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Further expert reaction to various aspects of the Icelandic volcano and the effects of volcanic ash.
Dr Michael Branney, Senior Lecturer in Volcanology, University of Leicester, said:
Today’s volcanic eruption in Iceland is not particularly large or unusual: it lies at the lower end of the Volcanic Explosive Index (VEI), a classification of explosive eruptions that runs from 1 to 8, based on the volume of magma that is erupted and the height in the atmosphere that ash plume reaches. By way of comparison, the recent cataclysmic eruption of Mount Pinatubo in 1991 (VEI 6) and the 1980 eruption of Mount St. Helens in USA (VEI 5) were far more explosive. However, today’s widespread impact on aviation caused by this relatively small Icelandic eruption coupled with Northwesterly winds blowing across Europe does serve to remind us of what could happen in the event of a much larger and sustained explosive eruption. We are fortunate that the larger eruptions tend to occur less frequently.
Dr Mike Burton, Senior Volcanologist, Italian National Institute for Geophysics and Volcanology, said:
“I just spoke with my Icelandic colleague. There is some news. The composition of the first sample of ash produced by the summit eruption have been determined, and show that the magma is of andesitic composition, i.e. much richer in silicon than the basalt that was previously erupting in the initial stages. This has two important implications: i. The ash produced will be finer, with smaller particle compared with basalt, even in the absence of water. ii. The activity may well be more explosive than would be the case for a basaltic eruption, due to the higher viscosity of the magma. This is because the higher viscosity magma is more resistant to gas flow, and therefore it’s easier for pressure build up to occur, leading to more violent explosions.”
Prof Malcolm Green, British Lung Foundation spokesperson, said:
“In light of the latest news that ash from the volcanic eruption in Iceland has started to reach ground level in the UK, we would advise people living with a lung condition in affected areas to carry their medication as a precaution as they may experience a short term worsening of symptoms. The British Lung Foundation’s Helpline can also provide advice to anyone concerned about the ash cloud on 08458 50 50 20.”
1. As the ice over the eruption site melts, will that mean that the ash becomes a ‘better sort’ that’s less damaging?
Dr Sue Loughlin, Head of Volcanology, British Geological Survey, said:
“As the ice melts, there will be less availability of water to interact with the magma. This would mean that the eruption would be likely to change from an explosive, ash-producing eruption to eruption of lava flows with small explosions. However, a caveat to this is that we now know that the magma is intermediate in composition – that is, it’s moderately high in silica, so is relatively viscous and may contain dissolved gases. If we start seeing more silica-rich magmas being erupted, then we may see explosive activity continuing because of the presence of gas within the magma. In general, though, it is thought that these silica-rich magmas will only occur in relatively small volumes.”
Dr Michael Branney, Senior Lecturer in Volcanology, University of Leicester, said:
“There is not really a ‘better sort’ of volcanic ash with respect to jet aircraft: any volcanic ash is highly abrasive and also will weld to the insides of the jet engines, but the rate of ash emitted by the volcano may decrease and the height of the ash plume above the volcano may decrease with time.
Meltwater floods around the volcano have been decreasing; there is still lots more ice in the 2.5 km wide caldera-depression at the summit of the volcano. When all the snow and ice around the active fissure is melted and drained, the eruption style could change, for example with quieter eruption or just lava flows rather than exploding so violently as at present. In this case the effects would become much more localised with little widespread impact across northern Europe.”
Dr David Rothery, Dept of Earth & Environmental Sciences, The Open University, said:
“Eruptions usually decline, and I would expect this one to do so, though pulses of renewed vigour cannot be ruled out.”
Dr Clive Oppenheimer, Reader in Volcanology, University of Cambridge, said:
“In some ways yes but overall effects will depend on intensity of the ongoing eruption and wind patterns. When there is a lot of external water around from ice melt explosions are very violent and generate finer fragments of ash. These tend to pick up higher concentrations of fluorine from the emitted volcanic gases, a major concern for farming and agriculture in Iceland. So, the vent “drying out” might reduce these impacts.”
Dr. Thor Thordarson, Volcanologist, University of Edinburgh, said:
“If the vent regions get free of water (which is possible) then the production of fine ash particles will drop significantly (by factor 5-8) and hence less ash will be injected into the higher atmosphere and friendlier the skies will be for the remote regions.”
