Geophysicist Einar Kjartansson at the Icelandic Meteorological Office believes that a small eruption occurred in the volcano Katla in south Iceland last summer when the glacial river Múlakvísl from the Mýrdalsjökull icecap, which covers the volcano, flooded.

The flood in Múlakvísl. Courtesy of ICE-SAR.

In the case of glacial outbursts from calderas in glaciers, geothermal heat melts glacial ice. The meltwater accumulates and then bursts forth from underneath the icecap with great force. This usually results in depression of a large area  of the glacier’s surface, ruv.is reports.

After the flood in Múlakvísl, which tore a hole in the Ring Road, there were depressions in four areas on Mýrdalsjökull with an additional depression in the center of the graben which formed very quickly.

It is a phenomenon not seen by the Metrological Office’s geophysicists before. “It is an indication of a very rapid melt underneath the icecap [...] and it is hard to see how that could have happened without a small volcanic eruption occurring there,” Kjartansson said.

Further supporting the theory was the seismic activity picked up by sensors on the day of the flood, which was of a comparable level as usually measured in volcanic eruptions. It was of a higher magnitude than the seismic activity measured during the eruption on Fimmvörduháls in 2010.

“It is another indication that magma came in contact with the ice below the glacier,” Kjartansson explained. He added that the small eruption hasn’t necessarily reduced tension below the glacier nor decreased the likelihood of a larger eruption.

Katla is currently under close observation.

ESA