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USF study: Frequency of volcanic eruptions on rise
[08.23.2011]

TAMPA, Fla. -- Volcanic ash clouds have shut down airports from Northern Europe to Buenos Aires to Sydney in the past two years, disrupting global travel and creating the potential for mid-air disasters.

To determine the future probability of these menacing ash clouds, a team of scientists from the University of South Florida and the United Kingdom recently unearthed microscopic layers of ash from the distant past -- hidden in the bogs of Northern Europe -- shedding new light on the frequency of volcanic eruptions.

Their findings, published this month in the journal Geology, provide a basis for assessing and planning for the risk of future eruptions. The team, from the University of Leeds and the USF Department of Geology, determined the likelihood of volcanic ash impacting Northern Europe is at least 16 percent per decade, a rate based on geologically preserved evidence. Because some eruptions are too small to leave detectable ash deposits -- but still large enough to pose a danger to aircraft -- the actual rate is very likely higher, the researchers determined.

The study is the first comprehensive compilation of sedimentary and historical records of ash-fall events in northern Europe spanning the past 7,000 years. Scientists from USF worked with researchers at the University of Leeds and Queen’s University Belfast in Northern Ireland in analyzing ash layers in peats and lake sediments from northern Europe.

Among its findings, the team reported that Icelandic eruptions -- like the 2010 eruption Eyjafjallajökull in Iceland, which brought European air travel to a week-long standstill, have sent volcanic ash plumes drifting over Europe with increasing frequency in the past 1,500 years.

"Gaining a better understanding of the modern-day impact of volcanic eruptions may ultimately help us ensure that our most cutting-edge technology is less vulnerable against these ancient, geological events," said Chuck Connor, a USF geologist and member of the research team.

As a geological event, the Icelandic eruption was not unprecedented, the scientists found. Their analysis revealed the presence of microscopic layers of Icelandic volcanic ash, also known as tephra. These sedimentary records, together with historical records of Holocene ash falls, demonstrates that Icelandic volcanoes have generated substantial ash clouds that reached northern Europe many times.

The advent of air travel, however, adds a new dimension of complication to the eruptions. The International Air Transport Association estimated that the 2010 Icelandic disruption cost airlines nearly $2 billion, affecting the 29 percent of global aviation and 1.2 million passengers a day.

Volcanic ash can stop a jet turbine by melting onto delicate engine parts, which is bad news at 30,000 feet. On the few occasions that passenger jets have flown into an ash cloud, the jets rapidly lost altitude when their engines halted. Fortunately, pilots so far have managed to land safely. Still, the potential for an air disaster is real and worsened by the fact that volcanic ash clouds are nearly impossible for pilots to spot. Dispersed in the atmosphere, they create a barely detectable haze. Forecasting an ash cloud’s path also has proven difficult, a particularly alarming limitation given that the ash can stay aloft for weeks or longer.

In June, an ash cloud from the Puyehue-Cordón Caulle eruption in Chile circled the Earth twice, closing southern hemisphere airports and delaying travelers for days. Northern Europe has been even harder hit recently.

“While exceptionally rare on the timescales of human experience, our study shows they are commonplace on the scale of geologic time," Connor said. "Geologic investigations give us insight into the tempo of these events.”

The complete paper can be read on the journal’s website.

-USF-



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