Q&A: Latest Volcanic Ash Plume

Q&A: Latest volcanic ash plume

Page last updated at 12:04 GMT, Tuesday, 4 May 2010 13:04 UK

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Fresh activity over the weekend resulted in the production of a fresh ash plume

The ash is back. Fresh volcanic activity under the Eyjafjallajokull glacier in Iceland has resulted in a fresh ash plume being pushed about 5.5km (18,000ft) into the air.

Weather conditions had led to a concentrated cloud of ash reaching northern parts of the UK. As a result, aviation authorities banned flights from airports in affected areas on Tuesday morning. Flights in and out of Northern Ireland and the IrishRepublic have now resumed.

Airspace over Europe was closed down for six days last month because of fears of the effect of volcanic ash on aircrafts' engines.

What has caused the latest ash cloud?

The latest plume was the result of a fresh pulse of meltwater and ice from the surrounding glacier entering the volcano, explained Haraldur Olafsson, a professor of atmospheric sciences at the University of Iceland.

Speaking on Tuesday morning, Professor Olafsson said it was similar to the events that generated April's massive ash cloud that spread across much of Europe.

"In the early phase of the eruption, there was a lot of meltwater and ice, which contributed to the explosions, which in turn contributed to a lot of solid material being pushed very far up into the atmosphere."

He added that there was still a lot of meltwater that could cause further plumes to be pushed into the atmosphere.

"It is not finished yet. Sooner or later, this is going to stop, but this is not imminent."

Is it as bad as last time?

Professor Olafsson said the volume of ash being emitted was less than April's eruption, but it still had the potential to cause problems.

Data gathered by Icelandic researchers monitoring the situation showed that the ash cloud was heading south-easterly towards the UK.

"The current plume is very concentrated as the ash is transported towards the British Isles," he told BBC News.

"It is reaching heights of about 5km and is not showing much sign of dispersing."

Aviation authorities took the decision to temporarily ground flights to and from airports in Northern Ireland and the Republic of Ireland as the concentrations of ash exceeding safe levels passed through a part of UK airspace.

Professor Olafsson said that he was aboard a German research aircraft that flew through the plume on Sunday.

"Measurements showed that the most concentrated part of the cloud was only about 100km wide, but it was definitely too concentrated for any aircraft to go into the middle of it."

The ban was lifted at 1300 BST after the concentration of ash was deemed to have dispersed enough to allow flights to resume.

The Civil Aviation Authority (CAA) says that although the flight ban has been lifted, a number of safety measures remained in place, such as inspecting aircraft engines before and after each flight for possible ash damage.

The CAA spokesperson also says that the situation remains under constant review, as the Icelandic volcano is still emitting a plume of volcanic ash.

How long could the current ash cloud cause problems?

It is uncertain at this stage.

"Over the next day or so the weather situation shows winds blowing from the north to north-westerly direction," said John Hammond, a Met Office forecaster.

"This means that areas of ash are expected over parts of the UK, especially western regions," he told BBC News.

"The increase in volcano activity is, so far, not as prolonged as it was last month so the current cloud is not as large at present.

"However, winds blowing from the north to north west have been blowing ash/dust towards the British Isles."

He added that current forecasts suggest that, beyond Wednesday, winds will begin to blow from a north-easterly direction, with the volcanic plume expected to remain to the west of the British Isles.

The latest forecasts and guidance can be found on the Met Office's Volcanic Ash Advisory Centres website .

What is the advice for people planning to travel by air?

"In the first instance, they need to check with their airline for the latest information because the airlines will be fully briefed on the situation," a CAA spokesman said.

The spokesman added that the CAA, along with air traffic control agency Nats, was monitoring the situation very closely and taking advice from the Met Office.

"The forward prognosis of where the ash is heading is still a little bit uncertain, so Nats will publish updated information on any possible further airspace closures."

The spokesman said that lessons had been learned as a result of April's ash cloud, which grounded flights for almost a week.

"We now know a lot more about tolerance levels of volcanic ash in aero-engines," he explained.

"Although there are still no-fly zones of dense ash, we know that in areas of less concentrations, aircraft are safe to fly."