Bardarbunga Volcano Eruption (Months 4-5)

 

Original post; Month 2; and Month 3.
 


 
Resources:

 
 


 
January 21, 2015, 1:45 p.m.: Aviation code: Orange. No change in the eruption, which is pretty amazing. More details in a “month six” post in about a week from now. In the meantime, the lava field looks like a small dot…but a small dot on an island nation is a very big thing.
 

The island of Iceland, with black spot marking the Bardarbunga lava field.  (NASA by way of Erik Klemetti)

The island of Iceland, with black spot marking the Bardarbunga lava field. (NASA by way of Erik Klemetti)

 


 
December 21, 2014, 5:05 p.m. Pacific. Aviation code: Orange. The eruption continues at about the same level as recently. Of note, someone has collected highlights of the many beautiful videos of this eruption (h/t David Bressan/Lorcan Roche Kelly):
 

To most of us, this is just a volcanic eruption, and a very beautiful one. It’s especially important, though, because it is plate tectonics in action. The Earth’s crust is rifting here, just as it is all along the Mid-Atlantic Ridge, which rises above the sea in Iceland. We very rarely have the opportunity to see it in action, as the following video notes. How fortunate we are!
 

 


 
December 18, 2014, 3:07 p.m. Pacific: Aviation code: Orange. The eruption continues, giving scientists a unique opportunity to study how two continents move apart at a plate tectonic spreading center. However, it may be slowing down.

And the University of Iceland has made an amazing discovery:
 

 
(It really does cover about 80 sq km, and is really shaped like that, minus the white trimmings.)


 
December 5, 3:03 p.m. Pacific: Aviation code: Orange. Earlier this week, the scientists went into a little more depth during their discussion that was posted on the UI website. Here is what they said, putting this historic eruption into perspective:

Today the Scientific Advisory Board of the Icelandic Civil Protection reviewed data about the development of events in Bardarbunga and the volcanic eruption in Holuhraun, from the beginning of the unrest until the present day. Most of the data show a decline in the subsidence of the Bardarbunga caldera and the volcanic eruption on Holuhraun. Earthquake activity is though still strong and the flow of lave great in comparison to volcanic eruptions in Iceland for over the last 100 years. The findings of the meetings are as follows:

  • Earthquakes in Bardarbunga: Seismic activity has been very strong since mid-august. The activity peaked in first half of September, it has slowly decreased since then, but activity remains intense. The period of seismic unrest is one of the largest ever recorded in a volcano globally.
  • Earthquakes in the dyke from Bardarbunga to Holuhraun: Strong seismic activity coincided with the progression of the dyke in the second half of August, but it decreased after the volcanic eruption began on Holuhraun. Earthquakes are still detected in the dyke but they are small and relatively few.
  • Subsidence of the Bardarbunga caldera: In the days following the onset of the seismic unrest, the ice-covered base of the caldera began to subsidence up-to 80 cm a day, but the subsidence has since slowed and it is now around 25 cm per day. The subsidence is in the shape of a bowl and it is greatest in the centre of the caldera, about 50 m, but smaller to the edges.
  • Crustal deformation: Extensive ground deformation Major was recorded while the dyke was forming, signalling the progression of the dyke and subsidence towards Bardarbunga. Interpretation of GPS data and analysis of satellite interferograms indicates that the volume of the magma in the dyke is about 0.5 cubic kilometres, and that it was fully formed by the beginning of the volcanic eruption. After the eruption started the subsidence has been steady, but slowly decreasing, towards Bardarbunga.
  • The volcanic eruption in Holuhraun: The volcanic eruption that began on Holuhraun on 31 of August is characterised by a large and unusually steady flow of lava. The magma that comes up is a rather primitive basalt, with a chemical composition typical of the Bardarbunga volcanic system. The petrology analysis of the magma suggests that it stabilised at 9-20 km depth, meaning that it could not have resided at a shallower depth in the crust. The lava field is now 76 square kilometres in area. It is more difficult to measure the volume of the lava than the corresponding area. Measurements by air on 4th and 26th of November indicate that the volume of the lava is now about 1.0 cubic kilometre but the uncertainty is 0.3 cubic kilometres. The flow of lava was about 200 cubic meters per second in September but the average flow rate for November is estimated to have been under 100 cubic meters per second. The new lava field is the largest in Iceland since the Laki eruption (1783-1784) and it is probably the third largest lava field on the planet over that period.
  • Gas: For the first time in 150 years, gas pollution from a volcanic eruption has had an impact in Iceland. The reason is the size and the long duration of the eruption. The flux of the sulphuric dioxide (SO2) in the gas cloud has been measured as high as 1300 kg per second, but the average flux in the first month of the eruption was estimated to have been 400 kg per second. Measurements of the total flux of gas at the eruption site are difficult and the uncertainty of these values are very high. It is probable that the flux of gas will decrease in line with decreasing flow of magma, but this has not been confirmed by measurements. A few cases of high SO2 concentration have been recorded in populated areas over the last few weeks compared to September and October, but in those cases weather conditions may have had an equally large effect as the flux of gas coming from the eruption site.
  • If the unrest continues in a similar fashion, the subsidence of Bardarbunga and the volcanic eruption on Holuhraun will continue for at least some months. The situation could, of course, change so scenerios such a subglacial eruption remain a possibility.
  • Two earthquakes stronger then M5,0 were detected in Bardarbunga from noon on Monday. The former was M5,2 on Monday, 1. December, at 12:52 on the south-eastern rim of the caldera and the second was M5,4 on Tuesday, 2. December, at 02:18 on the northern rim. Since noon on Monday 10 earthquakes between M4,0-5,0 were detected in Bardarbunga and 10 earthquakes between M3,0-4,0. In total about 120 earthquakes were detected in Bardarbunga during that time.
  • Little seismic activity was detected in the dyke and around the eruption site in Holuhraun since Monday.

The same three likely future scenarios of the eruption are discussed.
 

 


 
University of Iceland

University of Iceland

November 29, 2014: Aviation code: Orange. Well we’re going into the fourth month of this eruption. It’s amazing that it has lasted this long without major fluctuations! It is Iceland’s biggest effusive eruption since Laki in 1783, but it is still much smaller than that 18th century catastrophe, fortunately. Basically things are just going on pretty much the same there now.

The lava field now covers some 30 square miles (75 square kilometers). Per Friday’s science meeting,

  • Insubstantial changes have been on the volcanic eruption in Holuhraun over the last two weeks.
  • Seismic activity in Bardarbunga continues to be strong. The biggest earthquake that was detected since noon on Wednesday, was of magnitude M5,1 this morning, 28. November at 06:41. Since noon on Wednesday 7 earthquakes larger then M4,0 were detected in Bardarbunga and 12 earthquakes between M3,0-3,9. In total about 170 earthquakes were detected in Bardarbunga since Wednesday.
    About 20 earthquakes were detected in the dyke and around the eruption site in Holuhraun since Wednesday. All of them were smaller then magnitude M1,0.
  • About 20 earthquakes were detected in Tungnafellsjokull glacier since Wednesday. The biggest one was of magnitude M2,0.
  • Scientists flew over Bardarbunga on Wednesday, 26. November. According to data collected in the flight the total depression of the Bardarbunga caldera is 50 meters [almost 165 feet] and the total volume of the depression about 1,4 cubic kilometre since the seismic activity started in mid-August.
  • No signal is coming from the GPS station in the Bardarbunga caldera, the most likely explanation is that the subsidence of the caldera is so great that the GPS station is now below the caldera rim and is therefore out of sight of the relay station in Kverkfjoll.

The same three scenarios are considered likely, though anything is possible.

  • The eruption on Holuhraun declines gradually and subsidence of the Bardarbunga caldera stops.
  • Large-scale subsidence of the caldera occurs, prolonging or strengthening the eruption on Holuhraun. In this situation, it is likely that the eruptive fissure would lengthen southwards under Dyngjujokull, resulting in a jokulhlaup and an ash-producing eruption. It is also possible that eruptive fissures could develop in another location under the glacier.
  • Large-scale subsidence of the caldera occurs, causing an eruption at the edge of the caldera. Such an eruption would melt large quantities of ice, leading to a major jokulhlaup, accompanied by ash fall.

The Iceland Meteorological Office has this to say today about the subsidence (including caption on graph):

29 November 2014 – how the subsidence is monitored

Until recently, point measurements of the subsidence of the Bárðarbunga caldera were available in near real time as the IMO mounted a GPS station there, 12 September. This station has now subsided so much that it is out of sight of the neccessary relay station in Kverkfjöll and therefore no signal is received.

The subsidence of the Bárðarbunga caldera has also been observed by doing flights along a certain north-south section repeatedly. For convenience, the results are presented schematically, see below. The lower graph has a sixfold exaggeration of the vertical axis and on the upper one the difference in hight is multiplied by a factor of 120. The intention is not to make an image which resembles the volcano but to distinguish clearly and graphically between the results derived after each surveillance flight. Eight flight measurements are shown, from 5 September to 26 November 2014. The Institute of Earth Sciences makes these measurements and interprets the results. A comparison of the black line and the light blue one reveals that the subsidence has not only continued since September but also broadened, affecting a larger area.
 

The rate of subsidence in the centre of the caldera has decreased slowly but the subsided area has also broadened. The change in volume since the last measurement (4 Nov.) corresponds to a magmaflow of 130 m³/s. This is less than the first month, when the estimated flow was close to 200 m³/s. Institute of Earth Sciences, 27 November 2014.

The rate of subsidence in the centre of the caldera has decreased slowly but the subsided area has also broadened. The change in volume since the last measurement (4 Nov.) corresponds to a magmaflow of 130 m³/s. This is less than the first month, when the estimated flow was close to 200 m³/s. Institute of Earth Sciences, 27 November 2014.

Sulfur dioxide still remains a problem, and has occasionally been detected in Europe, too. The fissure eruption is releasing 30,000-40,000 metric tons a day, per the IMO.

The Iceland Review reported this week that new seismic data show that earthquakes (presumably caused by moving magma) underneath the caldera are much closer to the surface than originally suspected, 3 km (about 2 miles) rather than 5-8 km (roughly 3-5 miles). A scientist told reporters the volcano’s magma system is more complicated than they thought. The lava that is being erupted, however, is coming from 9 km (5.5 miles) underground. I’m not sure how the discrepancy is explained.

In a different article, the Iceland Review reports that the eruption has led the government to propose new emergency management laws, to clarify everyone’s responsibility and authority to act, in case there is a subglacial eruption, which could cause major flooding as well as destructive explosive activity.



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