SECOND UPDATE: It has been confirmed that Grimsvotn volcano underneath the Vatnajokull glacier in southeast Iceland has begun erupting.
A plume of ash is visible, which has led scientists to confirm earlier reports of an eruption. Vidir Reynisson at the public safety unit of the Icelandic police says it is too early to tell how big an eruption it will be, although it shows signs of being bigger than the last one in 2004.
Earthquake activity began in the area at 18.00 this evening (local time) — which was taken as a clear sign of an imminent eruption. The emergency co-ordination centre at Skogarhlid in Reykjavik is in operation.
Grimsvotn is a large volcano buried under glacial ice. It erupts regularly, the last time in 2004. At the time, aviation was directed away from the ash; but there was no major disruption. Grimsvotn has never caused any major delays or cancellations to international air traffic — unlike the bigger Eyjafjallajokull eruption last year. The 2004 eruption and the one in 1998 both lasted around a week.
Authorities have set up a no fly zone over the volcano this evening. It stretches 120 nautical miles in all directions. There are no delays or cancellations to flights into and out of Iceland and international aviation is easily able to fly around the volcano zone.
A joklahlaup is expected some time tomorrow, whereby the pressure of melted water literally lifts the glacier to release a huge and sudden flood. Such events are usual when Grimsvotn erupts and south Iceland infrastructure is built to cope with it. Road closures are somewhat likely and can be followed on www.vegagerdin.is.
Vegagerdin has already decided to close the Route 1 highway near the glacier in preparation — and because visibility is extremely poor due to the ash. The ash cloud has already risen to some 45,000 feet.
(Photo: Agust Rafnsson, taken at the Fimmvorduhals volcano in 2010)