Volcanologist Haraldur Sigurðsson, who predicted the end of the Holuhraun eruption with remarkable accuracy, wrote on his blog yesterday that there are indications that the caldera of Bárðarbunga volcano, which fed the Holuhraun eruption, has begun rising again.
The rising of the caldera could mean that magma is accumulating in the magma chamber, building pressure, which might eventually lead to another eruption.
“When the subsidence [of the caldera] stopped, the curve of the position of the GPS sensor in Bárðarbunga had become horizontal. In the accompanying graph from the Icelandic Met Office’s website a blue curve shows none or insignificant horizontal movement on the surface of Bárðarbunga from February 7 to March 7,” Haraldur writes.
“I added a red line for comparison [see Haraldur’s blog]. It clearly shows that in the past days, the GPS sensor has started rising again. It can be caused by two things: (A) The ice below the sensor is flowing into the depression … (B) The caldera has started rising again because magma from the mantle is flowing into the magma chamber below Bárðarbunga.”
“I’m inclined to believe the latter explanation, but time will tell. If (B) is correct, it is likely that the flow of magma from the depths into the magma chamber will take many years before it reaches the position which Bárðarbunga had before the eruption which began in 2014,” Haraldur concluded.
Other scientists have predicted that Bárðarbunga will erupt again in the near future and that the eruption in Holuhraun was the first in a series.
The eruption carried on while the caldera subsided and magma flowed out of the magma chamber and into the intrusive dike connecting Bárðarbunga, which lies under Vatnajökull glacier, with Holuhraun north of the glacier.
Using data from a GPS sensor in the caldera, Haraldur and his grandson Gabríel Sölvi calculated the rate of the subsidence and when it would stop, which would mean that magma had stopped flowing into the intrusive dike and hence that the eruption had ended.
They had predicted that this would happen on March 4, while the eruption ended on February 27—they were off by five days.