Overview of the shallow magma reservoir, conduit properties and effusion style throughout the 2021 eruption near Fagradalsfjall, Iceland

The 2021 Geldingadalir eruption is the first of four eruption events that have taken place since volcanic activity resumed on the Reykjanes Peninsula, SW Iceland, after an 871-year repose. It lasted from 19 March to 18 September 2021 and featured (i) continuous effusion, (ii) episodic effusion on a minute scale, and (iii) episodic effusion on an hour to day scale. The eruption transitioned between these states several times, making it the most diverse eruption on record. We provide an overview of the eruptive processes during the entire eruption using video camera footage and seismic tremor data.

Our aim is to image the changes in the subsurface structure, to identify the driving processes, and to interpret the dynamics of the volcano. We will present our view on the most striking questions: What triggered the transition between these different states? What do these different effusion states mean in the context of the conduit and the shallow magma reservoir? What can we learn from the tremor amplitude, tremor duration and repose time of such episodic events?