REYKJAVIK An Icelandic volcano that is spewing ash into the air and wreaking havoc on flights across Europe appeared to be easing up on Saturday but could continue to erupt for days or even months to come, officials said.
Iceland's Meteorological Office said the volcano's cloud of black and brown ash had shrunk to a height of 5 to 8 kilometers (3.125 to 5 miles) from 6 to 11 km (3.75 to 6.875 miles) when it started erupting earlier this week.
The volume of magma under the volcano also appeared to be decreasing and the volcano looked less volatile on Saturday as heavy pulsing and violent explosions turned to steadier eruptions.
"There are signs that the pressure is decreasing and that the eruption will be calmer," said Armann Hoskuldsson, a vulcanologist at the University of Iceland.
Still, large parts of Europe enforced no-fly rulings for a third day on Saturday as the plume floated through the upper atmosphere, carrying tiny particles of glass and pulverized rock that could pose dangers for jet engines and airframes.
The eruption is taking place under Iceland's Eyjafjallajokull glacier, normally a popular hiking ground about 120 km (75 miles) southeast of the capital Reykjavik.
Bergthora Thorbjarnardottir, a geophysicist at the Meteorological Office, said the steady eruptions did not necessarily mean the volcano was subsiding.
"The eruption could go on like that for a long time," she said. "Every volcano is different and we don't have much experience with this one -- it's been 200 years since it erupted last."
"We have to watch it carefully because they all behave differently. The last time it erupted it was off and on for over a year."
Icelandic police banned all access to the glacier and the foothills in the area as well as a 1-km radius around the eruption site and said considerable ash fall had been reported in areas around the volcano.
According to geologists with Iceland's Civil Protection and Emergency Management department of the State Police, a massive cloud of ash engulfed the surrounding countryside, limiting visibility to just a few meters in parts of the sparsely populated area.
The volcano is expected to cause further flooding in the area as it melts more of the ice on the glacier.
The Red Cross has opened mass care centers for residents in affected areas and advised people to use masks and protective goggles.
Other parts of the country, including Reykjavik, were unaffected. Flights to and from the country are limited, but flights from the United States are operating regular schedules.
Authorities say ash may fall on Iceland's Westmann Islands off the south coast, which is no stranger to volcanic activity.
In 1973, a long dormant volcano on the main island erupted, forcing the evacuation of its 5,000 inhabitants as a blanket of ash covered the town. Its residents returned only later that year when eruptions finally stopped.
Iceland sits on a volcanic hotspot in the Mid-Atlantic Ridge and has relatively frequent eruptions, though most occur in sparsely populated areas and pose little danger to people or property. The last eruption took place in 2004.