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Calamità » Vulcanico - Approfondimenti, 20 Marzo 2017 alle 15:25:21

New study estimates frequency of volcanic eruptions

UNIVERSITY OF LEEDS

Holidaymakers concerned about fresh volcanic eruptions causing flight-disrupting ash clouds might be reassured by a study setting out the first reliable estimates of their frequency. While the University of Leeds-led research suggests that ash clouds are more common over northern Europe than previously thought, it puts the average gap between them at about 44 years.




It also reveals that these types of ash clouds have about a 20 per cent chance of occurring in northern Europe in any one decade.


Lead author Dr Liz Watson, from the School of Geography at Leeds, said: “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.”


The work began soon after 2010’s explosive eruption of Icelandic volcano Eyjafjallajökull, which caused more than 10 million air passengers to be stranded and cost the European economy an estimated £4 billion.


A team of researchers, which included academics from the universities of St Andrews and South Florida, compared records of volcanic ash fallout (also known as tephra) during the last 1,000 years.


Focusing on northern Europe, which is downwind of Iceland, one of the world’s most active volcanic regions, they examined samples taken from peatlands and lake beds in mainland northern Europe, Great Britain, Ireland and the Faroe Islands, alongside previously existing samples taken from other sites across northern Europe.


The samples – cores up to seven metres long – were taken from peat and lake sediment where geological records are particularly well preserved.


Using electron microscopy and chemical analysis, the team identified tiny shards of preserved volcanic ash, called cryptotephra - about the width of a human hair - which enabled them to pinpoint at what point volcanic ash clouds had spread across the continent.


For many of the occurrences, the researchers were also able to match sample data to historical records or to existing geological data which charted specific eruptions.


The work found evidence of 84 ash clouds during the last 7,000 years, most of which could be traced to eruptions from Icelandic volcanoes.


More incidences of volcanic ash are recorded over the past 1,000 years, because evidence is better preserved and historical records are more complete, leading the team to estimate an average recurrence of 44 years.



 


ARTICOLO COMPLETO: http://www.leeds.ac.uk/news/article/3964/new_study_estimates_frequency_of_volcanic_eruptions

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