Dr Mike Burton, Senior Volcanologist, Italian National Institute for Geophysics and Volcanology, said:
“Eventually the ice surrounding the eruption will be melted away and the water created will have been flashed to steam through interaction with the erupting magma. Once the water is exhausted it’s likely that the eruption will be much less efficient in terms of ash production, as was the case in the first phase of the activity between 21st March and 12th April. Therefore, in terms of the impact on air traffic the important question is not only how long the eruption will last, but how long will the ash-producing water-magma interaction continue.”
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University, said:
“Once the ice is melted, then phreatomagmatic activity (explosions caused by steam pressure) will cease, so ash emission is likely to be less strong, though large outbursts may intermittently continue.”
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham, said:
“It’s possible that as the ice melts the vent becomes free of water and ice and the fragmentation efficiency decrease. Then the ash size will be a little coarser (for a given eruption type) and may not get as far up into the atmosphere.”
2. How does anyone judge when it’s safe to fly again?
Chris Yates, Aviation Consultant, said:
Dr Michael Branney, Senior Lecturer in Volcanology, University of Leicester, said:
“The Met Office and NATS will provide information on this. Eventually the ash cloud will dissipate, rendering it harmless. This is being monitored: at the moment, the winds are not dissipating the cloud very rapidly.”
Dr David Rothery, Dept of Earth & Environmental Sciences, The Open University, said:
“When the eruption column height decreases sufficiently, then ash will cease to reach altitudes that are problematic for all except local air traffic.”
“The ash-burden in the cloud can be estimated by remote sensing techniques – such as infrared data from weather satellites and the NERC (I presume NERC) to sample (not sure if they actually sample) or survey the plume with UV and IR”
Dr Clive Oppenheimer, Reader in Volcanology, University of Cambridge, said:
“Excellent question – there has often been talk of what is the safe concentration of ash to fly in but I am unaware of any definitive studies. Another problem encountered is ash on runways – this affects stopping distance and also can do a lot of damage to aircraft as they use reverse thrust and spoilers to slow down.”
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University, said:
“When either the ash from the volcano diminishes, or the airstream changes direction and carries the ash further north.”
Dr. Thurai Rahulan, Lecturer in Aeronautics, University of Salford, said:
“The Met Office does particle count tests to determine the level of contamination at different altitudes and then advise NATS. The dust concentration will reduce but new eruptions cannot be predicted.” (http://www.faam.ac.uk/)
Dr Mike Burton, Senior Volcanologist, Italian National Institute for Geophysics and Volcanology, said:
“Satellite imagery will be the best guide to the mass of ash in play. Images are being continuously collected and analysed by meteorological offices, air traffic control centres and research teams.”
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham, said:
“That’s the job of the national air traffic safety guys – they can monitor the plume by satellite and will want to make sure its dispersed and/or not crossing traffic routes.”
Dr. Thor Thordarson, Volcanologist, University of Edinburgh, said:
“When the volcano stops producing these ash-rich eruptions or the airflow changes.”
3. What are the risks of the eruption triggering the larger Katla volcano?
Dr Sue Loughlin, Head of Volcanology, British Geological Survey, said:
“We know that in the 1820s, the cessation of eruption at Eyjafjallajökull (after 2 years) was followed by the eruption of Katla. However, we don’t know that there was a direct cause and effect. Careful monitoring of Katla is being carried out by authorities in Iceland but we cannot predict whether it will erupt.”
Dr Michael Branney, Senior Lecturer in Volcanology, University of Leicester, said:
“Although there is some risk, there are no signs at present that the large, and potentially more hazardous nearby volcano, Katla, is starting to erupt. However, Icelandic volcanologists will be monitoring this closely. Eyjafjallajökull volcano has erupted so infrequently historically that it is difficult to build up any clear picture of how the two volcanoes might interact.”
Dr David Rothery, Dept of Earth & Environmental Sciences, The Open University, said:
“Small but possible.”
Dr. Thor Thordarson, Volcanologist, University of Edinburgh, said:
“As things stand now – small!”
Dr Clive Oppenheimer, Reader in Volcanology, University of Cambridge, said:
“Low I would think but in general although some “teleconnections” between volcanoes and between eruptions and large earthquakes are recognised, the mechanisms are not well understood. If Katla were more or less ready to erupt anyway, then feasibly earthquake activity associated with Eyjafjallajökull could play a role in triggering an eruption.”
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University, said:
“A huge explosive Katla eruption occurred in 1823, 18 months after Eyjafjoll had started erupting in 1821. This is only one example, and it’s not always safe to assume that a volcano behaves the same way every time it erupts, but the risk is there nonetheless.”
