BrickFielder

Certainly a suggestion of instabillity perhaps post frontal during the early to mid evening today. Lapse rates through the middle layers look steep enough for a storm. The trouble is that it is not exactly surface based (sbcape is weak) and the forecast SkewT does not look that good. I am not totally convinced and model agreement is not particularly good, but certainly some potential for rotating cloud. Updrafts are probably not strong enough to lift low level vorticity though. Worth keeping an eye on.

Potentially the storm south of Cambridge has split with a right moving storm to the south. This particular storm may have some tornado potential.

Different models not entirely in agreement about the potential today, except perhaps that there is a risk of storms developing in east Anglia late in the afternoon. Lincolnshire and Norfolk late afternoon appear to be prime locations for potential. Mid level lapse rates are not stunning but seem enough to give storm potential. (26 degrees difference typically needed for a storm but above 30 is ideal, so 28 is within the realms of possibility) Triggering for storm potential is a bit more tricky. There is some post frontal vorticity which declines as the front moves away , there is not much in the way of on shore winds , little I the way of low level wind convergence and slim evidence of orographic lifting (effect of hills and mountains) playing a part. What I think we are left with is some questionable low level convergence. If they do materialise then netweathers NMM model shows some interesting mid level vorticity as a result of developing storms. With model agreement tricky it is hard to pinpoint today. There does appear to be low level wind speed shear today so a strong updraft could pick up low level vorticity. Directional sheer through out looks poor which generally speaking you would see from a marked tornado risk. Storms can and do make their own environments and that is what I think the NMM mid level vorticity charts are suggesting today (You could get a surprise). Since temperatures are not that high today, lapse rates are not outstanding, and instability is not the high the risks of a severe storm today are pretty low. Key areas would be eastern England late afternoon and perhaps a line just north of the M4 corridor.

I am currently keeping an eye on Sunday for some potential. Current Fax chart suggests a trough moving through. A little instability is forcast. Too early at the moment to put much in the way of detail and it can all change. The problems are its a post occluded front trough rather than a warm sector trough , so the temperature is likely to be limited. Lapse rates are not that impressive either with skewt's suggesting potential weakening caps at 550hpa and 800hpa heights. Still winds look light which could mean some under estimation of surface temperatures and there appears to be a modicum of low level wind speed sheer. Not your classic thunderstorm conditions, but just enough to keep an eye on how things develop in the charts especially if the jetstreak to the south shifts a little or is delayed a little.

Latest from the scientific advisory board. Seismic activity in Tungnafellsjokull glacier had decreased but activity in Bardarbunga is still strong. http://en.vedur.is/media/jar/Factsheet_Bardarbunga_20141020.pdf From the geoscientist on duty During the last 24 hours around 70 earthquakes have been detected around the Bárðarbunga caldera rim, the strongest was magnitude 5.3 at 08:36 this morning on the northern rim. The event was preceded by a magnitude 4.7 in the same area just two minutes before. http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947 Not sure whether the time proximity there is important, although it was noticed. Jon Frimann posted an interesting link on his blog today Jon's Blog http://www.jonfr.com/volcano/?p=5171 Interesting Link http://www.os.is/gogn/unu-gtp-sc/UNU-GTP-SC-10-1103.pdf This is a paper talking about one of the volcanoes to the south west of Bárðarbunga along the rift zone. I think it has some interesting possible insights into the what is happening at Bárðarbunga. Some Quotes Worth a read even if you think each individual volcano is different (probably true). Subsidence seems to have stalled a little bit at the caldera and while this might be significant it has happened before. It may be that the trend will continue given a little time. There looks to be a little bit of an anomaly on the HAFS monitoring SIL at the moment which could be weather related but could be worth keeping an eye on. http://jardvis.hi.is/gps_timaradir_vid_bardarbungu

The facts It is now the largest eruption in Iceland since the eruption in Laki (Skaftáreldar) in 1783 – 1784 eruption. The eruption at Holuhraun continues as does the subsidence at Bárðarbunga caldera.The lava field (60 square kilometers) continues to grow. The subsidence of the caldera is 35 m and continues at the rate of 30-40 cm/day, mainly in the NE part. The volume of the subsidence is 0.75 square kilometers. Seismic activity in Bárðarbunga continues but with less large earthquakes. Over the weekend there appears to have been a period of earthquake activity on the south western part of the caldera rim although that appears to have stopped.There also appears to have been some activity just outside the caldera rim to the north east including a 5.2 magnitude earthquake on Sunday at 03:22 at a depth of 0.1km. Deeper earthquakes at around 5.5 to 7.5 km deep seem to be a trigger for more subsidence although these seem to have reduced somewhat (subsidence rate does not appear to have slowed much though). The scientists dont seem to be able to keep up with verifying the number of smaller earthquakes, which might well reflect that they cannot keep up with the work load over a long period or that they have more important analysis to do. The speculation bit. There has been some speculation that the uneven subsidence of the caldera over short time periods (Hours) may be due to an interaction with melted water and lava causing little steam explosions or even that there has been a minor eruption in the caldera. I remain to be convinced off either scenario. It appears to me that the subsidence is a little more uneven over night which could be the effect of melted water re-freezing in newly developed cracks. As to why we are seeing earthquakes outside the caldera wall at shallow depths then I think the northern part of the caldera wall is starting to become unstable (could slump inwards if the ice does not hold it up) (starting because I think you need another couple of months of subsidence before it really becomes a problem). There is no news on the caldron development near the caldera but there did appear to be some earthquakes over the weekend between Bárðarbunga caldera Tungafellsjökull. The eruption covering has expanded but does not appear to impacted the river that much at the moment with the icelandic met officeshowing a new map of the coverage obtained with a fly over by the coast guard (perhaps we might get to see some updated radar images once they are processed or some news on the caldrons). http://en.vedur.is/media/jar/myndsafn/full/Yfirlitskort_20141019.jpg Over the last week there has been a little swarm of activity at Tungafellsjökull volcano which is just to the north west of Bárðarbunga and there has been speculation that it is at risk of eruption. The Authorities in Iceland dont seem to be that keen on an eruption happening based on the new risk and danger areas mapped out. http://en.vedur.is/hydrology/articles/nr/2963 That reluctance to see the potential at Tungafellsjökull volcano might be due to the fact that the volcano has not been active in thousands of years. This I think means that magma within its chamber might well have partially solidified. I also have a suspicion that the rifting event may have increased compression in Tungafellsjökull volcano. This does not mean the swarm is not extremely concerning, just that I suspect the scientist are taking a number of factors into account which we might not know about. (Blue lines are meant to represent crustal movement around the fissure) An unconfirmed twitter report from the university of iceland field team suggests that there has been more degassing at the Holuraun vent site compared to previous weeks. I cannot locate a sensible explanation for this, but my guess would be that the magma being erupted has had less chance to degas elsewhere in the plumbing. I think degassing occurs when pressure on magma drops which would suggest it no longer passes through a lower pressure zone on its way to the surface. This could mean the feed for the vent is now mainly from a deep source or that the pressure in Bárðarbungas magma chamber is no longer low enough for degassing to happen there. This is all speculation off course on a unconfirmed report. The Icelandic Red Cross had an emergency exercise opening 48 emergency shelters on Sunday the 19th. In addition there are reports of a meeting in Reykjavík over the weekend for the volcanic hazards group. This seems to have unnerved a few people in the blogosphere that they know more than they are telling, but I suspect a period of relative calm is being used to pool knowledge, ideas and check preparedness. Other discussions in the blogosphere have contemplated whether the volume of lava erupted is equal to the volume of lava displaced by subsidence at the caldera. The subsidence volume appears to be 0.75 square kilometers and the erupted volume aproximately 0.5 - 0.8 square kilometers. This could be coincidence since it sort of implies there has been very little new magma into the system, yet at least some change in pressure or flow must have set off initial events. It sort of suggests to me the eruption should continue as lava at the surface should have less volume than magma compressed in a magma chamber. It concerns me that too much might be read into the match in volumes. GPS movements seem slight and to reflect the current wind direction. Tremor charts seem to show increased activity yet most of that will be due to weather conditions, but a light pick up in the 0.5 to 1 hz range might suggest a slight uptick at the eruption sight.

