Bárðarbunga volcano – experts respond

Locals and holidaymakers have been evacuated from areas near the Icelandic volcano Bárðarbunga, which has been threatening to erupt for the last few days.

Iceland volcano
Credit: Tristan Ferne (Flickr)

Although Bárðarbunga (Bardarbunga) isn’t spewing magma or ash yet, scientists are concerned about what Iceland’s Meteorological Office describes as an ‘intense seismic swarm’, where they recorded some 2,600 earthquakes over the weekend and detected the strongest earthquake since 1996 on Monday morning. Previously, this activity has caused some volcanoes to erupt.

However, if Bárðarbunga does erupt, experts are in debate about whether the effects will be as bad as the smaller volcano Eyjafjallajökull in 2010. Because volcanic ash can severely damage jet engines, Eyjafjallajokull’s massive ash plume caused major air traffic disruption for several days, leaving millions of passengers stranded globally.

The following is a response from New Zealand-based vulcanologist Dr. Sigrún Hreinsdóttir at GNS Science, who is currently monitoring the volcano’s activity in real-time.

From your understanding of the situation so far, is an eruption likely?

“It is really hard to predict if it will erupt or not, but that really depends on the magma availability. Currently we are seeing a dike intrusion forming at 5-10 km depth. A magma chamber at around 6 km depth is deflating, pushing magma into the fissure swarm. Right now the activity is staying at ‘safe’ depths. We should see shallowing of earthquakes prior to an eruption.

“We can not rule out an eruption while the seismic activity is going strong and the area around the volcano has been evacuated just in case. However the dike is moving further and further away from the centre of the volcano and the main magma source and we see no progression upward, making it less likely that it will end up in an eruption. Again, this will depend on how much magma had accumulated in the magma chamber prior to this activity. The volcano’s activity is being monitored closely.”

Could you briefly describe what kind of volcano Bárðarbunga is and how an eruption would look? Would a large ash cloud similar to Eyjafjallajökull be expected? 

“Bárðarbunga is Iceland’s ‘queen’ volcano – one of the biggest in Iceland. It is located under the Vatnajokull ice cap and is presumably located on the top of the Iceland mantle plume. It has a big caldera and fissures trending north-east and south-west from the centre of the volcano, and the total length of the system is 190 km. The caldera is about 700 metres deep and 80 square kilometres (10 km diameter). The volcano is also one of Iceland’s most active volcanoes and it has erupted 27 times in the last 1100 years (historic times in Iceland), all but four being under the glacier.

“Due to the location of the central volcano beneath the Vatnajokull ice cap and the fissure swarm extending outside the ice cap, the range of eruption style could vary. The thickness of the ice is in some places 850 metres thick. Fissure eruptions outside the ice cap would be like the Krafla fires. The more common eruptions,  fissure eruptions under the ice cap, would melt the ice, cause flooding and then the ice-magma interaction would cause an explosive eruption similar to the Gjalp eruption in 1996.

“The magma type is not as fine-grained as Eyjafjallajökull ash, so it would be similar to the 2011 Grímsvötn eruption. The 2011 eruption caused temporary airspace closure in Europe but even though the ash plume went a lot higher, it did not cause as much trouble since heavier ash doesn’t travel as far.”

Is the underlying geology similar to New Zealand, or are the two countries volcanically active for different reasons? 

“Iceland is located at a mid-ocean ridge where two plates are moving apart and it owes its existence above sea level to a mantle plume.  This is very different from the settings New Zealand as here two plates are moving towards each other. However, the Taupo Volcanic Zone is resulting from rifting so there are similarities and rifting episodes in Iceland and TVZ have things in common.  What makes the volcanic activity in Iceland so problematic is that many volcanic centres are located beneath ice caps.  Magma and water interaction leads to explosive eruptions.”

For more background information, see comments from New Zealand experts on 2011’s Chilean volcanic eruption and commentary here on the Eyjafjallajokull eruption in 2010.

In addition, our colleagues at the UK SMC have collected the following expert commentary. Feel free to use these quotes in your reporting. If you would like to contact a New Zealand expert, please contact the SMC (04 499 5476; smc@sciencemediacentre.co.nz).

David Rothery, Professor of Planetary Geosciences at the Open University, comments:

“The earthquake locations under the ice at Bárðarbunga migrated northeastwards overnight. It is possible that a fissure eruption will begin either below the ice or perhaps beyond the edge of the icecap. Any eruption is not likely to produce a high ash column, because Icelandic magma does not usually contain enough gas to drive a powerful explosive jet. But until erupted samples are available for analysis we can’t rule out the possibility that magma has been stored and fractionated long enough to become gas-rich, as was the case in the 2010 eruption of Eyjafjallajokull. Meltwater from the icecap could also mix with the magma to cause explosions.

