The recent volcano eruptions in Iceland have created enormous circular depressions in two of the country’s glaciers. These dramatic features, which differ from each other in their origins and shape, are visible from the air.
A reconnaissance flight over Bárðarbunga, the volcano where the first earthquakes were detected last month, shows that the ice over the caldera has fallen nearly 20 meters across an area about 7 kilometers long and 5 kilometers wide. This is a change in volume of 250 million cubic meters. The scientists at the University of Iceland attribute this shift to a movement of the base of the glacier rather than to melting. Magma has drained from a chamber under the glacier as it moves to the northeast and erupts onto the surface. As the chamber has emptied, the rock above it has shifted downward, carrying the glacier ice downward as well. This is the largest subsidence that has been observed in Iceland since measurements of the surface were begun over fifty years ago. This movement does not seem to be associated with geothermal activity at Bárðarbunga, or of a higher likelihood of an eruption there. A recent photo from a helicopter flight shows the large extent and relative shallowness of this cauldron (the technical term for these craters).
Another flight travelled over Dyngjujokull Glacier, to the northeast of Bárðarbunga. It showed two separate depressions, somewhat smaller in extent, but almost twice as deep, reaching down 35 meters. These are probably associated with small eruptions of lava below the surface of the ice. Such eruptions can cause the formation of cauldrons like these, without unleashing outburst floods. There is some risk of continued eruptions, including larger ones, at this site.
In recent days, the lava eruptions from the main fissure have been moving in two directions. The main flow from the eruptions is traveling to the northeast. It has recently reached the Jökulsá á Fjöllum River, releasing large quantities of steam. As this intrusion of lava into the river continues, explosive releases of gasses could occur, or a dam could be formed by the cooled lava, creating a lake and subsequent floods. A smaller branch of the fissure has opened close to Dyngjujokull. Should another branch open up a few kilometers to the south, under the glacier itself, there might be a flood or an explosive release of large quantities of ash. For the time being, though, the threat level remains at orange.
The eruption and steam have created hazy skies over the area. The Icelandic Civil Protection Authority has issued alerts to people downwind of the eruption with respiratory conditions, since there are elevated concentrations of sulfur dioxide. They continue to monitor the entire region carefully.
The Icelandic Met Office announced that an eruption began at midnight, local time, at Holuhraun, north of Dyngjujökull. Lava is emerging on the surface, rather than beneath a glacier, so it is directly visible.
The lava is being emitted from a fissure about 900 meters long, with what the Civil Protection Authority calls “low lava fountains with thin flowing lava.” The lack of ash means that the risk to aviation at present is small. Had the eruption occurred under the ice, there would have been a much larger risk of an ash cloud like the one in 2010 that halted air traffic for six days.
The Icelandic Met Service had briefly raised the warning level at Bárðarbunga to red, but after a few hours brought it back to orange. There is a small area restricted to aviation, but it does not extend even to the regional airport at Akureyri in the north.
A webcam from the area at Bárðarbunga does not show much activity, though last night the eruption from Dyngjujökull could be seen in the distance.
Authorities are continuing to order an evacuation area north of the glacier. The possibility of an outburst flood cannot entirely be ruled out, even though the magma has moved north of the country’s major glaciers to areas of bare rock.
Though we don’t have many dramatic photos to show at this point, we would like to share a cartoon that appeared yesterday, just before the eruption started. It comes from a producer of children’s music, who lives on a new volcanic island near the main island of Iceland. You can follow her on twitter at @islandofelska.
And we would like to send our thanks to Gísli Pálsson, who sent us an email this morning from Reykjavik to alert us about the eruption. You can read his account of a recent visit to a glacier in a non-volcanic part of Iceland here.
Our Icelandic colleagues have just contacted us. Ásdís Jónsdóttir writes “Just a note to tell you that an eruption has begun in Vatnajökull – it is under the outlet of Dyngjujökull. It started about half an hour ago (at quarter past two p.m.). They are evacuating areas to the north of the glacier (they were partly evacuated earlier).” Gísli Pálsson adds “ It’s now maximum alert, limited air travel around.”
The Icelandic Meteorological Office ha upgraded the aviation alert to red: “Eruption is imminent or in progress – significant emission of ash into atmosphere likely.”
Their most recent report indicates that lava has emerged under the glacier, but that the future progress of this event is still unknown: They list six points (From http://en.vedur.is/earthquakes-and-volcanism/articles/nr/2947)
A small lava-eruption has been detected under the Dyngjujökull glacier.
The Icelandic Coast Guard airplane TF-SIF is flying over the area with representatives from the Civil Protection and experts from the Icelandic Met Office and the Institute of Earth Sciences. Data from the equipment on board is expected later today.
Data from radars and web-cameras is being received, showing no signs of changes at the surface.
The estimate is that 150-400 meters of ice is above the area.
The aviation color code for the Bárðarbunga volcano has been changed from orange to red.
Some minutes ago (14:04), an earthquake occurred, estimated 4.5 in magnitude.