Some earthquakes yesterday which interested me. Date Time Depth Magnitude Location 14.10.2014 14:18:51 0.1 km 2.2 8.4 km SSE of Bárðarbunga 14.10.2014 14:02:43 1.1 km 0.8 8.9 km NE of Bárðarbunga 14.10.2014 09:41:33 0.1 km 0.8 8.3 km N of Bárðarbunga 14.10.2014 09:01:49 0.1 km 0.9 14.8 km S of Bárðarbunga Now at least a few of these look like being just outside the caldera. This suggests to me that the flow from deep under Bárðarbunga to the SE into the fissure might be close to the surface again to the south east of the caldera. I would expect some more cauldron activity to the SE as heat and gases melt more ice here. I dont see much correlation between subsidence at the caldera and the wider rifting (shown up on KIDC FJOC and HAFS monitoring) episode although I suppose it takes time for rock to shift. Having said that the DYNC and VON monitoring stations still show continued crustal movement. It is hard to tell whether these movements are due to uplift/subsidence or crustal movements due to rifting. I see most of the activity on the north east edge of the caldera as being related to subsidence but one or two earthquakes just outside the caldera make me wonder whether there are some wider shallower ring faults there. There has been some speculation on some blogs whether Holuhraun is forming a new volcano. While I think the fissure has tapped into a deep source at around 13km which is linked to a magma chamber or feed under Bárðarbunga at about 10km deep, I don't see Holuhraun as having its own seperate magma chamber. So my opinion would be it is not a new volcano, but more of a rifting cinder cone. Others have speculated that a small eruption is actually occuring in the caldera and the subsidence is due to ice melt. Personally I think you would be likely to see caldrons form if any significant eruption was taking place in the caldera , but then what do I know. My guess is that the Icelandic coast guard is making regular flights using there radar monitoring (TIF-SIF) which should be able to tell the difference. http://en.vedur.is/about-imo/news/nr/2953 http://www.lhg.is/frettirogutgafa/frettir/nr/2834 http://www.ldeo.columbia.edu/edu/polareducation/Activities/Remote%20Sensing%20Radar/SeeingThroughtheIce_032712.pdf

GPS signals suggest to me that crustal deformation has calmed down a little. Perhaps there is just a touch of uplift indicated , possibly towards the fissure eruption or the caldera, it is very difficult to tell which from these charts. Compare this with the movements seen last week. So no obvious large movements. Both the DYNC and VON Sils show a little uplift over the last day or so. It would be difficult to point to where exactly the uplift is even from these charts, but it suggests to me that more magma is coming up from deep than can be erupted at the moment. Vonasgard temor mointoring shows some evidence of increasing tremor in the 2- 4Hz range. This suggests to me deeper rock breaking as magma moves up from a deeper source. (Magma movement nearer the surface tend to have a lower frequency in my opinion). Does this mean that Bárðarbunga has stopped subsiding. With the battery for the transmitter for the Bárðarbunga monitoring hardware run out, it is hard to tell. Going on past episodes it seems very unlikely that the subsidence is not continuing. Yesterday there were quite a few deeper earthquakes (11- 13km deep) east of Kistufell which I think is below the fissure, which might suggest magma from this level trying to push up to the shallower levels. Quite a few of the earthquakes this morning have not been verified yet so it is hard to see if this is continueing. Geo Scientist on duty reports Over 100 quakes have been registered during past 24 hours in the caldera and about 25 in the northern part of the intrusion. http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947 My best guess wiould be that the eruption might pick up for a little bit or even start at a new point over the next few days. The caldera subsidence is an unknown quantity, although I would guess that it is continuing. There has been a bit of dicussion on various blogs about some new cauldrons having formed at the caldera. It is not clear whether these are in the caldera or just outside like the previous ones. This would suggest to me some geothermal activity has gone on and magma is closer to the surface than it has been. My best guess would be that the feed from Bárðarbunga into the fissure is more active. I could be completely wrong about this and they could be in the caldera, equally cauldrons take time to develop so they could be from previous activity. There has also been some discussion about the amount of Chlorine type gasses being emitted from the eruption along with the SO2. Sounds to me like the cocktail of gases emitted can be pretty unpleasant. Any interpretations in this post are my amateur ones and you should bear in mind that phyiscal equipment at the remote sites is subject to harsh conditions which may actually reflect other conditions than those I interpret.

