The Icelandic Met Office has raised the elevation colour code at Grímsvötn volcano from yellow to orange due to elevated seismic activity at the site. The glacial flood from Grímsvötn reached its peak discharge yesterday morning. Seismic activity at the site has been increasing above the normal level for the past two days or so, and a magnitude 3.5 earthquake occurred at the volcano just after 6:00 AM this morning.
Despite strong earthquakes detected this morning, no volcanic tremor has been detected at Grímsvötn and no increases or changes in geochemical emissions at the volcano have been measured. According to a notice from the Met Office, the seismic activity “is possibly occurring due to the decreased pressure above the volcano, since the flood water left Grímsvötn sub-glacial lake. According to calculations from the Institute of Earth Sciences at the University of Iceland at least 0.8 km3 of water have drained from the sub-glacial lake.”
Grímsvötn volcano is located in the Icelandic highland, underneath Vatnajökull, the country’s largest glacier. It last erupted in 2011 and emitted about 0.8km3 of basaltic tephra. It erupts roughly once every ten years and the eruptions are accompanied by glacial floods such as the one that is currently winding down.
Read more about the glacial outburst flood at Grímsvötn.