| By JENNA GOTTLIEB and JILL LAWLESS Associated Press | Aug 23, 2014, 10:56 AM |
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.
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.
Bardarbunga: Aviation alert downgraded
All earthquakes since August 16. The ones from today are in red. (source: IMO)
The Icelancid Met Office has downgraded the aviation alert for Bardarbunga, from red to orange, meaning that eruption is not imminent. Subglacial eruption is not thought to have occurred yesterday. Seismic activity is still strong and the dyke intrusion in Dyngjujokull has propagated to the north.
Icelandic Met Office (IMO) said this around 12.00 GMT, after a meeting with scientists and the Civil Protection Agency. The aviation alert was raised yesterday to red, but has now been downgraded to orange. Observations show that a sub-glacial eruption did not take place yesterday as previously thought and the low-frequency seismic signal observed has other explanations.
The dyke intrusion under Dyngjujokull, north and east of the Bardarbunga caldera has however been propagating to the north, and is now believed to be about 30 kilometers long. A 4.2 earthquake was detected there this morning, along with numerous other quakes. Since midnight, more then 700 quakes have been detected in the area. IMO says no indication that the seismic activity is slowing down; therefore an eruption can not be excluded.
Two strong earthquakes occured in the Bardarbunga caldera last night and this morning (Magnitude 5,3 and 4.6). These quakes are associcated with pressure changes in the magma chamber beneath the caldera as magma flows out to the intrusion.
The Civil Protection Agency (CPA) declared an emergency phase yesterday and extended the restricted area north of Vatnajokull. CPA will reassess the situation later today.
IMO´s announcement:
Factsheet for NW-Vatnajökull 24.08.2014 11:40 UTC
- Earthquake activity in NW-Vatnajökull is still very strong, 700 earthquakes have been observed since midnight and they are somewhat larger than previous days.
- Two large earthquakes, over 5 where in the Bárðarbunga caldera this night.
- The activity under Dyngjujökull has propagated northwards and is now mostly under the edge of the glacier, where an earthquake of size 4,2 was recorded this morning.
- The dyke under Dyngjujökull is now estimated to be approximately 30 km long.
- There are no indications that the activity is slowing down, and therefore an eruption can not be excluded.
- Observations show that a sub-glacial eruption did not occur yesterday. The intense low-frequency seismic signal observed yesterday has therefore other explanations.
- The Icelandic Meteorological Office has decided to move the aviation color-code from red to orange.
This story, by the Icelandic National Broadcasting Service (RUV), was updated on 24 August 2014, at 12.40 GMT.
http://www.ruv.is/frett/bardarbunga-aviation-alert-downgraded
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