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Updated: Tue, 19 Aug 2014 11:47:41 GMT | By CBC News, cbc.ca

Iceland volcano Bardarbunga rumbling threatens air travel

An aerial handout photo from the Icelandic Coast Guard shows a plume of steam rising 22,000 feet (© 6700 meters)

An aerial handout photo from the Icelandic Coast Guard shows a plume of steam rising 22,000 feet (6700 meters) from a crater under about 656 feet (200 metres) of ice at the Eyjafjallajokull glacier in southern Iceland April 14, 2010. The volcanic eruption on Wednesday partially melted a glacier, setting off a major flood that threatened to damage roads and bridges and forcing hundreds to evacuate from a thinly populated area. Picture taken April 14, 2010. REUTERS/Icelandic Coast Guard/Arni Saeberg/Handout (ICELAND - Tags: DISASTER) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS - RTR2CU42 Arni Saeberg/Reuters

The world's airline industry is on alert after Icelandic authorities have raised the alarm over a sudden flurry of small earthquakes that could cause one of the country's largest volcanoes to erupt.

The Icelandic Meteorological Office warned Tuesday it has detected more than 3,000 minor earthquakes since Saturday along a fault line in the country's centre.

Much of the activity is clustered around Bardarbunga — a subglacial stratovolcano under Iceland's largest glacier. "Several of these events were larger than magnitude 3," the office warns, with one touching 4.5 on the Richter scale — the strongest in that region since 1996 — although none has been that strong in the past 24 hours.

Although seismic activity in Iceland is routine, the sudden increase in number and intensity has volcanologists worried, because the last time similar activity was seen was in April 2010, when Eyjafjallajokull erupted and the plume of ash and smoke grounded transatlantic air travel for the better part of a month.

Seismologists say magma is moving horizontally, not yet vertically, and "no signs of migration towards the surface or any other signs of imminent or ongoing volcanic activity have been detected so far."

However, the aviation alert level has been raised to the second-most severe level as a precaution.

"Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood … and ash emission," the office said.

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