Volcanic ash: your questions answered
Updated on 20 April 2010
When will the ash clear? Can planes fly at lower altitudes? Could we limit the spread of ash? Your questions on the volcanic ash answered by the country's top scientists.
What is the best guess for the opening of airspace?
"Regarding the eruption of ash by the volcano, I would guess that would continue until at the least the end of the week. The rest depends on the wind direction and weather patterns."
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University.
"Once the highly explosive activity that is generating the very small particles of ash has ended, then perhaps three or four days. Maybe less if the wind steers the ash cloud past the UK."
Dr Dave McGarvie, Volcanologist, The Open University.
Can planes avoid the ash if they fly at lower altitudes?
"No, for two reasons. First, the ash is descending slowly and records around the UK show that the plume is ubiquitous between 2 -7 km altitude (and occasionally higher in places). Below 2 km the ash is very quickly caught in the turbulence of the surface boundary layer and deposited to ground though jet aircraft are not permitted to fly lower than 2 km due to surface hazards. Second, it is not fuel efficient for aircraft to fly lower than 35,000 ft on long haul flights - for example, aircraft simply could not carry enough fuel for transatlantic flights if they flew at less than 5 km altitude."
Dr Grant Allen, Centre for Atmospheric Science, University of Manchester.
"Planes cannot avoid ash at lower altitudes. It all falls to the earth in the end."
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University.
"No, because the ash is in the lower atmosphere already and slowly drifting down towards the surface. But if we had better ash-detecting radar that could give real-time 3D imaging of the ash cloud, we could perhaps identify low-risk corridors through which aircraft could fly in relative safety. This is not possible at the moment."
Dr Dave McGarvie, Volcanologist, The Open University
"No, a very large proportion of the ash, and much of that very fine, is between the surface and 6,000ft. Typically light aeroplanes fly at 1,000-3,000ft, and airliners at 20,000-40,000ft."
Dr Guy Gratton, Head of the Facility for Airborne Atmospheric Measurements, Cranfield University.
Is the CO2 the volcano is spewing out more or less than the cancelled flights would have produced? (from @asomouk)
"I saw this interesting figure on the internet that may be useful. Details of who produced it are on the figure. It was published on the day of the eruption, but I think it nicely demonstrates that the CO2 emissions of the eruption are small fry compared to the planes!"
Dr Peter Abbott, School of Geography & Geosciences, University of St Andrews
"As Icelandic volcanoes do not erupt much CO2 and there is not much CO2 coming out of this particular volcano. We would need a detailed gas analysis from the eruption site before we could start the number crunching to answer this great question!"
Dr Dave McGarvie, Volcanologist, The Open University
Why has this caused so much grief to Europe when other eruptions in the world don't seem to cause a meltdown? (from @tweetinwayne)
"The eruption is very ordinary and unremarkable. It is the fact that it happens to be combined with local weather systems which push the ash over north European airspace. In other parts of the world ash has certainly interrupted air traffic, for example Ruapehu and New Zealand. In most cases eruptions have not been sustained for long periods and winds have not dispersed them into critical airspaces. Remember that the period of widespread commercial flying is less than 50 years (so we have not yet encountered anything like the diversity of volcanic eruption possibilities that might be produced), and it is only in the last 30 years that we have recognised volcanic ash as a potentially serious threat to aviation. The first international symposium on volcanic ash and aviation safety was in 1991 and there have been several incidents of aircraft flying into ash plumes, for example Indonesia, Aleutians. Thankfully there were no casualties."
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham
How much more/less of the sun's energy is being blocked out by the ash than is normally blocked out by aircraft contrails? (from @ruthie147)
"Aircraft contrails actually warm the Earth's surface, not the other way around. Due to their position in the upper troposphere, contrails act to trap infrared radiation in the lower atmosphere and their net effect over the day/night cycle is to warm the surface. Volcanic ash, however, always acts to cool the surface. Dust and sulphur dioxide which is deposited in the stratosphere reflects solar shortwave radiation to space and also absorbs/scatters it in the stratosphere before it reaches the surface, thus reducing the energy budget at the Earth's surface. Furthermore, ash in the stratosphere does not trap infrared radiation and re-emit it back into the troposphere. In summary, if continued for many weeks, the ash will have a cooling effect on the Northern Hemisphere which would last for many months or even years, similar to the observed effect of the Mt. Pinatubo eruption in 1991 which is documented to have cooled the Earth's climate for several years after the eruption."
Dr Grant Allen, Centre for Atmospheric Science, University of Manchester
"The ash will not be a long term problem - more likely the SO2 which forms aerosols and could block some incident sunlight (but even so this is still a minor eruption and effects will be negligible to now)."
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham
Naive as the question might be, is there anything we could do to limit the spread of ash? (from @SoooooZee)
"Nothing, the main player is the weather system, over which we have no short term control."
Dr Guy Gratton, Head of the Facility for Airborne Atmospheric Measurements, Cranfield University
"Nope. What we could hope for is a way to better track the ash and to determine its density."
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham
Is it safe for my children to play outside? We live in the Northeast of Scotland. (from @Cutty_Darke)
"Yes, definitely."
Dr John Murray, Senior Research Fellow, Dept Earth Sciences, The Open University
"See the links here for health advice."
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham
"At present, the UK CAA trying to understand any potential public health risks. Once we have got samples from the research aircraft, they will be being analysed by an appropriate public health laboratory."
Dr Guy Gratton, Head of the Facility for Airborne Atmospheric Measurements, Cranfield University
Will the ash from Iceland be a recurring problem this year?
"Possibly, but only if a) the volcano continues to erupt and emit ash due to its contact with water and ice; and b) we continue to see high pressure weather regimes over the East Atlantic as we have now, which acts to draw air down from Iceland over the UK."
Dr Grant Allen, Centre for Atmospheric Science, University of Manchester
"Depends if the eruption continues to carry ash upwards with the same intensity. Also depends on the weather bringing the ash down to Europe again."
Prof Jon Davidson, Chair of Earth Sciences, Department of Earth Sciences, University of Durham
"Depends on what happens at the eruption site. The conditions that produced the fine-grained ash that is causing the airspace no-fly problem involve an energetic eruption interacting with ice. This creates steam explosions which in turn fragment the erupting magma into very small particles of ash that can be transported long distances.
Once interactions with ice cease, the steam explosions also stop, as willthe production of the very small particles that is causing the problem. It is normal for eruptions to start energetically and then to become quieter with time, at which point lava flows are effused. So this is likely to happen with this eruption, possibly right now or within a few days.
But - and it is a big but - eruptions like this can have a number of cycles. So we could see another explosive cycle start at any time. Whether this will be as problematic as the current eruption will depend on how energetic the eruption is, the type of magma that erupts and how fast it erupts, and how much interaction there is with ice in the crater.
And of course even if there is another eruptive cycle the winds could steer the ash in a direction away from the UK. Yes, lots of variables. But that is part of the fun and challenge of working on volcanoes."
Dr Dave McGarvie, Volcanologist, The Open University
What if we all just faced the sky and blew? (from comedian David Baddiel @ronskanky)
"It would make no difference because the lower planetary boundary layer is already (a) very turbulent, and (b) where the large proportion of ash is."
Dr Guy Gratton, Head of the Facility for Airborne Atmospheric Measurements, Cranfield University
"You might just get some ash on your face."
Dr Dave McGarvie, Volcanologist, The Open University
