Iceland barely lets a month go by without reminding the world that it’s a song of both ice and fire. Plenty of its volcanoes are considered to be restless to some degree, but one particular hellish hill – Oraefajokull – is currently causing a little concern for volcanologists.
As reported by the Associated Press, the volcano has seen a recent increase in seismic activity. The air smells of sulfur, which is leaking up to the surface along with heated, murky groundwater. A cavity in the snow at the summit is getting deeper at a remarkable rate of 45 centimeters (18 inches) per day.
All signs strongly imply that magma is moving towards the surface.
In the last week alone, Iceland’s Meteorological Office has detected 160 earthquakes in the area, which is a frequency greatly in excess of background levels. As a result, volcanologists are monitoring it intensely, and the alert level has been raised to yellow, which indicates “signs of elevated unrest”.
Oraefajokull is considered to be one of Iceland’s most dangerous volcanoes. It hasn’t erupted since 1727-1728, and a lack of historical data makes it unclear how often it does blow its top. The hope is that it won’t repeat the events of 1362, which were notably violent and which destroyed an entire county through volcanic debris and related flooding.
Dr Tobias Dürig, a volcanologist and postdoctoral researcher at the University of Otago, New Zealand, spent several years researching Icelandic volcanoes on-site. He told IFLScience that, for now, the volcano appears to have calmed down, if temporarily.
“After a period of unrest in September, the seismic activity has decreased,” he explained, before adding: “It hasn't stopped though.”
“This might indicate that something was on the way and has now reached a state of ‘better’ stability.”
This is a common feature of plenty of volcanoes. Magma often rushes up towards the surface, only to stop just short of a conduit. Instead of an eruption, it enters a state of quiescence and pools in a shallower reservoir.
“We cannot exclude the possibility that this state can change, though,” Dürig added.
“There is a possibility that, after a certain stress threshold is exceeded, a batch of magma could be released, which in combination with the overlying glacier could be a hazardous scenario.”
There are two possibilities here, generally speaking, should any erupting lava encounter the Vatnajokull glacier atop the fissure.
The most obvious is that it will produce a sustained column of ash, one that’s continuously fueled by the continued depressurization of the underlying plumbing, along with the release of heat from the rapid quenching of the lava. It could be worse, or not quite as bad, as the scenario brought by Eyjafjallajökull in 2010. Until it actually happens, it’s hard to tell.
Another possibility – one that’s not mutually exclusive to the first – is something called a jokulhlaup. If the heat component of the eruption is high enough, it could cause a catastrophically quick melting of the glacier, which would generate flash floods.
Although it’s somewhat different geologically speaking, the volcano Katla is overlaid by the Myrdalsjokull. Its 2011 paroxysm failed to breach the glacier, but it did trigger a jokulhlaup, one which swept away a major bridge at Mulakvisl – fortunately, without any casualties.
The point is that the same could happen today at any volcano covered by a glacier, Oraefajokull included. At this stage, caution, but not hysteria, is the name of the game.
No-one can say if it will erupt in the near future. “That's why the experts are playing it safe,” Dürig noted.
Researchers are now going to continually measure the ice for any surface changes using state-of-the-art GPS equipment and multiple flights armed with incredibly precise radar. Watch this space.