From the Icelandic Met Office
It is believed that a small subglacial lava-eruption has begun under the Dyngjujökull glacier. The aviation color code for the Bárðarbunga volcano has been changed from orange to red. Image follows.
![volcano_status[1]](https://wattsupwiththat.files.wordpress.com/2014/08/volcano_status1.png?quality=75)
Webcam image showing either soil/dust being blown into the air by gas venting or ash being ejected.
Whoa! The plot thickens and the crust thins.
Past 6 hours: Two Mag 5+, and a Mag 4 and one of them is about 5 km east of ASKJA.
A 75 km stretch of over 22 Mag 3-5+ quakes all less than 48 hours.
Snapshot from:
http://en.vedur.is/earthquakes-and-volcanism/earthquakes/vatnajokull/
A graphic created by ‘GeoLurking’ to illustrate the scale of what a rift-fissure eruption can look like if we are seeing its precursor. This eruption sequence lasted nine months (Laki 1783).
http://i1049.photobucket.com/albums/s396/gogglezon/Laki1783toScale_zps40300e0a.jpg
The story so far :
http://i1049.photobucket.com/albums/s396/gogglezon/HourbyHourBardarbungaEarthquakeswithMagnitudefor16thAug2014to27thAug2014H7_zps9b3e3297.jpg
(plot by ‘dfm’)
Nothing bigger than a Mag 3 for past 18 hours. Nothing bigger than a Mag 2.5 in the past 10 hours.
What Mag 2+ activity there is is still under the NNE end of the rift.
Intermission?
It’s just a matter of time until a structure gives. When it does it will be a lot of energy. The harmonic is ‘bearing down’ the same way it did when it was stuck for two days last time. Patience, the next round of quakes will be very big.
Subglacial eruption may already have started.
To-day 6 km long cracks were visible on the surface of the glacier N-E of Bárðarbunga, as well as 4 to 6 km long depressions.
No volcanic activity above the surface is however visible.
The Icelandic Civil Protection Coordination Board has a meeting at the moment and scientists will fly over the glacier early to-morrow. Local time now is 22:35 GMT
The location of the cracks is such that the meltwater surge (jökulhlaup) can flow either to the north or south as in the 1996 eruption.
See http://www.ruv.is/volcano
Morgunblaðið | 27.8.2014 | 22:04 GMT
>>>An eruption either happened or is underway<<<
"Data from the Icelandic Met Office indicates that an eruption took place at some point south of Bárðarbunga or is currently underway.
Melting in the glacier was revealed when the Coast Guard aircraft TF-SIF flew over Vatnajökull tonight. The Met Office said that this kind of melting has unlikely been cuased by anything other than an eruption".
http://www.mbl.is/frettir/innlent/2014/08/27/an_eruption_either_happened_or_is_underway/
Picture from to-day of the glacier’s surface showing the large rifts or cracks.
http://www.mbl.is/tncache/frimg/dimg_cache/e768x432/7/61/761212.jpg
Icelandic Met Office:
“Scientists from IES and IMO on a flight to Vatnajökull tonigth discovered a row of 10-15 m deep cauldrons south of the Bárðarbunga caldera. They form a 6-4 km long line. The cauldrons have been formed as a result of melting, possibly an eruption, uncertain when. Heightened tremor level/volcanic tremor has not been observed on IMO’s seismometers at the moment. The new data are being examined.
Written by a specialist at 27 Aug 22:41 GMT”
http://en.vedur.is/
Some large earthquakes yesterday just after a large high tide on eastern coast. Another similarly large high tide just about to peak, will we see the same pattern?
Also a large depression predicted to pass over iceland early next week, could this provide the stimulus for a large eruption?
http://www.surf-forecast.com/weather_maps/Iceland
Webcam at Kverkfjoll Caldera ~30 km ENE of Bardarbunga – steam with melting snow and ice.
http://cdn.makeagif.com/media/8-28-2014/l63p7w.gif
Kverkfjoll is a twin caldera volcano (so counts as two) that erupts only very rarely. the Camera is facing directly WSW toward Bardarbunga. It is likely this is occurring under the ice over several large areas.
There are now five inter-connected major calderas showing signs of pre eruption seismicity and magma intrusions, and four have had recent visible heating, with ice melt.
Several parallel approximately 10 km SW to NE cracks were imaged in the old lava and ash situated about 15 km south of Askjar caldera, and are visible in high-res imagery from about a 20,000 ft fly-by. Grimsvotn caldera is now known to be directly interconnected via two further fissure networks to Bardarbunga and Kverkfjoll. This fifth caldera is demonstrating abnormal vertical pumping behavior for almost a week. Almost every volcano in the central volcanic icesheet area and a few adjacent centers, noteable Askja caldera, are showing some degree of magma rise and significant earthquake activity signs.
