![yearly_activity[1]](https://wattsupwiththat.files.wordpress.com/2014/08/yearly_activity1.png?quality=75)
From the Icelandic Meteorological Office:
A summary of seismic activity, written Tuesday evening 19th August 2014 at 20:00
Around 1.000 small earthquakes were detected in the Bárðarbunga region from midnight (18/19) until Tuesday evening 19th August at 20:00. All of them were smaller than magnitude 3 and most were located in the cluster east of Bárðarbunga.
While the northern cluster close to Kistufell has calmed down significantly following the M4.5 earthquake on early Monday morning, event rates in the eastern cluster are still high. Similar to recent days, two pulses of comparably strong seismic activity have been measured between 04:00 and 08:00 this morning, as well as 16:00 and 18:30 in the afternoon. The cluster east of Bárðarbunga continued to slowly migrate northeastwards today. Events are still located at around 5-12 km depths, no signs of upwards migration has been seen so far.
Below is a summary map of all manually revised earthquakes since the onset of the swarm, which illustrates the migration of earthquake activity during the last days. Earthquakes in the map are colour coded by time, dark blue dots show the onset of the swarm on Saturday, orange dots Tuesday’s events until 19:00, light blue and yellow are the days in between. The time scale is days since the onset of the swarm.
Map by Gunnar B. Guðmundsson, Icelandic Meteorological Office.
via WUWT commenter “unmentionable”:
From the quotes below it sound like they’re crossing their fingers and toes that this thing stays underground and does not get any bigger. the longer the tremor goes on like this the worse its going to be if it pops under 2,000 ft of water ice.
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Magma flowing into Bárðarbunga caldera with great force – 20th August 2014
http://www.visir.is/magma-flowing-into-bardarbunga-caldera-with-great-force/article/2014140829931
Kristín Vogfjörð, seismologist and research director at the Icelandic Meteorological Office, says that the activity is very powerful. “This just keeps going on. This is many times more powerful than what’s been going on in recent years.” Kristín says that a large volume of magma is flowing under the caldera, heading northeast towards the Kverkfjöll mountain range. The magma is staying at a depth of 5-10 kilometers – there are no signs of it moving any closer to the surface. If asked if an eruption is due to happen in the next few days, Kristín responds: “Not necessarily. There’s nothing suggesting that it’s about to. But due to the size and scale of the activity there’s full reason to be vigilant and prepare for an eruption.”
Magma surge towards the surface would be very powerful – 20th August 2014
http://www.visir.is/magma-surge-towards-the-surface-would-be-very-powerful/article/2014140829927
Kristín Vogfjörð, research director at the Icelandic Meteorological Office, says that the current seismic activity at Bárðarbunga is many times more powerful than any on record for the site. “It’s very powerful,” she says. For comparison she notes that thousands of quakes have been measured at Bárðarbunga in the past week, but in the Gjálpar eruption in 1996 they were only a few hundred. … “While this is going on, it may never reach the surface. But we still need to keep an eye on it because the volume of magma is incredible,” she adds. …”There is no indication that it’s moving further up than that. But if it were to happen, it would happen very quickly,” Kristín states.
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Joel O’Bryan says:
August 21, 2014 at 6:06 pm
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I just saw that on the USGS map listed at 4.8. That is a step up from the others.
Goldminor says:
August 21, 2014 at 6:37 pm
If the magma movements are following forcing flow movements by tidal influence, then expect a few low ~ 3.0 to 3.5 mag jolts 4-8 hours after the 4.8 as the magma recedes back down its channels.
The magma, though viscous still can surge with each high tide where it takes 30 – 90 minutes to break down an old solid dyke barrier to advance up further in the caldera plug and cause another big jolt. But the tides are waning from now through Tuesday, and don’t start back waxing until Wednesday. Thursday is a BIG tidal movement. So if she doesn’t break through to an eruption by Saturday, then she probably won’t until Wednesday or Thursday.