Yes I see. All the on duty geoscientists are having a cup of tea or in a meeting and need time to catch up.

In my last post I suggested something a little different happened Tuesday night and I wanted to show why through the GPS charts provided by the Iceland Met Office. My perspective is that there was a lot more movement after the earthquake at 4km deep on Tuesday evening. Recent GPS charts from the University of Iceland suggest movement has gone back to gentle subsidence. I personally thought this might have been a bit of a game changer but having looked at the charts it seems things have returned to a steady state of eruption at the fissure and subsidence. Well maybe a little drop off in eruption intensity, but some of the tremor reduction may well be due to weather conditions changing. I am starting to see some periods of activity in the subsidence at the caldera. In the following chart I have marked out segements where I think activity slightly changed. First up was the immediate period after the tuesday evening earthquake, then a quieter period, followed by resumption of the subsidence and earthquakes and now a slightly different period again. These do not appear to be periods or cycles of unusual activity, but repeating cycles. The cycle I think we are in at the moment is one of the ring faults failing at a relatively shallow depth. These are some of the earthquakes from this morning and over night. Date Depth Strength Location. 09.10.2014 06:38:10 64.662 -17.443 1.1 km 1.2 90.01 4.7 km ENE of Bárðarbunga 09.10.2014 04:28:50 64.681 -17.310 1.1 km 1.2 75.99 11.3 km ENE of Bárðarbunga 09.10.2014 03:01:50 64.673 -17.485 1.1 km 1.0 74.72 4.2 km NNE of Bárðarbunga 09.10.2014 01:47:17 64.681 -17.440 1.1 km 1.1 90.02 6.1 km NE of Bárðarbunga 09.10.2014 01:46:03 64.685 -17.465 1.1 km 1.1 45.66 5.8 km NNE of Bárðarbunga 09.10.2014 00:37:17 64.617 -17.387 1.1 km 1.3 90.01 7.2 km ESE of Bárðarbunga 08.10.2014 22:44:40 64.678 -17.496 1.1 km 1.4 90.01 4.4 km NNE of Bárðarbunga 08.10.2014 21:26:10 64.679 -17.450 1.1 km 0.8 90.01 5.7 km NE of Bárðarbunga These are all earthquakes at a particular depth (1.1km). Perhaps we should not read too much into these because they are not the strongest earthquakes and may be the types of earthquakes which can be hidden by bad weather conditions. We have also had quite a shallow strong earthquake yesterday evening which will most likely have shaken up the ice covering of the caldera. Date Depth Strength Location 08.10.2014 18:48:58 64.671 -17.451 0.1 km 4.6 99.0 5.0 km NE of Bárðarbunga It looks like a ring fault failure from its location , but it does tell us that ring faulting is reaching the surface (as if we did not know based on the subsidence). Unfortunately we cannot really see what is going on with the eruption or whether the river has been further impeded at the moment, so I have a bit of a challenge for any enterprising person. Can you map out where the ring faults are, reverse faults and magma chambers are based on the following earthquake map from the caldera (No I am not saying its accurate) To get you thinking I have done an example of where they might be. Seems to me there may be an angle to the plumbing below the caldera and rather than being wider at the top it might be wider at the bottom. Current suggestion are that there is probably a magma chamber at around 10km deep, but there are also suggestions that there might be shallow chambers at 2km and 6km. My personal theory is that there is a sloping magma chamber roof at about 6 to 8 km deep. You should also bear in mind that typically the shape of magma chambers is not exactly uniform. That is a representation of yellowstones plumbing.

Just a quick note to say I think something a little different happened overnight. Bearing in mind the weather conditions are poor in the area of Bárðarbunga and there is ample reason to see false signals I still think something a little different happened. It looks like there was a slight uplift and then a marked drop at Bárðarbunga. We have seen this a number of times before so at first glance nothing seems unusual. There has even been speculation that this bumping around is something to do with how the ice reacts in the caldera. What strikes me as different is that this appears to be picked up on other SIL's. These are extracts from the full SIL charts. This looks like a marked eastwards movement at vonaskard (VON SIL) with a smaller movement eastwards at HAFS, while there appears to be a movement westward at DYNC. Bearing in mind weather conditions (blue lines on tremor charts tend to pick up) there does not seem like much evidence in a pick up in magma movement near the surface (red and green lines on the tremor charts). A possible culprit is the following earthquake Monday Evening 06.10.2014 22:00:20 64.677 -17.410 4.0 km 3.8 99.0 6.9 km NE of Bárðarbunga. To me this looks more like a slip fault earthquake on the ring fault. Something a little different from the normal even if it is not. I think this shows how the crust is being deformed and this might just be a relaxation in stress. I would not be surprised to see earthquake activity reduce a little now and for the eruption site to see a little spurt of activity through this morning. As usual this is my interpretation and may well be wrong so make up your own minds.

