Photo from the Icelandic Meteorological Office’s webcam in Askja caldera, capturing the southern rim on March 10, 2024.
Seismic Activity Persists in Askja Caldera
On March 25, a notable seismic swarm erupted in the northwestern region of the Askja caldera, with more than 30 earthquakes recorded between 08:00 UTC and noon. The most significant tremor registered a magnitude of 3.5 at a depth of approximately 5 kilometers. In addition, three other quakes were measured with magnitudes ranging between 2.0 and 2.5, while the remainder of the activity consisted of smaller events. Until this recent activity, seismic patterns in Askja had remained consistent over the months, with no significant changes since January 2022 and October 2021 when earthquakes of magnitude above 3.0 were observed.
The accompanying map illustrates the location of the earthquake swarm near the northwestern rim of Askja caldera. The blue boxes indicate the sites of GNSS monitoring instruments.
Following a period of stable ground deformation rates since late summer 2021, recent GNSS data indicated a shift in velocity last autumn, as highlighted in a previous report. However, the latest measurements suggest that the rate of ground deformation has once again increased, albeit still below the levels recorded prior to autumn 2023. Additional data to be collected over the coming days will be crucial in confirming this emerging trend in the deformation process.
The graphs below present data collected from the GNSS station Tanni on the caldera’s northern rim. The upper graph illustrates northward movement, the middle graph depicts eastward movement, and the bottom graph shows vertical changes.
Meanwhile, a satellite image taken on March 19 reveals a winter landscape over Askja Lake, largely frozen with only a couple of familiar geothermal hotspots peeking through the ice. This winter’s icy coverage stands in stark contrast to February of the previous year, when Askja Lake was unexpectedly ice-free for that time of year.
Satellite image from March 19, 2024, depicting winter conditions at Askja, with ice-free patches near well-known geothermal areas on the western shore of the lake.