GPS observations and ground deformation maps from Sentinel-1 satellite data show that the Askja volcano began to swell in early August 2021.
The uplift signal is centered on the western edge of Öskjuvatn, near Ólafsgígar, and corresponds to ~5 cm/month of vertical movement. Geodetic modeling (performed using GPS and satellite data) shows that the source of this deformation is at a depth of about 3 km and corresponds to a volume change of about 0.001 km³/month.
The cause of this deformation is unclear, but it is most likely caused by an influx of new magma. Askia volcano is seismically active, and earthquakes occur regularly in this area.