I tried to do some analysis on the earthquakes and those that possibly show reverse faulting. I was typically looking for earthquakes within 3km of Bárðarbunga and thought there may be some sort of pattern. Date and Time Depth Magni Location. 04.10.2014 21:58:01 7.7km 1.3 0.5km NE of Bárðarbunga 05.10.2014 16:24:41 7.7km 1.8 0.7km SSE of Bárðarbunga 04.10.2014 16:53:12 7.9km 1.4 0.9km NW of Bárðarbunga 06.10.2014 03:40:53 0.7km 0.9 1km ESE of Bárðarbunga 04.10.2014 19:58:59 6.8km 2 1km ESE of Bárðarbunga 05.10.2014 16:25:05 10km 2 1.6km WNW of Bárðarbunga 05.10.2014 07:31:25 6.3km 0.7 1.6km NW of Bárðarbunga 05.10.2014 09:58:20 6.9km 1.5 2km NW of Bárðarbunga 04.10.2014 18:07:41 4.2km 2.1 2.1km SSE of Bárðarbunga 05.10.2014 15:55:49 7.8km 1.4 2.2km N of Bárðarbunga 04.10.2014 22:19:26 9km 3.2 2.2km SE of Bárðarbunga 04.10.2014 22:07:38 5.3km 1.7 2.2km NW of Bárðarbunga 05.10.2014 02:19:27 0.8km 3.4 2.4km S of Bárðarbunga 05.10.2014 08:25:57 1.5km 3.8 2.7km WSW of Bárðarbunga 05.10.2014 09:46:41 5.7km 1.7 2.8km W of Bárðarbunga 05.10.2014 03:44:24 5km 3.6 2.9km SSE of Bárðarbunga The problem is that the focal point of Bárðarbunga is probably not dead center of the caldera and as far as I can tell tends to be more west and north than the actual center of the caldera. Having said that there does seem to be evidence of reverse faulting going on. 7.5 to 8km deep seems to show some evidence of being a favoured depth. The 9km and 10km depth earthquakes most be close to the magma chamber if estimates of the magma chamber depth are correct or even in the feeds into the chamber. Analysis of earthquakes possibly outside the caldera rim tend to be located to the north east. Looking at the daily GPS measurements on the IMO site I think there is a slight tendency for uplift towards the north eastern edge of the caldera rim. The Vonaskard GPS seems to move slowly eastwards without interuption. http://en.vedur.is/earthquakes-and-volcanism/gps-measurements/bardarbunga/ http://jardvis.hi.is/gps_timaradir_vid_bardarbungu So results are pretty inconclusive in my opinion from the earthquake data, but the reason I was interested was due to the following paper. http://www.academia.edu/8344720/Dike_emplacement_at_Bardarbunga_Iceland_induces_unusual_stress_changes_caldera_deformation_and_earthquakes I was interested to see whether current earthquakes confirmed the areas of tensile and compresive stress suggested in the paper. Although I think the stresses are different across the caldera area I am not sure I am totally convinced by the arguments in the paper. So what does it matter anyway ? I am thinking that areas of tensile stress would develop gaps for magma to rise into, which might suggest areas away from the north east part of the caldera might be most likely to see an eruption. Areas of compression are likely to see an eruption when stresses are reduced or when the eruption begins to die down due to lack of magma feed. Thats guess work on my part but the later of the two scenarios feels more sensible to me. Then I wondered whether bookshelf faulting has played a part. http://gef.nerc.ac.uk/documents/reports/914.pdf I initially thought the odd angle of the fissure may be due to this, but I think it is at the wrong angle. The second thought was does this just apply to areas between the fissure zones or would it apply to the caldera floor as well. So you dont think so, to be honest neither do I, but it might interfere with stress zones, limiting their effect as the book like blocks bend. Incidentally there are some good diagrams it that particular paper which are well worth a look at even if you dont want to read the full paper. So is there anything more we can learn from the krafla fires eruption episode and deformation and stresses induced. http://web.gps.caltech.edu/~avouac/publications/Hollingsworth_JGR2012.pdf Not much except that the caldera moved eastwards as it subsided and there is a risk of dikes freezing if not feed from a deep source. So enough about Bárðarbunga and its caldera, although I would just say that there have been a few earthquakes outside the caldera rim to the NE today, what about the lava reaching the river. Unfortunately weather conditions in Iceland mean we cannot really tell. It is suspected that the river is now being pinched in a few places with the possible prospect of a lake developing at some point in the furture. Enough rambling for today and make sure you take my views as the light heighted bumblings of the village idiot. In other words I am not an expert.

Lots of noise on ther tremor charts from the weather over the last day so I am looking at those charts with a sceptical eye. There is also a bit of dicussion on blogs about the Bárðarbunga GPS measurements and whether there really is some sort of bouncing around on short time scales. Haraldur Sigurðsson's blog seems to be the source of the conversation with a suggestion that perhaps there is ice melt contributing to the caldera subsidence and perhaps the small bouces are a result of this. I think the GPS plots need another look at in terms of what they suggest. This seems to be the GPS device nearest the eruption and I would interpret this as showing a rifting event which is begining to wane in its intensity. That is not to say the eruption will stop, but rather the fissure near to the GPS device does not appear to be opening up more. This is south west of the caldera and would suggest to me movement during the rifting period and then some uplift towards Bárðarbunga. This is north west of the caldera and would suggest to me movement during the rifting period and then some uplift towards Bárðarbunga. Lets try to visualize this on a map of the SIL positions. This might suggest some sort of uplift towards the western/ south western edge of Bárðarbunga's caldera. Taking a closer look though and both the HAFS and VON GPS dont show significant up down movement, so any uplift must be very near to Bárðarbunga. Yet we know that Bárðarbunga caldera is subsiding. I dont buy into the fact that subsidence in the caldera is solely about ice melt. Surely any melt water would be seeping down to cause problems deeper down or going somewhere ? We have however seen some earthquakes which look suspiciously like ice quakes. Monday 29.09.2014 15:10:12 Depth 0.0 km Magnitude 2.5 5.1 km ESE of Bárðarbunga. Zero depth but very big for an icequake. Seems more like a crack opening up in the caldera floor due to all the bouncing around to me. Whats with having very few earthquakes in the south west corner of the caldera. Ok so we suspect that the ring faults are different at different points around the caldera. From one of my previous posts. This kind of makes me think about trap door collapses of calderas and the 1968 collapse event in Fernandina (Galapagos) . Even that does not feel right. Perhaps there are multiple magma chambers like Grímsvötn with one feeding the north fissure and one the south fissure. Again I am not convinced since it does seem to be slipping as a single block. The difference in the ring faults might explain parts of it, but there might be another reason. Yes here I go into back into the whacky world of theory. We suspect that during the krafla fires eruption to the north of Bárðarbunga that fissures north and south of there may have come under compression as the fissure opened up, only to relax some considerable time after the eruption. Kind of like. So you could have compression pushing up the caldera to the south while magma flow and expansion let the caldera drop to the north. The problem is I dont quite see the transition from compression to expansion occuring across the relatively small scale of Bárðarbunga's caldera. Yet another theory with more holes in it. Have you noticed that most of the big earthquakes that cause subsidence in the caldera seem to occur between 5 and 8km deep and often close to 7km deep while other earthquakes even if quite large dont seem to affect the caldera. Certainly seems worth thinking about as to what exactly is happening at that depth (we have a suspicion that the magma chamber is down at around 10km). 29.09.2014 13:42:58 Depth 5.6 km Magnitude 5.5 8.5 km ESE of Bárðarbunga There is also discussion on blogs about whether the eruption is being fed from Bárðarbunga's magma chamber. Personally I think this is half right, in that the magma source is essentially the same for the eruption and Bárðarbunga's magma chamber but the flow is not direct from the magma chamber any more, but from the deeper source. Back at the eruption and there are suggestions that the northern flow of lava which crossed and wiped out the road in the area may have come to a stand still, while flows to the south towards the river have picked up. I think it will be interesting to see how far it gets over the next day or so and its impact on the river. As ever there is a caveat emptor on anything I write, in that these are very amateur observations and I dont expect anyone to buy into what I am thinking. Still it is fascinating and perplexing.

