Every now and then we are reminded that Iceland really is the Land of Fire and Ice. These days, the largest glacier in Europe*, Vatnajökull (Glacier of Lakes), is announcing that it actually hides beneath it part of one of the most impressive volcanic systems in Europe, if not the world. One of Earth’s most powerful volcanoes covered by one of Europe’s largest glaciers is the perfect depiction of the extremes that Iceland is famous for. (*by volume)
The roughly 3,000km3 glacier blankets a small part of a huge volcanic system with a diverse range of volcanoes, and Bárðarbunga (Bardarbunga or Bart’s bump) is but one of them. This roughly 2,000 metre-tall stratovolcano under the glacier is part of the 200 kilometre-long volcanic system that sits along the border of the eastern and northern volcanic rift zone, where the North American Plate meets the Eurasian Plate.
The two tectonic plates drift apart over a mantle plume, meaning magma flows in to fill the expanding rift. To give some idea of the potential lurking in this volcanic hot spot beneath all that ice, remember that this volcano once produced the largest lava flow ever known over the past 10,000 years, some 8,600 years ago. That eruption resulted in a nearly 30km3 lava field that covered about 950km2.
Historically, there have been large eruptions at Bárðarbunga every 250 to 600 years, but the last major activity was between 1701 and 1864, or 150 to 300 years ago. Seismic activity has been steadily increasing since 2007, and Bárðarbunga started to rumble again in August. During that time, some 20,000 earthquakes have occurred. Most have been below magnitude 3, but more than 200 have gone over 3, and some had topped magnitude 5 by mid-September.
The seismic activity continues, and the whole Bárðarbunga caldera has been sinking. Scientists are not sure why but the physical movement of the 10 kilometre wide, and 700 metre deep caldera is a sure sign of massive volcanic activity underneath it. The molten lava, however, has actually been escaping to the surface at the Holuhraun fissure, which is located a few kilometres north of the glacier.
This eruption may be draining magma from under the Bárðarbunga caldera, causing it sink. The centre crater at Holuhraun, called Baugur, has been responsible for most of the erupting lava, and it has been slowly forming a new caldera. The eruptive activity there is decreasing and some speculate that it might end within days.
This, however, does not signal the end of the show, by any means. In fact, local scientists predict that a new eruption will commence within days or weeks, but it is impossible to say anything for sure. The driving force is the activity under Bárðarbunga, so as long as it continues, the closing of the Holuhraun fissure just builds up pressure which will have to find its way out in new fissures somewhere along the 200 kilometre ridge, or worst of all, at the Bárðarbunga caldera itself. A sub-glacial eruption could bring devastating floods of epic proportions, so the authorities remain on high alert.