But all this breaking of an old hardened dyke barrier is nonlinear, and all it could take is just one more snap to make a clear path to the surface to start venting very hot gasses to the underside of the ice pack, then anavalance of water into the caldera… KA-blooie. So nothing ever is for sure at this stage of a volcanic evolution, she also could simply go bakc to sleep for a few years. But i wouldn’t put money on that outcome at this point.
I want to make some more distinct big-picture observations about the seismic pattern we now see. The continuing activity in Bardarbunga is much shallower, almost all above 9 km depth, than the activity directly under the Dyngjujökull fissure-swarm, which is almost all above 25 km depth.
The fissure-swarm quakes extend down vertically under the fissure as deep as 35km, and seem to get deeper by the day, suggesting deep displacement of rising material above the quakes and rapid dynamic pressure adjustment flows in the upper mantle under a large plume. This magma is not only in the region of 5 km depth, rising material is extending at least 15 km below that, directly under the fissure conduit.
This does not suggest to me that Bardabunga’s role is to feed magma horizontally into the fissure network. Bardarbunga is inflating, we just aren’t seen quakes below about 11 km there, presumably due to a lack of sufficient constriction in the feeder conduit. It is free to flow below that (and that is why it is a mature caldera).
The fissure network however is being feed by a sheet-like full through-crust rift conduit directly down to the elevated asthenospheric melt source area. Despite early interpretations of horizontal migration from Bardarbunga (which may have been correct initially), the distension of the fissure has lead to increasing and much deeper quakes, directly under Dyngjujökull, which shows horizontal feeder input is no longer the predominant mechanism here, as deep mantle access has now opened in the fissure system, which will release deeper melt intrusion access to shallower depth. This magma will be very hot and very gassy and will want to expand as it rises, which will open the fissure further.
The big picture looks like an oversize pulse of magma has been rising slowly for years and has finally applied enough stress on the crust to force it apart and intrude below Bardarbunga. Then the excess rush of magma from Bardabunga opened the connected fissure swarm(s), and this has triggered a deep pressure change under the fissures, as magma was then freed to rise into them directly, as well.
This served to then temporarily reduce the deep flow into Bardabunga as it diverted into the deep new fissure opening at the base of the crust (which is 15 km thick, btw). So the quakes at Bardarbunga fell away for several days. But as the fissure is now becoming constricted by the rapidly rising magma pushing it apart, the excess flow into Bardarbunga has resumed once more and is inflating it.
Hence the stronger and more numerous earthquakes in the caldera. if this continues the caldera will begin to fill, as the former fissure swarm that relieved the flow pressure is now filling up as well. So it can only remain in Bardarbunga and accumulate. Unless the fissure system breaks open along its length first to ease the magma influx pressure from below Bardarbunga.
This plume behaviour also accounts for the strong chemical similarity in the magma composition across the four local calderas, and the extensiveness of the crustal connectivity and the extensional responses that created these multiple ducts and flexi-chambers for magma to rise within.
The deepest quakes are down to 35 km and are possible pre-sequence stress/tension relief quakes that can trigger a larger tectonic regional quake sequence.
Such crustal tension relief then leads to a deep confining pressure drops, and this induces pressure-reduction melting of the crust and upper asthenosphere simply due to less confining pressure so rock crystal molecules can liberate into liquid phase. Opening fissures up fully will have similar effects, a partial pressure melting of wall rocks will feed further magma into a protracted high-volume fissure eruption (which just seems to go on … and on).
This looks like a preparatory setup for a high volume eruption (which could take weeks to occur … or hours). And we’re for the first time seeing in detail how earth manages to generate and flow large volumes. Much will be learned from this given and many modern instruments have been deployed to capture it.
Joel O’Bryan says:
August 21, 2014 at 9:11 pm
Goldminor says:
August 21, 2014 at 6:37 pm
Joel, I hope these ‘tides’ you mention are not moon-tides.
This system is not at one atmosphere, it is high temp and high pressure, there are no ‘tides’, there is only a war between confining pressure (including overburden weight) and dynamic magma pressure. It is pressure which overrides everything else. The magma demands more room, so it rises in pressure until it gets it. If it does not rise high enough to overcome mechanical strength of confines the stress of ever more magma rising creates supersonic shocks via breaking the confines. That is what the quakes are.
