IMO - Icelandic Meteorological Office

11/18/2021 | News release | Distributed by Public on 11/18/2021 09:10

Update on Fagradalsfjall


Since 18th of September no eruptive activity has been observed at Fagradalsfjall, but there are still small quantities of gas measured in the atmosphere. During the eruption​ al deflation signal was detected around Fagradalsfjall, most likely due to magma withdrawal from a deep reservoir which was feeding the eruption.

However, since the end of September, inflation has been detected on Reykjanes Peninsula (following the end of eruptive activity). The signal has been identified on both GNSS and InSAR observations and broadly correlates to the area that was deflating throughout the eruption. The most likely cause of the current inflation is renewed magma inflow at depth.

It is possible that the earthquake swarm that started in late September south of Keilir could be related to the inflow of new magma, although no deformation was detected at the surface during this time.

It is not uncommon that magma inflow occurs immediately following an eruption. The current inflation does not necessarily mean that a new eruption is imminent; this may take years or even decades to transpire, so only time will tell what will happen next at Reykjanes peninsula.

IMO will continue to closely monitor the area around Fagradalsfjall.

The figure shows a time series plot for the GNSS station FAFC close to Fagradalsfjall (see location on the InSAR figure above). from middle of April until middle of August the east and vertical components show slight westward and downward movements. The north component is showing slight southward movement. during August we observe a reduction in this trend and it has turned around in the later part of September. Comparable signal is observed on most GNSS stations in Reykjanses signifying a co-eruptive deflation which gradually turns to inflation as the eruption decreases and stops at the end of September.