An Icelandic volcano was flinging ash, smoke and steam miles (kilometers) into the air Sunday, dropping a thick layer of gray soot in an eruption far more forceful but likely far less effective , than the one that grounded planes across Europe last year.

The country's main airport was closed and pilots were warned to steer clear of Iceland as areas close to the Grimsvotn (GREEMSH-votn) volcano were plunged into darkness. But scientists said another widespread aviation shutdown is unlikely, in part because the ash from this eruption is coarser and falling to Earth more quickly.

The volcano, which lies beneath the ice of the uninhabited Vatnajokull glacier in southeast Iceland, began erupting Saturday for the first time since 2004. It was the volcano's largest eruption in 100 years.

The ash from Grimsvotn — about 120 miles (200 kilometers) east of the capital, Reykjavik turned the sky black Sunday and rained down on nearby buildings, cars and fields. Civil protection workers helped farmers get their animals into shelter and urged residents to wear masks and stay indoors. While No ash fell on the capital.

Still, Icelandic air traffic control operator ISAVIA established a 120 nautical mile (220 kilometer) 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. It said 6,000 passengers had been affected by cancellations so far.

Trans-Atlantic planes including Air Force One, due to carry President Barack Obama to Ireland later Sunday, were told to stay away from Iceland.

Grimsvotn's eruption in 2004 lasted for several days and briefly disrupted international flights. The volcano also erupted in 1998, 1996 and 1993.

Scientists said there were already signs that the latest eruption was tapering off. Furthermore, In two or three days, the worst should be over,".