Friday, September 12, 2014

Bárðarbunga Volcano Disrupting Other Volcanoes?

Tungnafellsjökull volcano rumbles, Askja volcano quakes, and Herðubreið shakes. What is going on in Iceland? Bárðarbunga's new activity and magma intrusion does indeed seem to be 'squeezing' neighboring volcanoes into a state of higher seismicity. To the West of the Bárðarbunga caldera lies a Pliestocene-Holocene volcano called Tungnafellsjökull, which contains a large caldera, and shield volcano. It has no record of activity during human occupation of Iceland, and it's uncertain whether it has erupted in the last 8,000 years.

Askja volcano, to the North, and neighboring Herðubreið volcano, a Tuya, are also experiencing heightened quake activity. Askja is responsible for one of Iceland's largest eruptions in historical time, which created a caldera (which is now filled by a lake), and fissure eruptions on its flanks. Herðubreið has not erupted in historical time, yet now there appears to be persistent seismic disturbances happening beneath its summit.

So what could be happening? Well, a few things really, but none of them appear to be precursors to imminent eruption... yet...

Tungnafellsjökull is characterized by the Smithsonian GVP:

"The Tungnafellsjökull central volcano, located immediately NW of the massive Vatnajökull icecap, contains two calderas. One is largely filled by the Tungnafellsjökull glacier, and the other ice-free caldera located to the SE contains Pleistocene rhyolitic lavas. The 1535-m-high Tungnafellsjökull volcano is largely of Pleistocene age, but postglacial flank fissures on the NE side have produced young basalts. The Hágöngur central volcano to the SW is part of the Tungnafellsjökull volcanic system."

Earthqauke activity at Tungnafellsjökull has picked up since the dike intrusions, eruptions, and unrest at Bárðarbunga, leading some to believe that it could be 'reactivated' as a result of the crustal pressures. Indeed, magma can remain hot and ready in a volcanic system for a long time, slowly cooling into what's known as 'crystal mush'. In this state, the magma is more viscous and thick, and not typically ready to erupt unless it gets new magma injection... but what happens when a magma chamber gets 'squeezed', as I suspect is happening. Does it build pressure, causing rock fracture, and possible unrest? I see this scenario as most likely... but so far there has not been any opinions generated by Iceland volcanologists (they tend to shy away from 'opinion' and rely on data).

When a large rush of magma from what is probably the main magma plume in Iceland starts moving mountains, you can bet there will be some activity in other parts. Whether or not this generates eruptions in other volcanoes around Bárðarbunga is anyone's guess right now. Typically volcanoes require fresh magma and immense pressure to erupt, but I've never seen an eruption quite like the one in Bárðarbunga, with such rapid ascent of magma dikes and sustained lava flow. Only Kilauea tends to erupt this way, and like Iceland, its volcanic system is attributed to a magma plume or hot spot. The difference is Iceland's hot spot sits on the mid oceanic spreading ridge between the North American and European plates, which spread apart, making eruptions in Iceland potentially more drastic.

In any case, the situation in Iceland is highly dynamic at this point. Good place to keep your eye on for now.

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