Detailing the magnitude of Icelandic eruption risk is a tricky issue. Even volcanologists admit their helplessness – although Iceland continuously monitors seismic activity in real time. Given a certain level of activity it can take anything from 10s to several decades before the Earth’s crust fractures and millions of tonnes of magma, ash and gas are blasted into the skies.
Reacting to the recent increase in seismic activity beneath Iceland, on 21 August Eurocontrol raised the volcanic ash alert status for European airspace to orange – defined as “heightened or escalating seismic unrest with increased potential of eruption”.
EASA also issued a safety information bulletin detailing the administrative arrangements, communications channels, guidance and regulations applicable to managing an ash event in European airspace. This is a re-statement of the new European system developed as a result of lessons learned during the experience of April 2010 when Eyjafjallajökull erupted and all aviation was grounded for a week.
Theoretically, everyone – airlines, air navigation service providers (ANSP) and national aviation authorities – should already know these things, but the bulletin was sent out anyway as a reminder.
In 2010 it was Eyjafjallajökull that exploded – but when it did, Icelandic volcanologists had been predicting the nearby volcano Katla would erupt.
Katla was then – and remains today – “overdue” for an eruption, according to the historic timetable of its activity. When it does erupt, volcanologists predict, the event will dwarf the Eyjafjallajökull blast.
Right now, however, activity is taking place beneath the Bárðarbunga volcano and the Dyngjujökull glacier, in different parts of Iceland – but it may not break ground there.
Iceland sits on the Mid-Atlantic Ridge, which marks the fault line between two plates of the Earth’s crust – the North American and Eurasian plates. These are moving apart at a rate of a few centimetres a year, and sub-crust seismic activity in Iceland is almost continuous, although the intensity varies.
The Icelandic Metorological Office first put out warnings of extensive seismic activity beneath Bárðarbunga on 16 August.
When an eruption occurs, a variety of factors influence how much impact the event has on commercial air transport. These include the quantity of ash ejected into the atmosphere, how high it is blasted into the sky and the type of ash particles.
If the particles are heavy they fall to earth quickly – if fine, they stay airborne longer and travel further. Both types damage aircraft airframes and engines, but Icelandic ash – especially if the eruption takes place sub-glacially – tends to be fine.
Finally, the direction in which the winds are blowing determines where the volcanic plume and the wider ash cloud travels. If it goes north it affects little-used airspace, but if it heads southeast it threatens to disrupt Europe’s airways once again.