Due to the lack of CGPS station data tracks (GPS geodetic sensors) and concern for the extensional volcanism picture being witnessed and discussed with others, around 20 hours back I personally went hunting for the map positions and names of all other Icelandic CGPS stations,
The result from what was already know from CGPS, plus the three other nearby sites which I identified and retrieved the chart logs from, was then plotted by commenter ‘Irpsit’, at volcano Cafe, and here is the crustal movement vectors which he plotted on a map of the sites, about ten hours ago.
http://s27.postimg.org/98yqr4imr/Sem_T_tulo222.png
There are some errors in the plot but it shows the principle trends sufficiently, namely that the central Iceland crustal-block is currently pulling apart, and has been doing so visibly in the data since about the 22nd of August.
But these vectors are just the first signal of a much more advanced rift divergence, that has already begun to run its course, or already has, at depth. this is the surface catching up to the tensional deformation below.
If you go back in the seismic data for the western Vatnajokull icesheet, there’s a departure point around the 11th of May 2014, where seismicity began to steadily an noticeably rise. I interpret or propose that this was most probably the main phase of tensional divergence beginning within the lower crust, which has only now begun to reach the surface as rifting and heating, due to the material that this accelerated a-seismic extension of the lower crust and asthenosphere produced.
It is clear that this is some level of volcanic rifting.
The overriding question is how wide will it become?
The most northerly three site arrows above are the ones I identified last night, 1 red and 2 cyan. I’ve done this to try and get a better sense of the spreading that may, or may not, have been occurring near Askja Caldera and its fissure zones.
As you can see these site have in about the past 3-days begun to also extend similarly, as they have near to Bardarbunga. So the site are lagging the southern sites, but most probably will continue to extend the crust locally over the coming week, and this allow will promote rifting and forwards propagation in a generally N to NE direction, further opening the current fissure/dike complex as that crust also spreads more, and allows more easy access northwards for the rising magma from below.
i.e. the magma is not coming from Bardarbunga, that concept is clearly wrong on the evidence available.
Askja, will respond even if the fissure does not reach it in diverts, for Askja’s basement is opening up as well and is likely to replicate what is occurring further south and to heat and destabilize, as new material continues to rise into the lower pressure zone opened from below within the lower crust, in that area of highest pull-apart strain near Askja.
Icelandic geophysics experts now acknowledge in an RUV article that data recent reveals some level of rifting and pulling-apart “cleaving” of the central crustal block’s lower crust is currently taking place in a way that may not have occurred for 100 to 200 years.
Seismic activity near the Askja caldera
Fyrst birt: 27.08.2014 13:40, Síðast uppfært: 27.08.2014 15:33
“How much has the land spread? “It´s difficult to say precisely. The intrusion is perhaps 2 – 3 meters wide, but that does not mean that the distance between Egilsstadir and Reykjavik has increased by that; rather the island is being pulled apart, and the landmass on either side is pushed together. But locally, down in the crust, the rock has been cleaved.“
http://www.ruv.is/frett/seismic-activity-near-the-askja-caldera
—
So the question of how big the eruption will be determined via how big the lower crustal cleavage and rifting is.
Amazing! 2-3m wide, 40km long, 20+km deep, filled with 400m m^3 of magma. No wonder they are hoping there will be no eruption, but surely with so much activity it’s only a matter of time.
I think we’re getting to point where we have surface ruptures and no exhalations because the rate of extension still exceeds decomp magma generation and supply, but that’s going to reverse at some point, then magma estimates are going to get real, and unreal.
What I find interesting is other correlations to events that occur during a weakened solar state. That makes me wonder if what we have called grand minima events are more than just a solar event which alters weather patterns. What if there is a geophysical component as well? Something along the lines of a weakened magnetic field which then influences earthquake zones and volcanoes.
Poking around for information to add to a comment, it was easy to see that some events could be connected, such as eruptions at Mt Lassen 1914-1666-900, and on the New Madrid fault 1895-1811/12-1699-1450-900. Volcanoes in Iceland are steady in activity from 1100 and all the way to the present time. Do the larger eruptions fit in with weakened solar activity? Is this part of what determines how deep a grand minimum becomes? Right now it looks like the dominoes are lining up and getting ready to fall into place for the next grand minimum. Even Hawaii is getting in on the act…http://www.nps.gov/havo/planyourvisit/lava2.htm
In the meantime quake activity globally is remaining low. Current EMSC shows 13/24 hour, while the USGS is at 21/24 hour.
In the past 37 hours, only 4 quakes bigger than 3.2+, all in Bardarbunga.
