Large Earthquake Shakes Iceland Bardarbunga Volcano Site

A 5.4 magnitude tremor has hit the Bardarbunga volcano early on Saturday, but there were no signs of a fresh eruption.

The quake was recorded at 0703 GMT, said Icelandic Met Office seismologist Martin Hensch.

The latest quake comes a day after a small eruption along a fissure in a glacier about 40km from the main crater in Iceland's largest volcano system.

The Icelandic Met Office had raised its aviation warning to red, its highest level on Friday, then downgraded it to orange. They eventually removed all airspace restrictions after the eruption on Friday ceased.

Authorities have been on high alert since a number of small earthquakes have hit Iceland this month.

Hensch said it was impossible to predict how the situation would develop.

"There are so many parameters in this system," he said. "We cannot make a forecast for the next hours or the next few days. So we have to continue to monitor and react to events when they happen."

Ash cloud fears

The eruption raised concerns because of events in 2010, when Iceland's Eyjafjallajökull volcano erupted and caused a week of international aviation chaos.

Thousands of flights were cancelled when aviation officials closed Europe's air space for five days, fearing that volcanic ash could harm jet engines.

In terms of the environment, in particular, high-fluoride eruptions pose a threat to foraging livestock, especially sheep. In 1783, 79% of Icelandic sheep stock were killed, probably as a result of fluorosis caused by the eruption of Laki.

Large-scale release of sulphur dioxide into the atmosphere also poses a potential health risk, especially to people with pre-existing breathing disorders.

Other notable volcanic eruptions in recent years include the eruption in 1991 of Mount Pinatubo in the Philippines. This eruption lasted eight days, from 7-15 June of that year, with an ash cloud required many days to dissipate.

It resulted in worldwide abnormal weather and decrease in global temperature over the next few years. However, the second phase of Eyjafjallajökull's eruption lasted longer than that of Mount Pinatubo.