There is no advancing and retreating tides. Retreat to where?
The deeper you go the higher the higher the static confining pressure becomes? The shallower the less the static confining pressure. It is not going to go up a gradient! It is going to go down gradient. And it can not reverse because there is about a 10 k column of rising magma behind it.
It only goes up, or it goes sideways if the structures present will allow that (if the pressure of the magma or induced quake shocks can overcome the mechanical resistance of the structures via fracturing them (btw, dikes (or ‘dykes’ if you prefer) are vertical oriented structures, not horizontal structural ‘barriers’ to a vertical rise as you’ve described).
Unmentionable,
There is a weight component (mg) to the magma flow. There cannot “not” be. It is dense molten silicate rock with water and gasses dissolved at very high pressure. And Yes, the gas-phase pressures are rising as the fluid pressure drops to allow them to evolve, which makes this a very explosive type magma compared to say Hawaii. I understand that simple physics. It is inevitable that somehow they (the hot gasses: H2O, HF, H2SO4, SO2, CO2) will be released as the gasses evolve out as the very high pressures drop in the fluid. This will push steam into the fissures looking for a surface route to atmospheric pressure.
But that said, even at high pressures 5-25 km down, the tidal forces still act. They can pull on a 20 km^3 massive molten blob of rock, just like they pull on the massive ocean bodies. But it is not rigid, it is plastic and flowable. The rhythmicity of the tides (yes lunar) cannot be ruled out when new magma is breaking through old hardened dykes. I’m talking pressures that combine the (mg) term that is under the influence of tidal forces, not actual movements that take hours. That said, there may be some movements too as the pressure gradients stratify the magma pulse into different phases of evolution based on depth.
I am not trying to start a technical argument, but there does seem to be a tidal component to the seismic activity related to the magma flow. In most cases it seems to be delayed at 30-120 minutes from the Hofn tidal charts (nearest I could find), as the high tide pushes in and then waxes. Those could be real pressure changes on a significant mass of molten rock too even “just” 10 km down.
JMO
The Icelandic Seismic and geophysical observational networks are about as good as it gets. All that investment and work is about to pay off.
—
From: “Development and Implementation of Seismic Early Warning Processes in South-West Iceland, 2010 to 2012”
http://en.vedur.is/media/vedurstofan/utgafa/skyrslur/2010/2010_012rs.pdf
“Results of the application of the automatic fault mapping procedure to a few large earthquakes in SW-Iceland
Introduction
During the 18 year operation of the SIL automatic seismic system in Iceland, the network has recorded foreshocks before all medium to large earthquakes in SW-Iceland. If such foreshocks can be located with high-precision before the following main shock occurs, the foreshocks may already have delineated the fault plane of the coming main shock, thus allowing its fault plane to be immediately inferred and providing early-warning mechanism information.
High-precision earthquake locations, with optimum achievable location accuracy on the order of tens of meters are currently obtained through relative relocation (double difference) of manually located earthquakes (Slunga et al., 1995; Hjaltadóttir and Vogfjörd, 2005). The objective is to obtain this location accuracy in near-real time in the SAFER region of SW Iceland (see Figure 1) by starting with the less accurate automatic event locations, available 2 minutes after the origin time (OT), and further developing the existing relative location method to operate automatically and in near-real time. The procedure will make use of the existing database of waveforms from previous relatively located events, many of which have already been used to map sub-surface faults. Using this approach earthquakes can be automatically located with high precision, they can possibly be associated with previously mapped faults, or can illuminate new faults, all in near-real-time. … ”
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Awesome network. Looks as though they have been busy redeploying a lot of the mobile recon elements around Bardarbunga this week, so the data flow and picture should continue to improve.
Unmentionable,
Thank you for the long technical discussion at 9:43pm.
I would probably enjoy discussing this over a beer (or two) with you one day.
I really hope “she” doesn’t explode, because “she” has the real potential someday to be another 1783 Laki, as they both likely draw on the same very deep mantle source.