Some indications for me that one earthquake is triggering another today. 24.09.2014 03:41:42 Depth 7.4 km Magnitude 1.8 99.0 4.9 km N of Bárðarbunga 24.09.2014 03:40:52 Depth 7.3 km Magnitude 1.8 99.0 5.4 km NNE of Bárðarbunga 24.09.2014 02:28:08 Depth 8.1 km Magnitude 2.0 99.0 3.1 km SE of Bárðarbunga 24.09.2014 02:27:08 Depth 8.9 km Magnitude 1.9 99.0 3.3 km SE of Bárðarbunga 24.09.2014 02:20:18 Depth 8.1 km Magnitude 0.8 99.0 7.0 km NNE of Bárðarbunga Similar depths but different places along the caldera ring. Eruption at Holuhraun seems to have formed a Y shape or at least lava flow seems to have created a Y shape. We probably should remeber that the fissure will most probably be affected by the stresses and strains caused by Askja at its northern most extent. Slight pick up in the tremors being picked up on the Vonaskard Sil This could be the effects of weather, but looks like a small pick up in activity after a slight lull over night. Bárðarbunga caldera appears to be still slowly sinking with occasional large drops prompted by larger earthquakes 6 to 7km down. GPS measurements dont really suggest a general dropping around the volcano. Can be found at the following link http://en.vedur.is/earthquakes-and-volcanism/gps-measurements/bardarbunga/ Think this suggests that the eruption is unlikely to stop in the immediate future and there are indications that magma might be moving elsewhere in the system. Vonaskard Sil seems to be showing a leveling off in subsidence which to me means outflow of lava and new magma into the system is fairly balanced. Instead of whacky theory today I thought I would try to explain how in my amateurish way I interpret certain things. Tremor Charts 0.5 - 1 hz is a relatively lower frequency (red lines) and I would take to indicate magma movement high up in the crust and even eruption. 2 - 4 hz is a higher frequency (blue lines) and usually indicates earthquake activity and tends to be more associated with shifts and movements lower in the crust. There are of course exceptions especially where there is gas or water movements involved. I base this on the following. GPS Measurement Charts I interpret these in the following way Only it is more complicated than that in that during a rifting event plates move apart as well. We should also remeber that as the rifting event dies back then there is some relaxation and the plates can move a little back in the other direction. There can also be ice on antennas or faults in the measuring devices (See GFUM SIL at the moment possibly). So it is tricky and cannot be looked at in isolation. Other Reports I assume many of you will have looked at Jón Frímann Blog http://www.jonfr.com/volcano/ and the posts at VolcanoCafe http://volcanocafe.wordpress.com/ and the IMO updates http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947 but what about Rei's blog at the daily kos. http://www.dailykos.com/blog/Rei Here are some pictures from that blog Ok so just a little whacky theory for today. The plumbing system beneath Bárðarbunga may not be uniform. Here is an image of some modelling of a plumbing system beneath a rfiting volcanic area. This suggests to me that there may be a curve somwhere in the magma chamber where possibly some crystal mush could be dropping off into the deeper chamber. Perhaps pushing magma up into another part of the plumbing. As ever when I go off into the whacky world of theory take everything I say with the knowledge that it is about on par with the understanding limits of Homer Simpson.

GPS Shows a bit of a wobble in the downward movement around Bárðarbunga GFUM Sil seems to have ice on the antenna again. I would take this to indicate that the flow of magma into Bárðarbunga over the last 24 hours has matched or exceeded the eruption quantity. Which begs the question why subsidence at the caldera seems to be continuing. Although we should note that earthquakes have been somewhat deeper. So here we go into the whacky world of theory again where I get everything wrong again. It turns out that inside a magma chamber not all magma may be in the same state. Some may be partially solidifed and some might be crystal mush and some might be very liquid magma. If there is a new injection of magma then some of the crystal mush may be reheated and become more liquid. When it does so I am guessing it will expand a little and put pressure on the magma chamber walls and roof. You would think this would tend to push up the caldera, but it may also push the walls of the chamber outwards. In a rifting environment are the walls more likely to move or 3-10km of caldera roof ? If it is the walls expanding then the ring faults would be moving outwards as well. Possibly causing the caldera to drop within the ring faults. Ok some more links for those interesting in reading some more in depth thoughts. ftp://seis.es.uwo.ca/pub/ktiampo/magma/Stress_magma_chamber.pdf http://www.geotop.ca/pdf/stixJ/Kennedy_et_al_Nature_2008.pdf As ever dont take anything I say too seriously as I might well be incorrect.