(according to http://baering.github.io/)
But for the past 12 hours, there are four to five Mag 2-3 quakes per hour on the NNE end of the rift. Mostly between latitude 64.7N – 64.9N, longitude 16.95W -16.80W. And Bardarbunga has been quiet for the past 9 hours.
What is the longest erupted fissure in recorded history?
Have two nearby volcanos erupted within days of each other?
http://earthobservatory.nasa.gov/IOTD/view.php?id=83502 – Landsat 8 captured [ash on snow] activity at five of [Kamchatka’s volcanos] during a single satellite pass on April 14, 2014.
http://io9.com/5980899/breathtaking-photos-of-four-volcanoes-erupting-simultaneously-in-russia
Separated by only 180 kilometers (110 miles), Shiveluch, Bezymianny, Tolbachik, and Kizimen were all erupting simultaneously on January 11, 2013.
@Unmentionalble 6:47 am
because the rate of extension still exceeds decomp magma generation and supply
Please expound on limits to magma generation and supply.
Mount St. Helens proved geologists can still be surprised by nature. Its run-out landslide, a Sturzstrom, reached USGS volcanologist David Johnson at what was thought a safe observation point, 10 km away. It is now called “Johnson Ridge”.
I think we are in for a surprise at Bardarbunga-Askja. The ratio of (length of the rift extension (as illustrated by the earthquake map) to the depth to mantle could be at a scientifically observed high. I could be wrong about that, hence my earlier question about longest recorded fissure. Maybe it will erupt at only one place. Maybe at two ends. Maybe not at all — that would be a surprise!
But remember the solid basalt is more dense than the lava. If an eruption “unzips” the rift along a 50+km length, an unhealthy amount of crustal sag could manifest; the cold rocks “sinking” under the extruded hot lava. A positive feedback in a long fissure eruption: the more lava ejected, the greater weight that must be held up by crustal stiffness. It will push the crust down more, ejecting more lava. It would vastly increase the volumes possible for eruption. The great flood basalts in geologic history were probably a manifestation of repeated eruptions along long fissures with positive feedback. Of course, Iceland itself is one of these great flood basalts.
“…It will push the crust down more, ejecting more lava. …”
If it erupts on top = no change … or very little.
The ‘limit’ to magma production is related to asthenosphere pressure drop and catchment area. areas by square of radius and volume by cube. So larger area dramatically increased potential non-linearly. The width of deep extension and surface rend is the control on production, and that won’t be known until it’s almost over.
Do you know what is the depth of the Moho here is & what the depth of the brittle-ductile transition in the crust is here – just curious as it relates to earthquakes, especially the brittle-ductile transition ( ie is is at the 12 km depth we are seeing most the quakes – if yes, there may be more deformation deeper that is aseismic.
Moho is around 39 km for one source I looked at some days back, another said 46 km, another said 29 km, and some other persons said these are all about right as it varies, and the Moho under the major fissure swarms is around 20 km.
Most of the crust be below Vatnajökull is thicker, ~15 to 16 km. One look at the terrain becomes clear why, and I don’t mean ice. Many quakes have been occurring below 12 km, people are just ignoring them for the most part. And there are several under the fissures to as much as 25 to 30 km lately.
But the best evidence is to just look at the outcrop and terrains as to what goes on there.
Although I haven’t seen research to confirm this , I suspect the brittle-ductile transition zone here would would be shallower than normal due to high high flow. See :
http://en.wikipedia.org/wiki/Brittle–ductile_transition_zone
Thus the reason the majority of seismicity is above 12km. Could just mean deeper deformation is occurring but is aseismic.
has it started? is that what I’m seeing on the web cam?
http://baering.github.io/
Yup.
Cool….nothing saying it has a the IMO though.
I see that they are calling it a fissure eruption north of Dynjujokull
From: mbl.is
A fissure has started north of Dyngjujökull, in Holuhraun. …..
The crater is believed to be a 1 kilometer long rift bearing NA-SV. No jökulhlaup has been detected; the eruption is not sub-glacial.
At the moment the fissure is estimated to be around 100 meters long. ….
An eruption started in Holuhraun north of Dyngjujökull at around 00:02. Seismic tremor was observed on all seismic stations and the web camera installed in the area by Mila has showed some nice pictures of the eruption. It is a small fissure eruption and at 02:40 AM the activity appears to have decreased.
What Will Become Of Bárðarbunga?
James Ashworth 8/29/14
Past 5 hours: 2 quakes at Mag 4.8 and 5.2 under Bardarbunga
5 quakes between Mag 2.6-3.3 under the active part of the rift.
1 quake near Askja in the high 2’s.