September 1, 2014

expert reaction to seismic activity in Bárðarbunga volcano

Further reaction to activity in the Icelandic volcano.

Prof David Rothery, Professor of Planetary Geosciences at The Open University, said:

“The eruption of Bardarbunga / Holuhraun that began in the early hours of Sunday has now been continuous for more than 24 hours. It is a fissure eruption emitting basalt lava, which has a low gas content and has a sufficiently low viscosity to allow such gas as it has to gather into large bubbles that burst at the surface, rather than expanding inside the volcanic plumbing with sufficient violence to shatter the magma into ash fragments. Instead, we get lava flows that spread out across the ground on either side of the fissure.

“This eruption seems to be similar to the shorter-lived one that occurred two days previously (Friday 29 Aug) and is occurring along a longer length of the same fissure. These fissures are essentially a consequence of the rifting of the north Atlantic ocean, which is widening at an average rate of a few centimetres per year. The current short-term rate of spreading north of Bardarbunga is higher than that, because that’s just how rock fractures. Strain is built up gradually and stored elastically, until a rupture breaks open and allows the stress to be relieved.

“This kind of eruption is not a hazard to aviation, unless something changes drastically. There could still be a major ash-producing if the current basaltic magma mixes with chemically different (more silica-rich), gas-rich magma below Bardarrbunga (to the SW) or Askja (to the N). However, as has been said many times, there are several reasons why such an event would not cause disruption on the scale of the 2010 Eyjafjallajokull eruption: it would need to be strongly explosive, the high-altitude wind would need to be in an unfavourable direction, and the rules on how much ash can be tolerated by jet engines have been relaxed.

“A similar fissure eruption at Krafla in 1984 lasted a fortnight, whereas a 1980 eruption lasted seven months.”

Declared interests

None declared