Volcano Watch: Recent eruptions in Iceland sparked interest far and wide

by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates

Footage of Iceland’s Fagradalsfjall eruption on Reykjanes Peninsula in 2021 showed glowing lava flows and bubbling cones that were evocative of Hawaiian eruptions. Visitors and reporters flocked to the Iceland eruption site, while scientists and local authorities monitored the eruption closely to keep everyone safe.

The Fagradalsfjall eruption gained such fame that it kept attracting people even after the eruption stopped on Sept. 18, 2021. Last month, on Aug. 3, after almost a year of repose, a new eruption began.

Prior to the recent activity, the last eruptive period in the area was over 800 years ago. Two fissure eruptions from the Krýsuvík-Trölladyngja volcanic system produced extensive lava flows that entered the ocean on the peninsulas north and south coasts. According to the Scientific Advisory Board of the Icelandic Civil Protection, the Reykjanes Peninsula could be entering into a period of extended unrest that could include alternating seismic, deformation, and eruptive activity.

This region is one of the few places where the Mid-Atlantic Ridge is visible on land, with eruptions characterized by effusive lava flows and limited tephra deposits. Iceland’s international airport is located on the western end of Reykjanes Peninsula and the capital, Reykjavík, lies on the northeastern end. Therefore, eruptions on the peninsula have the potential to be highly disruptive.

The current unrest along the Krýsuvík-Trölladyngja volcanic system started in January 2020 around Mount Thorbjorn with seismic activity and uplift that was beyond the typical background levels. Scientists concluded that a magmatic intrusion had occurred at several kilometers depth based on seismic and deformation data. Throughout the year, several more seismic swarms and intrusive episodes occurred in the area, along with a few stronger earthquakes.

In February 2021, increased seismicity and a deformation signal suggested an intrusion occurred near Fagradalsfjall. By early-March, seismic activity ramped up with increased earthquake counts, larger events, and seismic tremor—which was attributed to shallow magma movements at around 1–1.5 km (0.6–1 mi) depth. The Icelandic Meteorological Office noted that an eruption was possible without any strong precursory signals because the magma was already close to the surface.

Around 8:45 p.m. on March 19, 2021, an eruption began near Fagradalsfjall, in Meradalir valley. Low lava fountains erupted from an approximately 200 m (650 ft) long fissure. After several weeks eruptive activity focused at a single vent where the fountains built a horseshoe-shaped spatter cone feeding a channelized lava flow through its opening. 

The eruption site was approximately 10 km (6 mi) from the nearest populated region and about 2.6 km (1.6 mi) from the peninsula’s south coast road—so not in the immediate vicinity of critical infrastructure.  The threat level was considered to be relatively low because of its location, size, and effusive nature.

The eruptive activity lasted for 6 months, and after it ended, inflation suggested that magma was flowing into the area at depth. In late-December 2021, another intrusion and earthquake swarm followed, which appeared similar to the one in March 2020.

On July 30, 2022, increased seismic activity reappeared on Reykjanes. Deformation around Fagradalsfjall suggested that magma from a shallow intrusion was approximately 1 km (0.6 mi) below the ground surface and on August 2 the IMO released a statement saying that an eruption near Fagradalsfjall in the coming days was likely. The following day an eruption began.

Around 1:18 p.m. on Aug. 3, a new fissure opened in Meradalir valley, located on the northern ridge of the March 2021 lava field.  After the eruption onset, seismicity and deformation rates quickly slowed.  Unlike the 2021 eruption, activity decreased significantly after less than three weeks. By the night of Aug. 21, there was no indication of volcanic activity at the eruption site, and the volcanic tremor had ceased.

The IMO continues to monitor the situation closely for any signs of change, along with dozens of other volcanoes in Iceland. Time will tell if the Iceland eruption is over or if it has just entered into a pause. Meanwhile, here in Hawai’i, the eruption of Kīlauea within Halema‘uma‘u continues and will soon reach its one-year anniversary.

Volcano Activity Updates

Kīlauea volcano is erupting. Its USGS Volcano Alert level is at WATCH.    

Over the past week, lava has continued to erupt from the western vent within Halemaʻumaʻu crater. All lava is confined within Halemaʻumaʻu crater in Hawai‘i Volcanoes National Park. Sulfur dioxide emission rates remain elevated and were last measured at approximately 1,400 tonnes per day (t/d) on August 26. Seismicity is elevated but stable, with few earthquakes and ongoing volcanic tremor. Over the past week, summit tiltmeters recorded variable tilt, with less than two microradians of fluctuation.

Mauna Loa is not erupting and remains at Volcano Alert Level ADVISORY. This alert level does not mean that an eruption is imminent or that progression to an eruption from the current level of unrest is certain.    

This past week, about 108 small-magnitude earthquakes were recorded below the summit and upper elevation flanks of Mauna Loa—the majority of these occurred at shallow depths less than 15 kilometers (9 miles) below sea level. Global Positioning System (GPS) measurements show low rates of ground deformation over the past week. Gas concentrations and fumarole temperatures at both the summit and at Sulphur Cone on the Southwest Rift Zone have remained stable over the past week. Webcams show no changes to the landscape.

Three earthquakes were reported felt in the Hawaiian Islands during the past week: a M3.7 earthquake 24 km (14 mi) NE of Honaunau-Napoopoo at -3 km (-2 mi) depth on August 31 at 11:02 p.m. HST, a M3.2 earthquake 11 km (6 mi) ENE of Pāhala at 32 km (20 mi) depth on August 27 at 4:34 p.m. HST, and a M3.3 earthquake 3 km (1 mi) SSW of Pāhala at 33 km (20 mi) depth on August 26 at 6:59 p.m. HST.

HVO continues to closely monitor Kīlauea’s ongoing eruption and Mauna Loa for any signs of increased activity.

Volcano Watch is a weekly article and activity update written by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates.