On 18 March IMO raised the Aviation Color Code for Reykjanes to Yellow noting that recent InSAR and GPS data indicated that during the second week of March deformation had restarted. The uplift was concentrated in the same place as that recorded in January-February, though at a slower rate. The cause of the deformation was likely an intrusion of magma at 4.5 km depth.

A large (M 4.6) earthquake was recorded on 12 March and located 3.5 km NE of Thorbjorn, possibly connected to the inflation. A sequence of aftershocks lasted for a few days and was characterized by eight earthquakes over M 3 and about 80 events with magnitudes between 2 and 3. Since the large event a total of 850 earthquakes were recorded in the area.

Geological Summary. The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula.

Source: Icelandic Meteorological Office (IMO)