmentionable says:
August 18, 2014 at 2:29 am
=================================================
Great comments. Thanks for the education.
Emerging pattern is disturbing
Icelandic updates from Vísir – Fréttir – in English
http://www.visir.is/section/FRETTIR07
“… most events are now located between Bardarbunga and Kverkfjoll. … There is full reason to expect an eruption.”
Kverkfjoll is a second major volcanic complex and the past major eruptions were 7,000 to 9,000 years ago and dormant since. Most of the recent earthquake activity (>2,800) is along a 20 km long fissure directly between these two icesheet covered calderas, particularly their eastern sides. The most recent hours of activity are concentrated close to or under Kverkfjoll. The largest quake in Iceland for the past 18 years, of mag = 4.5, occurred under Kverkfjoll a few hours ago, at 6 km depth.
http://volcanocafe.wordpress.com/2013/08/16/kickem-gumbo-ntv-riddle-9/
http://volcanocafe.wordpress.com/2013/08/21/goddali-kverkfjoll-skafta-west-cauldron-iliwerung/
A second major fissure complex associated quake concentration is occurring on a parallel fissure complex around 30 km to the WSW of the two main volcano centers, indicating multiple centers of magma rise into the largest volcanic complex in Iceland.
Looking dicey
Kverkfjöll is a bit of a mystery-bag due to the lack of detailed research, what we do know is this (Smithsonian): http://volcano.si.edu/volcano.cfm?vn=373050
“Volcano Type: Stratovolcano Caldera Subglacial
Tectonic Setting Rift zone Oceanic crust (< 15 km)
Rock Types Basalt / Picro-Basalt Rhyolite"
The Rhyolite tells much about what the heck goes on with this complex. It is a volcanic extrusive equivalent of a granite composition magma. It should not exist in Iceland, it should not be present from a mantle plume derived MOR spreading ridge, but there it is.
And it explains the andesite tephra eruption at Bardarbunga in 1477. If you mix a rising basaltic magma with an existing crystallisation differentiated rhyolite puddle already present under the volcano you can produce an andesitic composition melt and explosively erupted tephra deposits.
Pre-eruption phases of the magma mix and 'fizz' like decompressing champagne after you pop the cork, which mixes the melts vigorously to chemically bulk-homogenise the erupted portion of melt just before and during the resulting explosion. The 'fizz' degassing overcomes remaining mechanical resistance. Next stop, stratosphere. Rhyolite itself produces very energetic explosions and is typically entraining a lot of gas that's exsolved from melt via depressurisation as it rises, but can not easily escape. Thus the rising exsolved gas pressure remains in an unhappy pressure equilibrium that prevents further exsolving of gas (usually copious water, CO2, sulphur).
So ti sits there for a bit, then a large enough earthquake undermines the chamber roof and opens it to 1 atmosphere pressure, and the hot gas instantaneously expands and launches supersonically with the vector for the nearest lower pressure area (i.e. space). Meanwhile the rising magma that had been stymied by pressure and blockage now continues to rise behind this for weeks, or months, and exsolves its gas as it gets closer to the surface numerous explosions result. Ten kilometer across calderas can punch out a lot of magma like this, not to mention two in concert. Hence the deep tephra deposits over regional areas.
So we know both of these stratovolcano calderas do emit highly explosive compositions which can (not will) easily create fine pulverised ash ejected to high altitude within seconds.
But more interestingly there's a shared chemical composition and physical fissure channel linking Kverkfjöll to Bardarbunga with ~100 km of SW to NE trending en-echelon fissure ridges, connecting and over-printing the two calderas.
https://theconversation.com/is-icelands-next-volcanic-eruption-about-to-happen-30642
The Iceland Meteorological Office has increased the risk of an eruption at Bárðarbunga (or Bardarbunga) volcano, after hundreds of earthquakes were reported over the weekend. The risk level has been set to orange, which is the fourth-highest on a five-level scale.
Here we asked Dave McGarvie, a volcanologist at The Open University, to explain what we need to know.
Should we be worried?
We have known for some time that Bárðarbunga was going to do something – we just didn’t know what. Because it is covered in ice, we rely on instruments to reveal its behaviour.
Now it has stirred, it is giving us clues about what it is about to do. The clues from the patterns of earthquakes and earth movements reveal two clusters where magma is moving towards the surface, and if it gets there it will erupt. But whether this will be a gentle or a violent eruption is uncertain at the time of writing.
There is no way to predict when the eruption may happen, but we should get a few hours notice. The good news for air travel is that both clusters are away from the heart of the main volcano which makes it less likely that an eruption will produce the fine ash that causes disruption.
What would the eruption look like?
At the very least, magma will stall in the Earth’s crust and form an intrusion. We may never see any manifestation of this, except on instruments. But if magma does break through to the surface, then how much magma erupts and what is above it will determine the eruption style.
If it is under thick ice – that is more than 400m thick – and not much magma comes up, then a pile of volcanic rock will accumulate at the base of the glacier. This will melt a lot of water (14 times the volume of magma under ideal conditions), and we may see a depression in the ice surface. This will add water to a major river, and cause flooding downstream.
If it is under thick ice and lot of magma erupts along a fissure, then we will see a repeat of the Gjálp eruption of 1996, with erupting magma melting a pathway to the ice surface within hours and forming an eruption plume. Compared to the massive plume of Grímsvötn 2011, this will be a small plume and less problematic for air travel as the particles will not be dispersed widely.
If magma breaks to the surface outside the glacier margin, there are likely to be small but powerful local explosions as the rising magma encounters the water-bearing sediments that occupy the land in front of the glacier margin. Explosion may occur because flashing water to steam involves more than a thousand times expansion in volume. After the water has been used up, or the magma isolated from the water, then a normal fissure eruption would be expected.
I emphasise that the above are what I currently consider the most likely scenarios. The “likeliest” scenario could change at a moment’s notice. That is part of the fun and frustration of anticipating eruptions at poorly-known and remote volcanoes.
What is the worst-case scenario?
That this is the start of a major volcano-tectonic event at Bárðarbunga, which may further develop to the southwest. This is a concern because in the southwest there are fissures that have produced Iceland’s most voluminous lava flows, since the ice melted some 9,000 years ago.
These fissures are up to 100 km long, and far to the southwest they can trigger eruptions at the Torfajökull volcano. Torfajökull happens to have an abundance of sticky magma that can erupt explosively and produce lots of fine ash. The last eruption, in 1477-1480, produced just two lava flows and minor explosions. But the one before, in about 874 AD, produced an explosive eruption plume that was carried over much of Iceland.
Also to the southwest of Bárðarbunga lie the rivers which produce much of Iceland’s hydroelectric energy, and a fissure eruption in this area could cause big problems. Icelanders have long known about this possibility and have specific plans in place should this happen.
I emphasise that we don’t know yet whether this is an isolated event or the start of a more prolonged and larger volcano-tectonic episode. It may be years before we know for certain. But at some time in the future there will be a major fissure eruption to the southwest of Bárðarbunga – we just don’t know when.
Bardarbunga caldera is about 10km wide in diameter. Iceland Geological Survey, CC BY
Could this be another Eyjafjallajökull?
The Eyjafjallajökull eruption caused a lot of disruption to flights in Europe. However, it is important to note that, all things being equal, if an Eyjafjallajökull-like eruption happened tomorrow then there would be far less disruption to air traffic – something less than half the flight cancellations of 2010.
There are two main reasons for this. First is that the old flight rules – avoid all ash – have been relaxed so aircraft can now fly when there is some (but not too much) ash in the sky. Second is that the Met Office revised its model that estimated ash concentrations in the atmosphere, so we now have more certainty about how much ash there is and where it is.
If something unusual were to happen and a substantial amount of magma started rising within the heart of Bárðarbunga, then there could be a large explosive ash-producing eruption. The good news is that we have a better idea of what to expect from such an explosive basalt eruption because we had one in 2011 at Grímsvötn.
To provide context, Grímsvötn was Iceland’s most powerful explosive eruption since Katla 1918, and was about 100 times more powerful than Eyjafjallajökull. Compared to Eyjafjallajökull 2010, Grímsvötn 2011 produced twice as much ash in a tenth of the time.
We were lucky with Grímsvötn 2011, because a combination of wind direction and the new flight rules meant far less disruption to air travel. Over Europe only about 900 out of 90,000 of flights were cancelled in 2011. In comparison, about 94,000 flights were cancelled during Eyjafjallajökull’s 2010 eruption.
Why was Eyjafjallajökull so bad?
Eyjafjallajökull 2010 was a “perfect volcanic storm”. It was unusually long-lived, about 39 days, whereas most explosive eruptions in Iceland last just a few days to a week. It produced an unusually high proportion of the type of fine ash that is most easily transported long distances. Dry weather meant that the ash was not “washed” out of the atmosphere, and prevailing winds carried the ash almost directly to the UK and western Europe. We had the old “ash in the sky so you don’t fly” flight rules which grounded everything. Finally, the old Met Office model slightly overestimated the concentration of ash in the sky.