Looks like we had two ice quakes on Saturday. 20.09.2014 15:35:14 Depth 0.0 km strength 0.7 5.1 km ENE of Bárðarbunga 20.09.2014 14:07:33 Depth 0.0 km strength 1.3 3.8 km SE of Bárðarbunga Both are slightly away from the caldera rim. Also some very shallow quakes Saturday evening 20.09.2014 19:32:41 Depth 0.1 km strength 1.3 6.9 km ESE of Bárðarbunga 20.09.2014 19:26:34 Depth 0.1 km strength 1.5 4.1 km NNE of Bárðarbunga This could be ice quakes or reverse faulting. There was also quite a large earthquake which was very shallow on Saturday 20.09.2014 17:05:47 Depth 0.1km strength 4.4 3.6 km SSE of Bárðarbunga That definately looks like reverse faulting as it is not on the rim. Sundays 5.5 magnitude earthquake which caused the drop was down at a depth of 8.9 km and probably on a ring fault (7.1km ESE). This suggests that the ring faults might be quite vertical (more likely to slip) or that an upper magma chamber floor could be collapsing into a lower chamber. Today sees a quite deep earthquake 22.09.2014 03:39:00 Depth 11.6 km strength 1.4 4.5 km ESE of Bárðarbunga That looks more central than on the caldera edge. I am also seeing more evidence of once earthquake triggering another. 22.09.2014 03:13:57 Depth 8.7 km strength 3.7 5.0 km NNE of Bárðarbunga 22.09.2014 03:16:33 Depth 9.1 km strength 1.4 5.0 km NNE of Bárðarbunga Interesting that the sequence was downwards rather than upwards. Earthquake map for Vatnajökull seems to show activity migrating more towards the ice. GPS Map seems to show GFUM SIL moving towards the eruption site (could be ice on the antenna again) which might suggest a new fissure could open up towards the ice. Over stations dont show much movement at all. Vertical Bardabunga chart seems to suggest periods of calm after bigger earthquakes which cause a drop. The readings look a bit more spiky recently which may be due to weather but also seems to happen just beore anoher eathquake and drop. Even the 180 minute smoothed line looks a little jolty (again could be the weather). Tremor charts suggest to me show a slightly elevated amount of eruption over the last 24 hours. I think it might be an idea to keep wathcing the vertical displacement Bárðarbunga to see if it steepens as I am looking at a pattern of slight weakening of the caldera floor, earthquakes triggering others (possibly more widespread slipping on ring faults rather than isolated slips), some possible ice quakes which might alter the caldera floor loading. As ever this is all quess work so go read the experts views at the IMO or university of iceland and dont take anything I say to seriously.

Pick up in tremor at skrokkalda(skr) http://hraun.vedur.is/ja/oroi/skr.gif Looks like possible magma movement with nearest volcanoes Harmarinn or Tungnafellsjökull. Not showing up clearly on the vonaskard SIL so possibly more likely Harmarinn. Could also be SIL mal function or weather ?

Following on from yesterdays musings I thought I would explain a premise that perhaps subsidence at Bárðarbunga preceded the eruption or more specifically a little injection of magma could cause subsidence which caused the eruption. A potential model of the magma chamber. A little injection of magma lubricates a solidified block of magma in the chamber and it begins to slip down. The solidified block acts as a plunger on the magma forcing it out along a wider ring fault into a fissure. The solidified block slips further trying to pull down the caldera roof. Water seeps into the area above the solidified magma causing little steam eruptions which bump the caldera floor. The caldera floor begins to slip on its ring faults and reverse faulting cracks open up. Or on the other hand the magma chamber could be more like an hourglass shape as explained in the following paper. http://rses.anu.edu.au/~hrvoje/Tkalcic_etal_BSSA2009.pdf

Plenty of Earthquakes at Bárðarbunga caldera today and another meter drop acording to the GPS with a smattering to the north west of the caldera which seems new. One or two earthquakes under the eruption site as well but not as proflici earthquakes wise as earlier in the month. Latest notes from the meeting of the Scientific Advisory Board took a slightly different tone today. Seismic activity http://en.vedur.is/media/jar/Factsheet_Bardarbunga_20140918.pdf The options are now. Eruption declines or large scale subsidence of the caldera occurs with or without a major eruption. This suggests to me a deep level of concern about the caldera collapse. Ok so thats the update over and now I will go off into my own wacky little world of theories (madness). I have been wondering whether the Bárðarbunga magma chamber may have similarities to the Skaergaard intrusion based on the gravity anomalies (higher densities under Bárðarbunga which may be linked to gabbro). I thinking that there may be hardened magma along the walls celining and through part of the magma chamber. The Skaergaard intrusion is thought to have developed under Greenland when the mantle plume currently under Iceland was under Greenland. It is also thought that a narrow sill fed the magma chamber from the top. Reading the following paper though I would really have to question this idea. The paper also poses a number of other questions. For example for the mixing of old and new magma which is suggested there has to be a quick (possibly less than a year) an significant injection of new magma into the magma chamber for the magmas to mix properply. http://petrology.oxfordjournals.org/content/early/2012/09/27/petrology.egs061.full Somewhere I read that at spreading plates magma chambers should be like upturned boat hulls in shape. Equally depending on the rate of spread the magma chambers should be more pear shaped. Or combing the two (you would expect earthquakes away from the caldera if this was true) Now we know there is some sort of magnetic anomaly in Bárðarbunga suggesting dense rock or solidifed magma so perhaps the top of the magma chamber looks like this. Which makes me wonder whether the caldera sits on base rock or solidifed magma and if there was a layer of solidifed magma in the chamber what was above it, upto the magma chamber ceiling. As ever I am probably talking rubbish, but one explantion for earthquakes being all the way down to 10km (providing the magma chamber is not down below 10km) is that solidifed magma in the chamber is breaking up some how. Perhaps even subsidence and rifting preceeds eruptions? Perhaps I better leave it to the experts to muse on these things. Oh here is a very easy to read document about the atlantic plates covering iceland as well. http://www.southampton.ac.uk/~jtc/fierydeep.html

