Tremor pulses detected beneath Mýrdalsjökull glacier

Tremor pulses were detected beneath Mýrdalsjökull glacier on Wednesday, and electrical conductivity in the Múlakvísl river has risen, suggesting that a glacial flood has begun or may be starting, mbl.is reports. However, a natural hazard specialist says there is no indication that a very large flood is imminent.

“It was at around six this morning, around noon and then at about one or two o’clock. There is now a somewhat larger tremor pulse, but it appears to possibly be dying down,” said Jarþrúður Ósk Jóhannesdóttir, a natural hazard specialist at the Icelandic Meteorological Office.

All earthquakes recorded at the volcano on Wednesday were below magnitude 2.

Jarþrúður said floodwater could be passing the monitoring stations and might only become visible on the gauges several hours later, as has happened at a station near the main road.

“Something could be starting to flow at the moment. We do not know exactly what is happening, but we will have a clearer picture in a few hours. It appears to be dying down, and we are of course monitoring the situation closely,” she said.

The tremor pulses recorded in the evening were more intense than the previous ones, but did not indicate that a very large volume of water was moving.

“We are comparing this with an event two years ago and the values recorded then, and this is still relatively calm by comparison,” Jarþrúður said. She added that specialists would remain calm as long as the water level did not rise significantly.

She was referring to a very large glacial flood in the Skálm river east of Mýrdalsjökull in late July 2024. Specialists said at the time that the tremor beneath Mýrdalsjökull showed all the signs of originating from a small eruption beneath the glacier. Earth scientists later repeatedly told Morgunblaðið that they considered a small eruption at Katla, the volcano beneath Mýrdalsjökull, the most likely explanation.

Páll Einarsson, professor emeritus at the University of Iceland’s Department of Earth Sciences, said the flood resembled glacial floods from Katla in 1955, 1999 and 2011.

Katla experienced an intense earthquake swarm during the winter. Volcanologist Ármann Höskuldsson told Morgunblaðið at the time that it would not be unusual for an eruption to follow.

Dozens of earthquakes occurred beneath the glacier during the swarm. The largest measured magnitude 4.4, while four others were above magnitude 3.