Saturday, 7 March 2015

The end of volcanic eruption in Holuhraun (Bardarbunga), Iceland

The volcanic eruption in Holuhraun which began on August 31, 2014 came to an end on Friday, February 27, 2015, the Scientific Advisory Board of the Icelandic Civil Protection said on February 28 and confirmed today. The Aviation Color Code for Bardarbunga was downgraded from Orange to Yellow.



Scientists are now analyzing data and examining the eruption site to reassess the hazard assessment.



According to the resolution of a SENTINEL-1 radar image from ESA 27.02.2015, no increase in the extent of the lava has taken place since the middle of February. There are no indications of activity but they'd only be visible on this image if the activity were considerable; therefore this data cannot conclude whether the eruption is over. Credit: nstitute of Earth Sciences.

Seismic activity in Bárðarbunga continues to diminish, the Board said. Only one earthquake stronger than M2.0 was measured since last Saturday (February 28); it was M2.3 yesterday at 04:08 UTC. In total, around 60 earthquakes were detected around the caldera since Saturday.

Around 120 earthquakes were detected in the dyke during the same period. The strongest one was measured M1.6 on Sunday (March 1) at 02:10 UTC. A slightly more activity is now measured in the dyke, which is most likely due to decreased pressure.

Three earthquakes were detected around Tungnafellsjökul glacier, about 30 earthquakes around Herðubreið and 2 in Grímsfjall. All of these earthquakes were weaker than M2.0.

Insubstantial tectonic movements are now detected in the area.

Although the eruption has come to an end, gas contamination is still being detected over and around the lava field and is still expected in the vicinity of the eruption site and the Icelandic Meteorological Office still monitors it closely.

Other lava eruptions have taught that the lava field continues to emit gas for a long time yet and without the thermal rise from an open vent, the volcanic gases will tend to follow the ground.

Therefore, even higher values of more polluting gas may be expected now than in recent weeks.



LANDSAT 8 image from NASA of northwestern Vatnajökull 1 March 2015. Bárðarbunga in the lower left half of the image and Holuhraun in the upper rigth part. Cauldrons and depressions in the glacier are clearly visible and in the lava field slight embers can be seen here and there although the craters seem lifeless. Credit: Institute of Earth Sciences, NASA & USGS. Keep in mind that to the untrained eye, hollows may appear like highs and vice versa.

The lava field is 85 km². Its average thickness is 10 - 14 m (max 40 m) and its volume is 1.4 km³. The maximum subsidence of the caldera is at least 61 m but the rate was only 5 cm/day last week, compared to tens of centimeters earlier. The volume of the subsidence is 1.7 - 1.8 km³.

"Now we have a chance to see how rapidly the volcano is being recharged," Páll Einarsson, a University of Iceland geophysics professor, said for LiveScience. "By monitoring the uplift, we might be able to answer the question: Is this the end of the activity, or do we have to prepare ourselves for the next chapter in the story?"

Einarsson added that predicting Bardarbunga's future based on past eruptions is fraught because each of Iceland's more than 30 volcanoes has its own personality. "We really have to get to know them on a personal basis to tell what they're up to," he said. And Bardarbunga is one of the least understood because it is hidden by a glacier and has a poorly known history.

The Scientific Advisory Board will meet again next Tuesday, March 10, based on that meeting it will be decided if the hazard assessment and the restricted area will be changed.

Featured image credit: IMO

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