I personally think the tremor chart for vonasgard sil shows lower lava intrusion into the fissure. From this I would expect the eruptions to die down if it conitues. GPS time series charts to me do not suggest much in the way of the fissure opening up more or much uplift. http://earthice.hi.is/gps_time_series_around_bardabunga_0 I thought I would do a little anlysis on the earthquakes around Bárðarbunga's caldera to see if there was a depth at which there were no earthquakes. Firstly I looked at earthquakes over the last 48 hours and picked three likely depths 4km to 4.5km and 1.7km to 2.7km and below 10km. Looking back further and I picked up earthquakes in those regions above 10km. I thought I would do some more analysis to see if larger earthquakes were on one particular part of the caldera and the answer seemed to be perhaps NE or NNE but not exclusively. Perhaps I could pick up information by analysing distance from the center of the caldera and depth or location. There was perhaps a suggestion that deeper earthquakes were more central. I guess more detailed spectral analysis of the earthquakes is required to pick up any patterns. What I hoped to see was an area at the magma chamber where there were no earthquakes. Perhaps a particular weakness in the ring faulting above the magma chamber. Not finding something can off course be as informative as finding something in scientific terms. Perhaps there is no shallow magma chamber ? Perhaps the magma chamber walls are partially collapsing ? Do earthquakes potentially below a magma chamber centrally indicate opening up of dyke intrusions into the chamber and how quickly could it refill ? Well at least one mistery has been partially explained and that was why the GFUM Sil GPS plot was showing a rise. The reason being that the antenna was iced up. Still when I look at the longer term plot it seems like a partial explanation (still looks like a bit of inflation and deflation allowing for correction - smothing of east/west plot movement). Some quotes from another paper which might interest This suggests a magma source or plumbing system linking up icelandic volcanoes somewhere between 10-15 km deep (perhaps between the new crust and older subducted old crust ?) It also suggests the caldera crust might be brittle, but I should point out that I think other papers would contest this. It all looks to me like we will get possibly multiple phases of activity over a longer period. Perhaps phase 1 is coming to a bit of a halt. As for what is going on in the caldera I am not sure but perhaps the university of Iceland Report gives us some clues. That sounds like some sort of collapse has happened before to me. I have also read about some gravity anomalies in Bárðarbunga which have been atributed to asperities or gabbro. So again I am not sure. As ever I am not an expert and you should take everything I say with an open mind to being completely wrong.

A quick update on one or two things today. First up the GPS change map from the IMO web SIte. The first thing I notice is the change at GFUM with the GPS displacement gone from pointing towards Bárðarbunga to pointing away from it. This I would interpret as a sinking of Grimsvotn or at least the area between Grimsvotn and Bárðarbunga. This might signal an end to the intrusion of lava into the fissure or that lava is flowing into another fissure. Notice also that DYNC gps measurements suggest the fissure is not really opening up that much anymore (perhaps a little bit in the last 24 hours). VONC GPS measurements continue to point to uplift either at Bárðarbunga or the southern most part of the fissure. It certainly looks like something happened with the magma flow movement around two days ago (especially with the GFUM upward motion reversing) and I am unsure whether it was a stop in the flow of magma into the fissure or a stop in the magma plume or magma flowing somewhere else yet to be determined. (possibly along a new fissure to the north east of the volcano ?) Next up is a picture of the Bárðarbunga GPS. What interests me here is the movement this morning (16th) which shows a marked bounce in the caldera floor. This I think shows just how loose the caldera floor is on the ring faults. Earthquakes since mid day yesterday tending to be a little deeper at Bárðarbunga which may be attributable to ring faults going down from the magma chamber down to a deep magma source. I am guessing here not only does the the caldera floor sink under decompression but perhaps the magma chamber floor does as well. This might let more magma into the magma chamber, so you get a yo yo effect between compression and decompression. Todays earthquakes seem shallower at Bárðarbunga suggesting perhaps a period of decompression again. I have been reading around again through various bits and pieces which some may like to peruse and think about. This particular extract from an article seems to partially explains why the fissure seems to change course as it approches Askja and how stresses interact with Bardarbunga. This one interests me because it indicates the change from inward to outward dipping ring faults is from east to west and implies rather than fragmentation of the caldera floor you might expect the whole caldera floor to move as one. This could imply a very slow collapse of the caldera is likely or that reinflation of the magma chamber could cause problems. I am of course just guessing again or hoping. A very rapid caldera collapse could be very nasty but seems less likely. This interests me because it suggest perhaps you can have an infrasonic wave or pressure wave associated with a caldera collapse. Bearing in mind the worst case scenario of a rapid caldera collapse seems unlikely due to a mixture of outward and inward dipping ring faults. What do you think would be the effects of the worst case scenario (earthquake big enough to affect the UK? tsunami ? a pressure wave ? big sulphur dioxode cloud ? ash ?). Just curious for peoples opinions. As ever anything I post should be taken with a very large pinch of salt and I openly admit the situation has me totally confused and I dont have the training to interpret the information kindly provided by the authorities in Iceland. I just hope better minds can explain the anomalies and puzzles I see.

