Iceland's volcanic eruption was still causing strong tremors on Thursday, though far less ash and smoke was pouring out into the air.
Huge ash clouds spewed from the volcano last week and led to European air traffic being grounded for days. The smoke and fumes coming from the volcano have much less ash now and the plume has stayed at low levels.
However, the tremors coming from it are stronger now than when the ash plume was at its highest, at about 9 km (5.6 miles), said meteorological office geophysicist Steinunn Jakobsdottir.
"We don't know exactly what this is telling us. This is kind of telling me that it is not stopping yet ... As it looks now it could go on for a while," she told a news conference.
Seismologist Bryndis Brandsdottir said the tremors could indicate a build up of lava, or molten rock, within the crater.
"The lava cannot really go anywhere. It is not flowing out of the crater, it must be accumulating there," she told Reuters.
She said that if did find its way out of the crater then it would probably flow down the north side of the mountain, which is where floods occurred at the start of the eruption last week. This was mostly away from inhabited places, she said.
Another scientist said it was difficult to predict.
"The spectrum of possibilities is very wide. Volcanoes are very different from each other," said Giuliano Panza, a professor of seismology at the University of Trieste in Italy.
He said studying volcanoes was like trying to understand a human heartbeat -- changes in rhythm might mean a problem for one patient but not for another.
The volcano under the Eyjafjallajokull glacier, about 120 km (75 miles) southeast of the capital Reykjavik, has been erupting for 8 days.
"Only the northernmost fissure is erupting now and the plume is occasionally reaching a height of 3 km (1.9 miles), but it is mostly below that," Jakobsdottir said. "It (the plume) is kind of stable at a height of 2 to 3 km," she added.
For locals, ash was set to continue to fall in areas close to the volcano, raising concerns about dangers to livestock from high levels of fluoride in the ash.
Apart from the current volcano, Icelanders have also been warily eyeing the nearby Katla volcano, which is much larger and has a much greater potential for devastation.
It last blew in 1918, flooding huge areas.
Experts say history shows that an eruption at Katla often, but not always, follows one under the Eyjafjallajokull glacier.
ReutersLast Mod: 22 Nisan 2010, 16:12