To Flood or Not to Flood?

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To Flood or Not to Flood?

By Rachel Mercer
Jökulsá á Fjöllum bridge

The bridge over Jökulsá á Fjöllum. Photo: Páll Stefánsson.

In the wake of the start of the eruption of Bárðarbunga at the Dyngjujökull glacier, scientists are continuing to consider the possible effects of the event. One of the biggest topics of discussion has been the possibility of the flooding of the glacial river Jökulsá á Fjöllum, which would be caused by the ice cap melting.

The latest update has it that for the past few hours, a 15-mile long dike underneath Dyngjujökull has been rapidly expanding several miles to the north. The expansion of this dike is thought to be due to magma from the volcano that is flowing in a northeasterly direction.

Magnús Tumi Guðmundsson, professor of geophysics at the University of Iceland, anticipates that subglacial eruption could lead to an explosive eruption. In an interview with the DV newspaper, he described the chain of events that might be expected to occur as the volcanic activity continues: “First of all there will be a great deal of melted ice which will lead to a glacial flood. Once the eruption has broken through the ice cap there will be an explosive eruption, in which the volcanic material will separate into small particles that disperse into the atmosphere as fine tephra that can spread very widely.”

However, according to Melissa Anne Pfeffer, a scientist with the Iceland Met Office who specializes in ash dispersion, there is not enough magma yet to melt the ice cap at the site of the eruption, which would be the determining factor in whether or not a flood occurs. The ice cap measures 300 to 1,300 feet in thickness.

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