No knowledgeable volcanologist worth their salt would ever suggest basing western Europe’s ash cloud mitigation plans on a repeat of Eyjafjallajökull 2010, because it is very unlikely. A short-lived but powerful injection of ash into the atmosphere like Grímsvötn 2011 is more typical.
Morgunblaðið 18/8/2014, Updated 19/8/2012 at 12:00 GMT/UT:
>>>Bárðarbunga is still roaring<<>How to pronounce “Bárðarbunga”<<
Icelandic is a notoriously difficult language to pronounce for the uninitiated. It has this massive rolling "R", words that never seem to end and to top it off most Icelanders speak quite fast.
Our latest volcano to make international headlines is Bárðarbunga. Yeah, try saying it. "What is that weird looking D there?" you might think.
To avoid another Eyjafjallajökull disaster, we at mbl.is have taken the time to make a clear and simple guide for pronouncing Bárðarbunga. This is actually how you pronounce "Bárðarbunga". Here it is: http://www.mbl.is/frettir/innlent/2014/08/19/how_to_pronounce_bardarbunga/
Yeah, that’s good ‘n all, but what if its Kverkfjöll? … huh? … we’re in some pretty sh8t now! … I hope they’re working on a plan-B.
__
Apparently both of the caldera’s dimensions are ~8 km by ~4 km and kidney-shaped, presumably elongated along the fissure’s trend line. At least one of them is 700m deep so it’s not brimming with fresh magma so Bardarbunga is probably less of a protracted eruptive threat.
It’s the many years of volcanic quakes under them that gives me pause. The magma chambers may not be full but it does not mean a deep column of material is not stacked up ready to ascend over months or years once it’s decorked.
Relatives of mine are in Iceland now and are touring by car. I sent them this WUWT post. Their response is below (8/19/14). Thanks for the tip.
It is true. M. and J. are inside Of a different volcano as I type. They upgraded the volcano to code orange yesterday. It was code yellow when we were in the flood zone. Since then they have closed the roads into the interior. If it erupts under the glacier it would cause massive flooding in the northeast. We are going to southeast tomorrow so will keep you up to date. Or we may be taking a ferry to Newfoundland and driving home…
Unmentionable says:
August 18, 2014 at 3:33 pm, and several other detailed replies
Ed Martin says:
August 18, 2014 at 7:05 pm, and several other well-thought-out replies
Neil Dunn says:
August 19, 2014 at 3:18 pm
To all above: Thank you for your detailed information, please keep adding your information over the next few days as you find information. Otherwise, only the Drudge Report is providing information worldwide.
Harmonic tremor remains high and is escalating with each new pulse and the period is getting shorter, suggesting intensification of magma pressure as well as flow (from Jón Frímann http://www.jonfr.com/volcano/?p=4728):
http://www.jonfr.com/volcano/wp-content/uploads/2014/08/dyn.svd_.19.08.2014.at_.13.52.utc_.gif
Pressure rise is implied is the rapid ground dilation which continues as magma forces the area apart – note that the Y axis values are double the scale of two days ago:
http://www.jonfr.com/volcano/wp-content/uploads/2014/08/DYNC_3mrap.svd_.strokkur.raunvis.hi_.is_.svd_.19.08.2014.at_.13.06.utc_-754×1024.png
This graphic displays the quakes with respect to the depicted (three) nearby calderas. It’s focussed on the fissure network a present, and is moving along it:
http://en.vedur.is/about-imo/news/nr/2942
A deep column of rising material is indeed rising as confirmed via 3D plot, a teenager created this one. (don’t know why this sort of display isn’t routinely used online, I had 3D depictions like this 15 years ago in a Smithsonian program called ‘Seisvol’):
http://baering.github.io/
Notice the quakes go down to 22 km under the intrusion. As you go down the heat goes up and material becomes more ductile and is easier to plastically deform so if the rate of movement is lower or spread over a larger area, then flow occurs, and not energetic displacements, i.e. quake shocks. The shocks (which are effectively small scale supersonic accelerations within the media, hence shock waves radiate from the area to seismographs) occur where plastic flow deformation rate can not be accommodated. So just because shocks are not present does not mean volumetric flow and buoyancy is not present. The combination of that plot and 96 hours of intensifying high level harmonic tremor and about 3,000 shocks so far means the inflow of material is fast and large.
The dubious good news is that it isn’t focused on a caldera so lava flow may dominate ash. Depends how wet it is. Water makes magma runnier, but it also makes for steam explosions. The fact that it is focused on major fissures means it’s more likely to erupt, as these are always extending with the tectonic quakes, and the magmatic quakes and tremor are dilating the area fast as well.
