European airspace closure justified: vulcanologist
A vulcanologist advising the United Nations said Wednesday that European authorities had no choice but to close much of their airspace last week after a volcanic ash cloud swept in from Iceland.
Henry Gaudru, president of the European Vulcanological Society, said scientists were unable to reliably measure density of ash in the atmosphere except in the more immediate vicinity of an eruption.
Closure to air traffic "was the only measure that could be taken" because there was little knowledge of the exact degree of concentration of ash in the cloud dispersed by winds over Europe and its impact on jet engines, he explained.
"There is at the moment no reliable data on the exact concentration of ash in the atmosphere and when an aircraft can fly, or not, through such plumes," said Gaudru, an expert on volcano monitoring and scientific adviser to the UN International Strategy on Disaster Reduction.
"There have been no studies by aeronautical engineers or meteorologists that could have given indications to civil aviation authorities to assure them that an aircraft would not fall if it flew into the plume," he added.
Gaudru told journalists that the ash spewed to high altitude by Iceland's Eyjafjjoell volcano should die down because water from a glacier that had stoked the plume had evaporated.
But he could not entirely rule out more ash plumes if another breach opened up in the volcano at another location beneath the surrounding glacier, where lava could come into contact with large quantities of water again.
The French vulcanologist emphasised that Eyjafjjoell eruption was relatively small, rating it at about two on the Volcanic Explosive Index, an open-ended measure of eruptions.
The most severe eruptions in history rate six to eight.
However, its impact was amplified by the presence of the glacier that fuelled ash production, the coincidence with prevailing winds that pushed the cloud to mainland Europe and the density of air travel on the continent, he added.
European airspace was reopening again as the eruption declined in intensity on Wednesday, after the volcanic ash shut down flights for days and left thousands of passengers stranded.
© 2010 AFP