A magnitude 5.7 earthquake hit Iceland's Bardarbunga volcano this week, the biggest since tremors started over a week ago.
There is still no sign of an eruption however, according to the country's Meteorological Office.
Intense seismic activity at Iceland's largest volcano system has raised worries that an eruption could cause another ash cloud like that from the Eyjafjallajokull volcano in 2010. The incident shut down most of Europe's airspace for almost a week.
"There was one event during the night, it was a magnitude 5.7 (quake), the largest in this series," Palmi Erlendsson, a geologist at the Met Office said, according to Reuters. "Activity is still deep and we see no signs of anything close to the surface."
On Aug. 24, Iceland lowered its warning code for possible volcanic disruption to the aviation industry to orange from red, the highest level on the country's five-point alert system, after determining that seismic activity hadn't led to volcanic eruption under the glacier.
Red alert means an eruption is imminent or underway, with a significant emission of ash "likely' according to Reuters.
Met Office scientists believe the earthquakes are a result of magma flowing out from under the crater of the volcano, which causes a change in pressure.
The migration of magma, estimated at around 10.6 billion cubic feet, along a 21 mile dyke by Icelandic scientists on Aug. 25 could stop.
This should lead to a gradual reduction in seismic activity, according to the Met Office.
The magma could also reach the surface away from the glacier however. This would lead to an eruption, but with limited explosive, ash-producing activity, according to the scientists.
If the magma reaches the surface under the glacier, that would cause flooding and possibly an explosive eruption and ash production. An eruption inside the Bardarbunga caldera is also possible, though experts say it is less likely than other scenarios.
"We still can't say whether it will cease, continue like this for a while or erupt. It's impossible to say," Erlendsson said, according to Reuters.
Locations around the volcano, in the center of the North Atlantic island nation, have all been evacuated.
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