ANALYSIS:The volcanic ash cloud may have hit air travel but it is unlikely to have any long-term effects
THE PLUME of volcanic ash now drifting slowly above Ireland, Britain and large parts of northern Europe has effectively shut down air transport.
On the ground, however, it will do little more than deliver a light sprinkling of fine dust.
The wind-blown volcanic ash is not toxic, nor is it likely to have any impact on regional climate.
If the Eyjafjallajökull volcano in Iceland continues to pump out its burden of ash and dust, however, it will continue to play havoc with flights across any air space laden with the stuff.
Unfortunately there is no way to predict the duration of the eruption.
The discharges of magma from Icelandic volcanoes are “sporadic events”, said Prof Alan Jones, head of geophysics at the Dublin Institute for Advanced Studies.
“They can be active for a time and then go quiet for long periods,” he said yesterday. “Generally, these things don’t tend to go on too long before they run out of heat.”
Prof Jones said the eruption was unlikely to cause any long-term effects – other than passenger annoyance – because the size of the volcanic release was not exceptional. “This is not a major volcanic eruption.”
The cloud itself is not ash as from a domestic fireplace. It is fine pulverised stone and minute glass particles, said Dr Quentin Crowley, a lecturer and volcano expert in Trinity College Dublin’s department of geology.
“It is made of very fine particles and this is why they travel so high and so far,” he said.
Toxic gases might be ejected from the volcano, causing a risk much closer to the eruption, but not in Ireland, he said.
The material has been blown out with enough force to drive it to between 6km and 11km into the atmosphere, with most of the particles between 6km and 8km up. This, unfortunately, is the range favoured by modern passenger aircraft.
Iceland has built a tourism industry on the back of its volcanic activity and hot springs.
It has this activity because it happens to sit on a huge split in the Earth’s surface known as the Mid-Atlantic Ridge. It runs from the north Atlantic to the southern ocean, and forms a dividing line between slabs of the earth’s crust that drift in opposite directions, separating at about the speed that a fingernail grows at, Dr Crowley said.
The gap formed provides an escape route for magma and hot gases along the ridge, and Iceland lies along this opening.
Iceland is particularly active, however, because it also sits above a blob of “upwelling mantle”, Dr Crowley said.
The mantle forms part of the Earth’s hot core and in some places it forces a way upwards, getting close enough to the surface to trigger the creation of volcanoes.
This is the case with Iceland, with the mantle melting rocks in the crust that are forced upwards under immense pressure through openings in the Mid-Atlantic Ridge in what is known as a “fissure eruption”.
Aircraft cannot fly through the ash because it can knock out engines.
The very fine particles will already be drifting down lower, and depending on the wind may soon be seen as fine dust on car windscreens and outdoor surfaces, said Dr Kieran Hickey of NUI Galway’s department of geography.
“The original plume material is beginning to disperse,” he said.