Its all still a puzzle to me as to what exactly is going on. Just when you think you might have a handle on things the parameters seem to change. Take the following GPS plot. This would seem to suggest that somewhere near Grimsvötn volcano there has been a drop in the surface. Either magma flowed somewhere else or stopped flowing or there has been an adjustment made to the equipment. Yet another puzzle. I am assuming the drop in the caldera is the actual rock surface of the caldera rather than just a drop in the ice cover, but there seems to be a bit of a north south difference. It is suspected that the ring faults on Bárðarbunga are inwards to the north and outwards to the south, so I would have expected the caldera to tilt. That tilting might even affect the flow of magma into the fissure as you get compression on the ring fault to the south and relaxation on the ring fault to the north. So not what I expected exactly. Tremor charts are all over the place with no significant increases where you might expect if conditions were changing. http://hraun.vedur.is/ja/oroi/allarsort.html I did however notice a slight uptick at godabunga which is of course is near katla. This may just be the natural cycle of things there with minor bubbling up occurring regualarly. There also appears to a bit of a jump at kreppuhraun (kre) and smjorgil (smj), which may just be due to the wind or vehicles passing, but has me a little confused as these areas are a distance from Bárðarbunga. About all I can say is that I think at the moment there is no significant change in the eruptions. There are continuing earthquakes at the Bárðarbunga caldera with some being quite shallow. (5.4 km SE of Bárðarbunga 5.4 magnitude at 0.1km). That could be an ice quake , but it seems too big for that. Most likely the ring faulting is happening close to the surface now. The implications of that might be that volcanic warm air can trickle up to the edges of the caldera, starting to melt a little ice. Once water can also trickle down the ring faults there are likely to be little steam explosions which may knock and jolt along the caldera edges. It is also interesting to me that Icelandic met office latest fact sheet on the situation said the following This I think is a possibility with rather than a full collapse of the caldera it continues to slowly sink and tilt with perhaps magma finding a route to the surface up through the ring fault on the northern side of the caldera. Equally there is a possibility that things will all quieten down. My suspicion is that this will not be the case based on the fact that over the last 20 years parts of Iceland have risen over 2 meters (a large part of that may be due to ice rebound after the iceage) which suggests some built up pressure underneath Iceland. Bearing in mind I think things will happen on a longer timescale than some might expect and will be more gradual, I suppose we ought to consider what would happen in a full caldera collapse. Once of the things perhaps not talked about much is the pressure wave or infrasonic wave which could be created. Remember that Krakatoa is reputed to have blasted out windows over a thousand miles from the volcano and rupture ear drums of sailors near by. There are significant reasons why this might not be the case here , not least because of the shape of the caldera deflecting noise upwards rather than outwards, but it might be worth a discussion. My guess would be that a large part of the caldera floor would end up as ash in the atmosphere and anywhere downwind is going to suffer a bit of a deluge of ash. I am also not quite sure what a lump of rock possibly 12km by 7km dropping into a magma chamber would do. Would you get a significant earthquake which could trigger earthquakes elsewhere in the world. Would the crust weaken and let through more magma? What kind of sulphur dioxide amounts would be released into the atmosphere? Too many questions and its all amateur speculation so take anything I say take with a great deal of scepticism, but as ever I hope my musings help better minds than mine to explore things. Perhaps they might even trigger some new avenues of scientific fact gathering (As if). If you are still none the wiser then join the club but I hope you enjoyed the post anyway.

I thought today I would take a little trip back into the wacky land of theory and amateur guess work to try to answer some of my own questions. Sulphur Dioxide Content First up I have some questions about the sulphur dioxide content of the lava and the simple answer seems to be that the lava is Basaltic (as opposed to Andesitic or Rhyolitic). It may be a little more complicated than that though as there are suggestions that older crust may have different levels of sulphur content to modern crust. http://scrippsscholars.ucsd.edu/jmdday/content/anomalous-sulphur-isotopes-plume-lavas-reveal-deep-mantle-storage-archaean-crust I think this may have implications for the source of the magma below Bárðarbunga and perhaps how much existing top level crust is melted into the magma. http://scrippsscholars.ucsd.edu/jmdday/content/phantom-archean-crust-mangaia-hotspot-lavas-and-meaning-heterogeneous-mantle This to me suggests that the magma source is mainly from melting of older crust below the current top level of crust and not much of the possible rubble infill into the Bárðarbunga magma chamber from previous caldera collapses has been melted into the lava. Plumbing One of my questions has been around where the Bárðarbunga magma chamber is and whether parts of the caldera floor are breaking or collapsing which might thin the caldera floor and lead to the lowering of the caldera floor in the center. One research paper which seems to hint at a possibility of this is the following one. http://www.researchgate.net/profile/Vyacheslav_Zobin/publication/223890790_The_fault_nature_of_the_Ms_5.4_volcanic_earthquake_preceding_the_1996_subglacial_eruption_of_Grimsvtn_volcano_Iceland/links/0c96052a0b90eebb7e000000?origin=publication_detail For those that do not want to read the paper then the magma chamber under Bárðarbunga looks a bit like the following according to the paper. Personally I am not convinced and would favour perhaps two chambers with the upper one being partially filled with rock from a previous caldera collapse. I just do not think 7km of caldera floor will bend enough to allow the sinking of the center of the caldera floor that we are seeing. Overview of events today I may post a quick review of events today later.

Very little movement on the GPS Yesterday (09 Sept 2014). This is interpreted as The caldera continues to sink a little but remeber that 18 meters across 12km is not that much. Tremor monitoring showed a pick up in what I interpret as magma movement on the Vonaskard monitor (blue lines). I am not sure I would interpret this as a possible soon to be eruption under the ice. It looks to me that on Sunday magma flow into the chamber beneath Bárðarbunga exceeded the eruption flow and Bárðarbunga may have been going up in height while the caldera was still lowering. Yesterday the eruption and magma flow very much equalled out with very little GPS movement. The lower frequency (2HZ blue ) tremor suggets to me magma movement from late yesterday onwards, yet there has been no appreciable increase in lava outflow. So there remains a question in my mind about where the flow went (perhaps a sub glacial eruption, perhaps it is going deeper , found a new channel ?). Along the caldera rim there seems to be a mixture of earthquake depths, with more microquakes in the top 1.5km which I interpret as in the caldera floor, some around 3km rising to 1.5km which could be ring fault earthquakes or parts of the caldera floor dropping into the magma chamber. Then there are large earthquakes around 6 to 7kms deep, which might coincide with the magma chamber bottom (could this be parts of the caldera roof falling into the magma chamber and causing an earthquake as it reaches the bottom of the chamber?). The final set of earthquakes are deeper than 7kms which range in size which might be related to the plumbing up to the magma chamber or ring faults down to a deeper magma supply. Its still a complete puzzle to me and as always my conjecture should be taken with a large pinch of salt. Why is the eruption sulphur dioxide rich as well ?

Jón Frímann opinion on the shallow quakes near katla. http://www.jonfr.com/volcano/