More than a year after an Icelandic volcano wreaked havoc for millions of air travelers across the globe, a new eruption has spewed an ash plume 12 miles in the air. Iceland's airports have been shut down, and ash could affect Europe later this week.
Ash could reach northern Scotland by Tuesday and parts of Britain, France and Spain by Thursday or Friday if the eruption continues at the same intensity, airlines were warned on Sunday.
The warning is based on the latest 5-day weather forecasts, but is being treated cautiously because of uncertainties over the way the volcano will behave and interact with the weather.
The Grimsvotn (GREEMSH-votn) volcano, which lies beneath the ice of the uninhabited Vatnajokull glacier in southeast Iceland, began erupting Saturday for the first time since 2004, sending ash, smoke and steam 12 miles into the air.
It was the volcano's largest eruption in 100 years.
The ash from Grimsvotn — about 120 miles east of the capital, Reykjavik — turned the sky black Sunday and rained down on nearby areas, covering buildings, cars and fields in a thick layer of gray soot. Civil protection workers helped farmers get their animals into shelter and urged residents to wear masks and stay indoors. No ash fell on the capital.
The eruption was far larger than last year's eruption at the Eyjafjallajokull (pronounced ay-yah-FYAH-lah-yer-kuhl) volcano 80 miles away, but scientists said it was unlikely to have the same global impact as that one, which left 10 million travelers stranded around the world.
"It is not likely to be anything on the scale that was produced last year when the Eyjafjallajokull volcano erupted," University of Iceland geophysicist Pall Einarsson said. "That was an unusual volcano, an unusual ash size distribution and unusual weather pattern, which all conspired together to make life difficult in Europe."
With winds currently blowing the ash northwards, authorities said there was little risk of any further disruption to European or transatlantic airspace over the next 24 hours.
Still, Icelandic air traffic control operator ISAVIA established a 120 nautical mile no-fly zone around the volcano, closed Keflavik airport, the country's main hub, and canceled all domestic flights. It said Keflavik would stay shut until at least noon Monday, canceling about 40 international flights.
Trans-Atlantic planes — including Air Force One, due to carry President Barack Obama to Ireland later Sunday — were told to steer clear of Iceland.
Where it goes after that depends on the intensity of the eruption and weather patterns.
A Met Office spokeswoman said if the eruption continues at its current rate, "the U.K. could be at risk of seeing some volcanic ash later this week." She spoke on condition of anonymity because she wasn't authorized to be quoted by name.
University of Iceland geophysicist Magnus Tumi Gudmundsson said the Grimsvotn eruption was "much bigger and more intensive" than last year's eruption and 10 times as powerful as Grimsvotn's last explosion in 2004.
"There is a very large area in southeast Iceland where there is almost total darkness and heavy fall of ash," he said. "But it is not spreading nearly as much. The winds are not as strong as they were (last year)."
He said the ash now is coarser than in last year's eruption, falling to the ground more quickly.
In April 2010, the Eyjafjallajokull eruption prompted aviation officials to close Europe's air space for five days out of fear that the ash could harm jet engines. Thousands of flights were grounded, airlines lost millions of dollars and weary travelers slept on airport floors across northern Europe.
Some airline chiefs complained that regulators had overreacted. But a study last month in the Proceedings of the National Academy of Sciences concluded the shutdown had been justified. It said the hard, sharp particles of volcanic ash blasted high into the air could have caused jet engines to fail and sandblasted airplane windows.
Grimsvotn's eruption in 2004 lasted for several days and briefly disrupted international flights. The volcano also erupted in 1998, 1996 and 1993.
Sparsely populated Iceland is one of the world's most geologically unstable countries, sitting astride the Mid-Atlantic Ridge, where the Eurasian and North American continental plates rub up against one another. Frequent earthquakes push magma from deep underground toward the surface, and volcanic eruptions are common. The ground is covered by hardened black lava from past eruptions and steam belches from the earth — harnessed by Icelanders for geothermal power.
Volcanic eruptions in Iceland often spark flash flooding from melting glacier ice but rarely cause deaths. Usually they only have a local impact, but when they do draw the world's attention, it's in a spectacular way.
The 1783 eruption of the Laki volcano spewed a toxic cloud over Europe, killing tens of thousands of people. Crops failed and famine spread.
Scientists said there were already signs that the latest eruption was tapering off.
"The intensity of the eruption has decreased markedly overnight," Matthew Roberts of the Icelandic Meteorological Office told the BBC, saying the ash plume had fallen to about 6 miles high.
Gudmundsson said the duration of the latest eruption would probably be short.
"In two or three days, the worst should be over," he said.
The Associated Press and Reuters contributed to this report.