I have no intention of disputing lunar tides in magma conduits mate. I will act as though I didn’t hear of lunar tide control of magma pressure or compositional differentiation layering based on moon tide control (and no, a website link won’t ameliorate my skepticism).
Joel O’Bryan says:
August 21, 2014 at 11:30 pm
Unmentionable,
Thank you for the long technical discussion at 9:43pm.
I would probably enjoy discussing this over a beer (or two) with you one day.
—
Yeah, probably, though I suspect we would disagree on mechanisms 😀
Note the same Bárðarbunga behavior, as in a drop in seismic levels, and maybe just before a moderate >3.0 (or so jolt). In another several (3 or 4) hours???
http://en.vedur.is/photos/jarvatj_rit/140822_0630.png
Disagreements are good in science. No 97% consensus crap.
True enough re consensus, but the pressure flux needed to generate such periodic and escalating quakes are sufficiently accounted and predictable from prosaics.
Another day of multiple in-moderation comments …
I understand shot noise from EE (an MS EE) as a prosaic, but shot noise is probabilistic, and not determinant. What I see in the seismic data at question is quasi-deterministic. If I am correct the swarms will continue but the higher activity stuff will fade until around Wednesday into Thursday, when the 4.0+ stuff will start again.
All the comments for the Icelandic volcanologists about “large volume” and “very powerful” are to be taken with the respect they deserve. Dismiss that at peril.
And I also wonder…
Can Katla be far behind?
Unmentionable wrote, “It only goes up, or it goes sideways if the structures present will allow that (if the pressure of the magma or induced quake shocks can overcome the mechanical resistance of the structures via fracturing them (btw, dikes (or ‘dykes’ if you prefer) are vertical oriented structures, not horizontal structural ‘barriers’ to a vertical rise as you’ve described).”
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My thoughts:
I’ve always thought of dykes as vertical obstacles to flow (in volcanoes at least!!). If I wrote something that implied horizonta, I admit that is wrong, I was wrong.
Fracturing of the old semi-solid rock VERTICALLY-oriented dykes is what is causing the seismic jolts. No doubt. Spreading the channels and filling the caldera. With this level of activity “she” is going to release.
Yes, the crust is a network of dike swarms to depth in spreading centers, nearly to the surface as well. But this magma is moving mostly via displacements pushing existing structures further apart. If the rate if extension is too low and pressure is too high a larger magmatic quake then results where the structure is broken to form a cavity that is intruded at supersonic speed of the medium. This imparts a shock wave, that then usually triggers more local distension of the crust which allows more magma in.
Actual shocks cause flow, in both liquids, and supersonic transient flow deformation of of solids, even high pressure rocks behave like a fluid until the shock passes by.
So this reduces pressure until more magma arrives to repeat the cycle once again. As the magma encounters a structure it can’t overcome so easily it takes time to build the higher pressures and shock energy intrusive release, needed to move further.
Eventually the Earth quakes become more numerous, as the small quakes can’t make enough room fast enough, and much more magma is surging in behind as well. That is when eruptions are usually triggered at shallower depths, via a major fracture path opening, all of a sudden. The magma then decompresses supersonically into to. If it has to stop again, because of further confinement, it’s going to impart quite a shock wave to the surrounding rocks, transiently deforming them like a fluid in the process.
The pressure means their is no backflow, no retreat, and no retreat even mechanically possible.
PS: please don’t call a magma flow ‘she’, people who call ships and countries a ‘she’ are weird.
>>>Strongest earthquake yet in Bardarbunga<<>>The latest update from the Icelandic Met Office (07.00 GMT) <<<
The seismic activity at Bárðarbunga volcano is still continuing at a high rate, nearly 400 events had been automatically detected at 06:30, but it has slightly after 2 AM, and even more decreased now, between 6 and 7 AM.
As before, the events are mainly located beneath Dyngjujökull/east of Bárðarbunga, depth ranges from 8-12 km but (very few) events as shallow as 3.8 – 4.5 km were observed farthest north/east.
The activity has partly migrated (very) slightly northwards, compared to last night.