“If any eruption does produce a high column of fine ash, it would be a significant problem for UK and trans-Atlantic air traffic only if the wind carried it southeast, which today’s winds would actually do. However, whereas in 2010 aviation protocol was not to fly through air where ANY ash was present, the rules have been changed to allow flying though ash provided that it does not exceed 4 microgrammes per cubic metre. It is challenging to measure ash density with high confidence, but even so a repeat of the 2010 Eyjafjallajokull today would lead to a smaller volume of airspace being closed to traffic.

“The most likely hazard if an eruption occurs is flooding when subglacial meltwater escapes, and the Icelandic authorities have already closed access to vulnerable areas.

“If a fissure eruption occurs beyond the icecap, it could be very impressive – perhaps a 100 metre high fire-fountain along a 1 km fissure, feeding lava flows. I am looking forward to seeing video if this happens.”

Dr Nicolas Bellouin, an expert on atmospheric dust clouds at the University of Reading, comments:

“Volcanic ash is made of tiny pieces of sand and minerals, blasted out from an erupting volcano, which are then suspended in the atmosphere and transported by winds. Where the ash goes is dependent on the direction of the wind. If winds continue to blow from Iceland to the UK, as they are at the moment, ash from an eruption will be transported to the UK and northern Europe.

“Volcanic ash is a hazard to aircraft, because of sandblasting of the outside of the plane and because particles are sucked into the turbines where they can melt and disable the engines.For that reason, aviation authorities impose a limit on the maximum concentration of ash aircraft can fly through. In the UK, the current limit is 4 mg per cubic metre.

“Detection of volcanic ash plumes is primarily based on satellite and ground-based instruments. Satellites give a picture of the extent of the plume, but are less useful to work out how high or low the plume is in the atmosphere. Ground-based instruments, such as lidars — lasers shot vertically into the sky — are able to give the altitude of the plume, and an estimate of its concentration, over the locations where they are installed.

“Numerical models, which simulate the dispersion of the ash plume with winds and its removal from the atmosphere, are used to forecast the location and extent of the plume.

“Following the eruption in Iceland in April 2010, the Met Office, which is one of nine Volcanic Ash Advisory Centres around the world, deployed a permanent network of lidars to cover the British Isles, and also has a dedicated research aircraft which can fly through plumes to take measurements. The Met Office dispersion model, called NAME (Numerical Atmospheric-dispersion Modelling Environment), has also been improved. This should provide a better picture and forecast of where any future volcanic ash plume exists, and where it is headed.

“People with health conditions affected by pollution should not be overly worried, and a plume of dust is unlikely to have much effect on our weather or climate. Compared to local sources of pollution, such as dust particles from car exhausts, the impact of the volcanic ash is limited, because it tends to exist mainly high in the atmosphere and is not around long enough to cause problems.”

Professor Giles Harrison, an atmospheric physicist at the University of Reading, comments:

“During the eruptions of the Eyjafjallajökull and Grímsvötn volcanoes in Iceland in 2010 and 2011, the UK government asked the University of Reading’s Department of Meteorology to work with the Met Office on measuring and modelling the dust cloud, which closed UK airspace for several days.

“Since then, Reading scientists have been working with the Icelandic Met Office to test new sensors for weather balloons, aimed at measuring volcanic plumes emitted near to their source in Iceland. These instruments could provide a new source of information for calculations predicting the spread of a plume, and have been developed from our previous balloon measurements during the Icelandic eruptions of 2010 and 2011. This work contributes to a more sophisticated system for detecting and predicting how any future volcanic eruption could affect aviation, particularly for the UK.”

Dr Dave McGarvie, Senior Lecturer in Volcanology at the Open University comments:

“We’ve known for some time that Bárðarbunga was going to do something – we just didn’t know what. Now she has stirred, she is giving us clues about what she is going to do. The clues from the pattern of earthquakes show that seismic energy is being expended in two main clusters – one to the North East on the glacier margin, and one to the East under the ice. Adding in the clues from the pattern of earth movements indicates that magma is moving towards the surface, and if it gets there it will erupt.

“The good news for air travel is that both these clusters are away from the heart of the main volcano, as it’s in the heart that the kind of magma is produced which leads to highly explosive eruptions that produce the abundant fine ash capable of being transported long distances through the atmosphere. Current indications are that if an eruption happens it will produce modest amounts of denser ash and only cause local disruption to air travel. But we know so little about this volcano that she could surprise us.”