By Robin Wylie |
September 10, 2014
The Bardarbunga eruptive fissure on September 1, 2014. Credit: University of Iceland/Ármann Höskuldsson
The largest lava eruption for over a century is currently underway in central Iceland.
Since August 31, liquid rock has been streaming from a mile-long
fissure in the plains around Bardarbunga, the country’s second highest
volcano. Ármann Höskuldsson, a volcanologist from the University of
Iceland,
says
that the fissure has now spewed more lava, by area, than any eruption
since the 19th century. The university’s most recent estimate puts the
amount of lava at nearly eight square miles — enough to cover a quarter
of the island of Manhattan.
The fissure has been erupting regularly and vigorously since it
opened, shooting lava fountains more than 300ft into the air; the
associated lava flows stretch for up to seven miles.
Contained Risk
Despite its scale, this eruption is not a particularly dangerous one.
Apart from a few intrepid scientists and reporters, the surrounding
area is uninhabited, and consequently the lava poses little threat to
human life.
What’s more, the volcanic ash cloud that was feared by some in the
lead-up to the eruption — because of its potential to damage airplane
engines — has also failed to materialize. (The eruption is currently
emitting only volcanic gas into the air, which does not carry the same
risk to aviation.)
The main reason for the lack of ash is that the eruption is occurring
in an area that is free of ice, the presence of which can cause molten
lava to fragment into minute particles of ash.
But there are signs that that could change.
Warning Signs
On the morning of September 5th, scientists conducting a surveillance
flight above the fissure found that the eruption had spread. A new
fissure had opened, around one mile south of the original (and still
active) one.
Lava emission from this second fissure is ongoing. And, while it is
much smaller and less energetic than its northern sibling, its location
is troubling. The new fissure lies little less than a mile away from a
glacier called Dyngjujökull. The first fissure, by contrast, was around
2.5 miles away. This is a potentially important development because, if
the eruption were to continue to progress like this, it could eventually
reach the glacier — at which point, the likelihood of an ash eruption
would increase dramatically.
Watching the Crater
As yet, there are no signs of that migration. But worryingly, there
is yet another scenario which could produce an ash cloud: an eruption
from Bardarbunga’s crater. So far, the eruption has been confined to the
volcano’s periphery (the two active fissures), with the lava emerging
through unglaciated plains. But the volcano itself lies some 25 miles to
the southwest, below 2500+ feet of ice.
Bardarbunga is buried beneath Vatnajökull, another, much bigger,
glacier. Consequently, if the eruption were to migrate to here, the risk
of ash emission would rise steeply. There are no signs that a crater
eruption is imminent. But something is shifting beneath the ice; the
volcano is being rocked by regular, large earthquakes; and the crater
appears to be subsiding at a rate not seen since records began.
How much ash a subglacial eruption might generate cannot be guessed.
But the infamous eruption of Eyjafjallajökull four years ago — which
forced the biggest closure of European airspace since the Second World
War — is testament to the power of Iceland’s volcanoes
.
For now, Bardarbunga is putting on some great fireworks. But they could pale in comparison to what is lurking beneath the ice.
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