For the past days several events have been measured at the Bárðarbunga caldera, at 2-6 km depth. The largest one occurred last night at 23:50 UTC, of magnitude 4.7 (detected by EMSC with a magnitude of mb 4.7 and by NEIC mb 4.8; our alert magnitude was 4.7).
These events probably occur due to pressure changes when magma from a magma chamber beneath the caldera is intruding eastwards into the dyke beneath Dyngjujökull. After midnight only one event reached magnitude 3.0, others were small.
—
Source:
Updated 22.08.2014 09:18 GMT/UT
http://www.ruv.is/frett/strongest-earthquake-yet-in-bardarbunga
>>>Strongest earthquake yet in Bardarbunga<<
A 4,7 magnitude earthquake was detected in the Bardarbunga caldera shortly before midnight last night, the strongest one yet. Seismic activity has however been decreasing since midnight, according to the Icelandic Met. Office. The quake is associated with pressure changes beneath the caldera.
From midnight until 6.30 this morning, nearly 400 seismic events had been automatically detected around Bardarbunga; most of them in the eastern cluster, towards Kverkfjoll. According to the Icelandic Met. Office, the activity decreased after 2.00 GMT and even more between 6 – 7 GMT.
The 4,7 magnitude event, detected at 23.50 last night, is thought to be associated with pressure changes in the magma chamber underneath the Bardarbunga caldera, as magma migrates north and east, into the dyke intrusion beneath the Dyngjujokull outlet glacier. Nothing indicates that magma is migrating towards the surface under the glacier. The 4.7 event was detected widely, here is a link to the US Geological Survey´s website.
The evacuation order for the area north of Vatnajokull is still in effect. The area north of Route 1 (including Dettifoss, Hljodaklettar, Asbyrgi) is still open to the general public.
This story, by the Icelandic National Broadcasting Service (RUV), was updated on 22 August 2014, at 08.45 GMT.
Updates in English will be posted at: ruv.is/volcano
>>>Strongest earthquake yet in Bardarbunga<>The latest update from the Icelandic Met Office (07.00 GMT) <<<
So about 3 hours after Joel's 3 to 4 hour call, nice. Do you do market opening calls?
Agust Bjarnason says:
August 22, 2014 at 2:40 am
>>>Strongest earthquake yet in Bardarbunga<>The latest update from the Icelandic Met Office (07.00 GMT) <<<
"Seismic activity has however been decreasing since midnight, according to the Icelandic Met. Office."
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That is a perfect example of what I was describing above, a large quake makes more room for the magma, so less and smaller quakes follow, until the magma pressure comes back up. Hence; "Seismic activity has however been decreasing since midnight, according to the Icelandic Met. Office."
Interesting Icelandic and multinational Web:
“FUTUREVOLC is a 26-partner project funded by FP7 Environment Programme of the European Commission, addressing topic “Long-term monitoring experiment in geologically active regions of Europe prone to natural hazards: the Supersite concept”. The project started 1 October 2012 and has duration of 3.5 years. The supersite concept implies integration of space and ground based observations for improved monitoring and evaluation of volcanic hazards, and open data policy. The project is led by University of Iceland together with the Icelandic Meteorological Office…”
http://futurevolc.hi.is/
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Agust Bjarnason says:
August 22, 2014 at 5:46 am
That’s great stuff, the more we get this planet wired everywhere, the more we’re going to learn things we’ve never even suspected or observed. In a century or so we may actually be able to produce a cohesive story of how this and other planets really tick.
—Met Office: 25 km long dyke formed—
ruv.is/volcano 22.08.2014 13:46 GMT/UT
A 25 kilometer long dyke intrusion has formed, north and east of the Bardarbunga caldera. Intense seismic activity continues there. Strong earthquakes have been detected in the caldera itself, but they are associated with decompression of the magma chamber beneath the caldera.
According to the Icelandic Met office (www.en.vedur.is) there are no signs that seismicity is decreasing. A 25 kilometer long dyke has formed in the crust under the Dyngjujokull outlet glacier at 5 – 10 km. depth. Magma is thought to countinue to move along the dyke, possibly branching out at the NE end of the dyke.
