8 PHOTOS Iceland volcano See Gallery Earthquakes over 5 magnitude shake Iceland volcano Our pilot made an extra circle around #Bardarbunga this morning to let passengers check it out. Thanks to Erla Vinsý! http://t.co/7JUerxD0tE REYKJAVIK, ICELAND - NOVEMBER 08: Towering ash plume from Iceland's Eyjafjallajokull crater during it's eruption, spewing tephra and cloud of ashes that drift toward continental Europe on May 10 2010 near Reykjavik, Iceland. (Photo by Etienne De Malglaive/Getty Images) RT @TIME: See close-ups of a volcanic eruption in Iceland Photo: Ragnar Th. Sigurdsson—Arctic Images http://t.co/vlMw15zQeT http://t.co/PS9… Iceland reopens airspace after lowering the threat alert on Bardarbunga Volcano from red to orange. On August 31st lava began to spew from Iceland’s second tallest mountain, Bardarbunga, with fountains of molten rock reaching heights of over 160 feet. The alert warning for the area surrounding Iceland's Bardarbunga volcano was kept at orange on Tuesday, indicating increased unrest with greater potential for an eruption. Smoke is spewing from the volcano, and lava is spouting nearby. (Sept. 2) Iceland issues a red alert to the aviation industry for the Bardarbunga volcano, meaning significant ash emissions are likely. This picture taken on August 23, 2014 shows scientists to fixing and updating Seismometer and communication equipment that broke down the other day over Bardarbunga volcano, Iceland. Iceland lowered its alert over the nation's largest volcanic system to orange on Sunday after keeping it for one day at the maximum level amid fears of an imminent eruption. AFP PHOTO / Arni Saeberg / ICELAND OUT (Photo credit should read ARNI SAEBERG/AFP/Getty Images) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

REYKJAVIK, Iceland (AP) - Two earthquakes measuring over 5 in magnitude - the biggest yet - shook Iceland's Bardarbunga volcano Sunday after the country issued an aviation red alert warning that an ash-emitting eruption may be imminent.

Iceland's Meteorological Office recorded earthquakes of 5.3 and 5.1 in the early hours. It said there were no signs of an eruption.

The volcano, underneath Iceland's vast Vatnajokull glacier, has been rattled by thousands of small earthquakes over the past week.



On Saturday scientists reported a small eruption under the ice, but it was not visible on the surface, and the Met Office later said it appeared to have stopped. On Saturday scientists reported a small eruption under the ice, but it was not visible on the surface, and the Met Office later said it appeared to have stopped.

Authorities have declared a no-fly zone of 100 nautical miles by 140 nautical miles (185 kilometers by 260 kilometers) around the epicenter as a precaution.

A 2010 eruption of Iceland's Eyjafjallajokul volcano caused a week of international aviation chaos, with more than 100,000 flights cancelled. Aviation officials closed Europe's air space for five days out of fear that volcanic ash could harm jet engines.

Any new eruption is likely to be less disruptive. European aviation authorities have changed their policy, giving airlines detailed information about the location and density of ash clouds but leaving decisions to airlines and national regulators.

Britain's National Air Traffic Service said it was monitoring what it called a "dynamic situation" but was expecting normal operations Sunday.

The agency said it was using alternative flight paths across the Atlantic as a precaution.

Virgin Atlantic said a London-to-San Francisco flight took a slight detour Saturday to avoid Iceland's no-fly zone.