Eruption is almost assured.
Thankfully not from a caldera at this point. Nevertheless the phreatic explosion a year ago at Kverkfjöll indicated magma is unexpectedly close to the surface under Kverkfjöll and there is potential for sympathetic eruption if it’s pumped with rising magma as well. As the magma erupts pressure regime changes and them a surge of material at lower level can occur that exceeds the flow capacity of the fissure, so it prime-pumps nearby connected magma chambers instead.
As pointed out yesterday, injecting new magma into a chemically differentiated old magma can exsolved gasses that pressurise a dormant system and push it off the cliff.
The thing to remember with earthquakes and volcanoes is they’re not restricted to using old faults or old volcanos. Observations (and energy proportion to mechanical resistance) reveal volcanos and quakes can create a new structures in the crust anytime, anywhere, and may bypass existing large features as if they are not present. A proportion of all new events entirely ignore the existing structures and do their own thing.
Nature huh?
Just to clarify the relative potential of a major fissure eruption, have a read, these can be even more dangerous over all, not merely affecting distant aviation.
http://en.wikipedia.org/wiki/Laki
The system erupted over an eight-month period between 1783 and 1784 from the Laki fissure and the adjoining Grímsvötn volcano, pouring out an estimated 14 km3 (3.4 cu mi) of basalt lava and clouds of poisonous hydrofluoric acid and sulfur dioxide compounds that killed over 50% of Iceland’s livestock population, leading to a famine that killed approximately 25% of the island’s human population. … The Laki eruption and its aftermath caused a drop in global temperatures, as sulfur dioxide was spewed into the Northern Hemisphere. This caused crop failures in Europe and may have caused droughts in India. The eruption has been estimated to have killed over six million people globally, making the eruption the deadliest in historical times.
Major fissure eruptions are not to be trifled with or ignored just because there may be less high altitude ash. (note the surface level hot then cold conditions that resulted)
Patrick says-
Earthquake swarms are not tectonic.
They can be, swarms can occur in divergent zones/ocean ridges which are tectonic.
Barbarbossa (I think) has shown further signs of eruption being imminent but still not certain.
Bárdarbunga volcano (Iceland) activity update
Wednesday Aug 20, 2014 09:17 AM | BY: T
http://www.volcanodiscovery.com/bardarbunga/news/46925/Brdarbunga-volcano-Iceland-activity-update.html
Volcano Cafe – Bárðarbunga update
http://volcanocafe.wordpress.com/2014/08/19/bardarbunga-update/
The last link discusses observed GPS geodetic trends and its crustal relative movement responses. Looks to me the NE end of the fissure must be opening fastest, which happens to be where the last two days of earthquakes were concentrated.
Interesting that Grímsvötn is showing the highest uplift of all of the stations. Some people are sure its not physically connected to Bardarbunga. If not then its filling with a separate injection of magma then? Because its thirty kilometers ESE of the fissure that is inflating.
I read documents yesterday that asserted Kverkfjöll is clearly connected to Grímsvötn via a fissure complex and share the same extrusive signatures. And we can plainly see that Kverkfjöll and Bardarbunga are connected. Frankly I think all of these volcanoes under icesheet are connected. The icesheet itself only exists because of similar deposition, thermal isostasy and magmatic intrusions in the large area.
But why is Grímsvötn and the surrounding ice sheet being pushed upward the most, when the intrusion is so far away?
I suspect it’s crustal rotation or else a buckling response to horizontal displacement as magma forces the fissure apart. i.e. both volcanic and tectonic because dyke emplacement will see to it that the gap does not close again. Hence the ground is not rising elsewhere as much.
If that’s right, and it seems to be, there’s a lot of magma doing that and over a large surface area its pushing on.
Btw, there are more deep quakes recently neat 25km depth under the fissure. This suggests the lower mantle is adjusting to equilibrate density and the static confining pressure gradient after magma has displaced above it.
http://baering.github.io/
The earlier official update I posted is still stuck in moderation land, why I don’t know, seems like every second post goes to moderation, so maybe this one goes through:
Updated summary from Bárðarbunga
A summary of seismic activity, written Tuesday evening 19th August 2014 at 20:00
http://en.vedur.is/about-imo/news/nr/2945
[All should be clear now. .mod]
Iceland Evacuates People Living Near Bardarbunga Volcano
http://online.wsj.com/articles/iceland-evacuates-people-living-near-bardarbunga-volcano-1408536550
http://www.independent.co.uk/news/world/europe/iceland-volcano-area-near-bardarbunga-evacuated-9680962.html