IMO reported that the cone just E of Sundhnúk and along the fissure within the Reykanes volcanic system continued to erupt lava. The average effusion rate was 0.9 (± 0.4) cubic meters per second during 15-25 April, whereas during the first half of April the rate was an estimated 3-4 cubic meters per second. By 25 April the lava-flow field was an estimated 6.16 square kilometers with an approximate volume of 34 (± 1.9) million cubic meters. The average thickness of the flows was 5.5 (± 0.3) m.

During 24-30 April lava flowed S through an open channel near the cone and, more distally, through lava tubes. The tubes transported lava to the area NE of Grindavík, inflating the flow field along the constructed barriers there; on 27 April a small flow overtopped the barrier and flowed down to its base. Gas emissions continued to drift downwind and residents were advised to monitor air quality. Inflation from magma accumulation beneath Svartsengi was first detected at the beginning of April and has continued based on modeling of GPS and satellite data, though on 30 April IMO noted that the rate had slowed during the previous few days.

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)