Dr Mike Burton, Senior Volcanologist, Italian National Institute for Geophysics and Volcanology, said:
“The two volcanic centres are 27 km apart, very close indeed. It’s possible that the activity at one volcano can catalyse an eruption at the other, but at the current time no seismic evidence indicates any imminent activity at Katla.”
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham, said:
“Apparently this has happened before;
From Freysteinn Sigmundsson, Volcanological Center, Institute of Earth Sciences, University of Iceland:
“Three previous eruptions of Eyjafjallajökull are known in the last 1100 years (historical time in Iceland). The most recent began in December 1821 and lasted intermittently for more than a year. The neighbouring volcano Katla erupted then on 26 June 1823.”
Dr Colin Macpherson, Department of Earth Sciences, Durham University, said:
“It appears that the last three eruptions of Eyjafjallajökull were followed by eruptions at Katla. This is a recorded fact. At present there is no direct evidence for activity spreading to Katla, but it is something that the Icelandic seismologists will be monitoring carefully.”
4. Have we got any better idea of when the eruption is coming to an end, or what are the signs to look out for?
Dr Sue Loughlin, Head of Volcanology, British Geological Survey, said:
“We can’t predict when the eruption will end. The current phase could last for days or weeks. The eruption as a whole could last for years, with intermittent periods of activity.”
Dr Michael Branney, Senior Lecturer in Volcanology, University of Leicester, said:
“The eruption could continue for several days, weeks or even longer. The last eruption of Eyjafjallajökull, in 1821-3 lasted for over a year; but even if this were to happen again, UK airspace is unlikely to be closed for the duration of the eruption, because the style of the eruption may become less explosive, such that the effects become much more localised, and also because changing wind directions will carry the ash elsewhere.”
“I have not heard any reports of the eruption ending just yet.”
Dr David Rothery, Dept of Earth & Environmental Sciences, The Open University, said:
“Seismicity is low below the volcano (see http://en.vedur.is/earthquakes-and-volcanism/earthquakes/myrdalsjokull ). It was low like this until a few hours before Thursday’s main explosive eruption. If we see several hours of intense seismic activity, it could herald renewed vigour in the eruption.”
“The image shows a v high plume, but is not timed or dated. Matt Roberts quote (http://news.bbc.co.uk/1/hi/uk/8624464.stm) suggests that there is not much ash in the current eruption plume, even if it is high. This would mean that the plume now is mostly just steam, which is good news. It would mean that the ash supply to the plume has been turned off, basically because the eruption is no longer explosive and so no longer shattering magma into ash fragments that can be carried up with the plume. This does not mean that it will not revert to previous behaviour, though personally I would be surprised if that were to happen.”
Dr Clive Oppenheimer, Reader in Volcanology, University of Cambridge, said:
“Not that I am aware of. The Icelandic geophysicists and volcanologists will be in the best position to answer this as they have monitoring data. Some stations will be very hard to access now because of the disruption. There was significant inflation of the volcano in the lead up to the eruption so there is the potential for a substantial volume of molten rock below the summit. The signs of an end will of course include the ash eruption shutting down but then it will be important to continue monitoring earthquake activity, gas emissions and subtle changes in ground height to identify if there is more molten rock left in the plumbing system of the volcano.”
“Just been on phone to my student in Reykjavik… the eruption is ongoing, winds are expected to shift to more northerly later today so they are going to try to get to about 7 km from the volcano for sampling and measurements.”
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University, said:
“The news from Iceland today is that the weather is bad (possible improvement imminent), so the volcanologists cannot see whether the ash is continuing. HOWEVER, volcanic earth tremors are continuing at the same high rate as yesterday, so it seems pretty obvious that ash is still pouring out at the same rate.”
Dr Mike Burton, Senior Volcanologist, Italian National Institute for Geophysics and Volcanology, said:
“A clear indicator will be when seismic tremor is reducing, or if there is a reduction in the pressure of the system, which would be revealed using the GPS network installed around the volcano. Gas flux reductions and gas composition changes may well also indicate an imminent cessation of activity.”
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham, said:
“We would look for geophysical signals (deflation of the ground, reduced seismic tremor, reduced gas emission….) but of course that may simply presage an end to this phase and it could start up again. I don’t think we know when it will “completely” end.”
Dr Colin Macpherson, Department of Earth Sciences, Durham University, said:
“Signs of decreased volcanic activity will be: