British glaciologist Dr Matthew Roberts, who is working at the Icelandic Met Office, says a great deal of ash is being produced because the eruption is taking place beneath the Eyjafjallajoekull icecap. He says: "It's the interaction of the molten rock, the magma, and the glacial ice which is causing the magma to cool very quickly and to be pulverised into tiny fragments of rock.
"And these updrafts of fine volcanic ash are being lifted into the sky by the enormous steam plumes that have been created by the vast quantities of ice that's been melted."
Dr Rothery says various factors may have contributed to the explosive nature of the eruption. The amount of gas - made up of water, vapour, carbon dioxide and sulphur dioxide - in the magma now arriving in the volcano may have become greater than it was in the original batch of magma when it first started erupting in March, and the ice/water from the glacier is being turned into steam when it meets the magma.
The expansion of gas, which is mainly water vapour if it is from magma/ice interaction, drives the ash skywards, and then convection takes over. The plume is warmer than the surrounding air, and so is less dense despite the ash it contains. How high it rises depends on the initial impetus from the expanding gas, plus its heat content. When it reaches neutral buoyancy, it ceases to rise and is then at the mercy of the wind. The newer magma has proved to be higher in silica than that from the earlier stages of the eruption, which means it is more viscous and is more liable to fracture, forming ash. Coarse ash (more than 1mm) falls out, but fine ash (less than 0.1mm) stays airborne for a long time.
The ash has been moving at a height of about 30,000ft due to water going into the vent.
According to Dr Rothery, as Thursday's eruption progressed, the best hope was that the interaction between melt water and the continually arriving magma would lessen. Ideally, solidified magma would isolate the vent from the ice and/or water, so that the eruption would become less explosive, and the plume height would decrease until it was no longer a threat.
However, currently the ash column is higher than it was on Friday. A possible explanation is that fractures caused by magma movement and small earthquakes keep allowing water into the vent, at a sufficient depth that steam expansion has no option but to drive the ash fragments skywards.
When will it stop?
Volcanologists say it is impossible to predict when the eruptions might cease, pointing out that eruptions in Iceland can continue for months.
So, not a lot of good news there then. The disruption could continue for a long time yet. We are already hearing much dissent at the pronouncements of the "experts" who place fly/no ply rules. Oh, and can anyone tell me why the bans run from such precise times? If the ban starts at 1pm and ends at 7pm, would you be happy to be on a 12.55am flight or 7.55pm arrival? The flights continue but it is only Sod's Law that sooner or later one of those jugs will go to the well just one time too many. If there were such a disaster, the no fly periods would have to be extended. Apart from the losses allegedly sustained by the airline companies there is the commercial problem of air transport being shut down.
What to do? I have floated this idea once before but here we go again. The foregoing extracts mention the aerosol effect arising from the pressure underground forcing the ash to a height where it drifts at heights determined to be hazardous for air traffic. Solution to me is to reduce the pressure. The first thought is a massive enlargement of the hole in the Earth's surface that the lava and particles are coming from. I note that America has dispatched a team of nuclear scientists to their major oil leak. I don't really think this is a preface to using some massive device; more ensuring that all possible lines of (innovative) thinking are applied. Well, I may be the equivalent of the Little Dutch Boy (careful with the link - do not go here) but who knows? We do have some incredible powerful explosives outside the nuclear armoury. We have laser-guided aiming and can launch missiles with a very long reach. Maybe we can do little with the actual blow hole - what about breaking up or diverting the flow of the ice and water that is part of the ash-production process? The Icelandic people are well used to living in a country of fire and ice and may well have a fairly relaxed attitude to what is happening over large areas of the world. I have run a moderate-intensity Google over what Iceland might be doing. Sight-seeing trips seems to be the answer. There was some TV coverage that suggested they blame a Goddess deep in the bowels of the Earth who turns over in bed every so often. If I not know already the absolute futility of debating an individual's religious beliefs with them I might have words to say about the restless female theory. Sure as hell, something needs to be done. We are in the 21st Century for God's sake. Even if the counter to the admonition to lie back and enjoy rape were not already out there, it is not a sentiment I would ever support. Come on someone - Have A Go. Please.