Several strong earthquakes have been detected in the Bardarbunga itself; the last one, magnitude 3,5, at around 11 GMT this morning, These events are thought to reflect an adjustment of the caldera rim, related to decompression in the caldera since the beginning of the unrest six days ago.
Land displacement measurement with GPS around the volcano show up to 14 centimeter drift since the unrest began, on August 16. Annual drift in Iceland, due to crustal plate movements, is about 2 cm.
„A new GPS station in Kverkfjöll is now running and sending data. Similar seismic instruments were installed by Kverkfjöll yesterday, as well as close to the GPS station at Hamarinn, which was set up two days ago. In addition, two seismic stations set up in Dyngjujökull yesterday are collecting data on site. This work is done in collaboration between IMO, the Institute of Earth Sciences and collaborators in the European FutureVolc research project.“ (Icelandic Met Office).
The evacuation order for the area north of Vatnajokull is still in effect. The area north of Route 1 (including Dettifoss, Hljodaklettar, Asbyrgi) is still open to the general public.
This story, by the Icelandic National Broadcasting Service (RUV), was updated on 22 August 2014, at13.45 GMT.
Updates in English will be posted at: ruv.is/volcano
Volcano cafe has an informative ‘Friday’ type post up with advice, etc., but the comments are especially interesting, especially this one on top, that was re-posted by commenter ‘Spica’:
http://volcanocafe.wordpress.com/2014/08/22/a-note-to-tourists-not-only-for-bardarbunga-and-dyngjujokull/comment-page-1/#comment-131586
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Good news about the other sensors coming online, I stumbled on the Kverkfjöll CGPS link only about an hour ago, it shows the expected large horizontal displacement after the hiatus. It shows movement east and south, which is what you’d expect being on the east of the opening SW to NE fissure swarm. But what else it shows is the highest uplift so far. Kverkfjöll and Grímsvötn are both rising, so the east side close to the fissure has been pumped up significantly since the main stepped-up phase of seismic activity began at Bardarbunga around May 11th this year. Here it is, GSIG:
http://strokkur.raunvis.hi.is/gps/GSIG_3mrap.png
Another shallow significant quake near the center of Bardarbunga.
2.7 NNE Bárðarbungu mag=3.5 an hour ago depth=3.6km quality=99%
Today has certainly has seen a qualitative change in the quakes. The quake pattern within the fissure complex NW is of relatively smaller quakes, and the largest of them are at the bottom of the 15 km high stack. This suggests that either there’s more material trying to flow into the fissure there, or else the area has become more constricted. The CGPS shows instead it has continued to open wider, then it must mean more material is trying to rise into the fissure complex more quickly as it opens more. Magma is apparently trying to rush into it from below.
The quakes in Bardarbunga are more focused in the caldera and much larger than any to date. This continues the rise in numbers and mag trend established yesterday. The quakes are all stacked central to the caldera within 10 km of the surface, with mag ~3 top and bottom, and the big mag 4.7 right in the center around 5 km depth. The magma has begun to lift and stress Bardarbunga’s collapsed roof-plug structures.
As a result I don’t think it’s now reasonable to say there’s no evidence of magma rising towards the surface. If magma were not accruing and rising higher the bigger quakes would not be there. So the magma chamber is pressurizing and no longer able to relieve its pressure via flowing out into the fissure complex, as the magma in it has risen and is now pushing back.
Which means the pressure will soon be rising everywhere within the two main intrusions, or else it will try to extend the opening and infilling of the fissure complex to the SW. But Bardarbunga may have to develop a ‘head’ of higher magma pressure before that takes place – it may not open.
I can’t see the caldera filling much without extending and squeezing all the fissures full of magma that it can, and it may now have done that. At which point lifting the roof of the caldera is the only outlet left to ease the influx of magma pressure.
Opinion: from what is observed so far I think magma will continue to rise even if a large eruption commences, because the quantity of magma on the rise as delineated by the numerous rapid-fire quakes down to ~25 km, suggests a very large volume of melt is moving, and much of it is well below 10 km depth still. If a large eruption occurs the pressure drop will result in a renewed rising magma surge.