On 22 November the Icelandic Meteorological Office (IMO) lowered the Aviation Color Code for Reykjanes to Yellow (the second level on a four-color scale), noting that seismicity associated with the magmatic dike intrusion had decreased during the previous week. Although inflation continued to be detected at Svartsengi, they determined that the likelihood of an eruption had decreased. During 22-27 November seismic activity was relatively stable at a rate of about 500 earthquakes per day, with most events concentrated near Sýlingarfell and Hagafell. Sometimes around midnight on 27 November an hour-long seismic swarm occurred in the vicinity of Sýlingarfell. A total of 170 earthquakes were recorded and located at depths of 3-5 km; the largest event was an M 3. Seismicity slowly decreased during 28-29 November and most of the events were small, below M 1. The rate of deformation also declined, though uplift at Svartsengi continued at around 1 cm per day. The seismic and deformation data suggested that magma continued to flow into the middle portion of the dike.

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)