Bárðarbunga is expanding, and that means two things. This may be due to magma accumulation and a bulge in preparation for the next eruption. There is also the option that the volcano is recovering from the Holuhraun eruption. Geophysicist Páll Einarsson believes that the major earthquakes yesterday evening were most likely caused by landslides. He says the pressure dropped enough for the volcano to attract magma.
According to the Icelandic Meteorological Office, two major earthquakes with magnitude 3.9 and 4.5 took place yesterday evening in Bárðarbunga. However, preliminary measurements showed that they were smaller than the data of the US geological agency.
Páll says it’s not easy to reconcile these two theories about Bárðarbungi’s behavior, but if it’s preparing for an eruption, earthquakes are a sign of it. However, the eruption is not expected tomorrow or the day after.
Seismic activity at this site decreased after the end of the Holuhraun eruption in 2015, increased again for a while, but decreased somewhat in recent years. Grímsvötn and Öræfajökull are also closely monitored, which Páll believes is now the most urgent task.