The volcano Eyjafjallajökull became famous after April 2010, when it erupted over several months, blanketing northern Europe in vast ash clouds. Flights were halted across the continent for nearly a week as a result of fears that airborne material would prove hazardous for aircraft. Across Europe, the skies fell quiet as the usual buzzing of aircraft overhead vanished.
‘In 2010, when Eyjafjallajökull erupted, people were really shocked – it seemed to come completely out of the blue,’ says Dr Graeme Swindles, Associate Professor of Earth System Dynamics in the School of Geography at Leeds. ‘The last time volcanic ash clouds affected northern Europe before the recent event was in 1947, 70 years ago – but aviation was much less intense at that time and it simply didn’t have the same sort of impact.’
Swindles is co-author of a study conducted by researchers at the University of Leeds in the wake of the Eyjafjallajökull eruption – as well as a smaller, similar incident caused the following year by Grímsvötn, another Icelandic volcano – to determine how frequent these kinds of events are likely to be in the future. The Eyjafjallajökull eruption registered a Volcanic Explosivity Index rating of 4, the level at which ejected volcanic material would begin to interfere with aviation. Could it be that the second half of the 20th century – when the commercial aviation industry had taken off – had conveniently coincided with a remarkable period of low volcanic activity in the region, one which nobody had noticed because it had never been a major issue before?
“Reliable estimates of the frequency of volcanic ash events could help airlines, insurance companies and the travelling public mitigate the economic losses and disruption caused by ash clouds in the future”
‘Although it is possible that ash clouds can occur on an annual basis,’ stresses Swindles, ‘the average return interval for the last 1,000 years is around 44 years. Our research shows that, over thousands of years, these sorts of incidents are not that rare – but people wondering how likely it is that the 2010 chaos will be repeated in the next few years can feel reassured.’
The study reached the 44-year average interval figure – a slightly smaller interval than had previously been believed – by examining new core samples from peatlands and lake beds in mainland northern Europe, the UK, Ireland and the Faroe Islands, as well as existing samples from across the continent, to reconstruct a history of similar volcanic eruptions over the past 7,000 years. By identifying tiny shards of preserved volcanic ash named cryptotephra, they were able to estimate the average frequency of volcanic ash clouds blowing across the continent over the past millennium. Furthermore, they concluded that these types of ash clouds have about a 20 per cent chance of occurring in northern Europe in any one decade.
‘Reliable estimates of the frequency of volcanic ash events could help airlines, insurance companies and the travelling public mitigate the economic losses and disruption caused by ash clouds in the future,’ emphasises lead author Dr Liz Watson, also from the Leeds School of Geography.
This was published in the February 2017 edition of Geographical magazine.