Iceland’s Reykjanes Volcanoes Could Erupt For Decades, Maybe Even Centuries

The ongoing eruptions on the Reykjanes Peninsula have forced authorities to declare a state of emergency repeatedly, and based on new data, it seems possible that volcanic activity will continue for years to decades and possibly centuries.

This Reykjanes Peninsula is home to 70 percent of the country’s population with the largest city of Reykjavik — also Iceland’s capital — located on the southern shores. It hosts important cultural sites, infrastructure — including the country’s only international airport -— and industrial areas, including several power plants that supply hot water and electricity. The most recent eruption from May through June triggered the evacuation of residents and visitors from the Blue Lagoon, an artificial lake feed by a geothermal power and popular tourist attraction, for the third time in more than two months.

Although the Reykjanes Peninsula hosts a series of volcanoes that have been periodically active over the last 4,000 years, they have been dormant for over 800 years. So the first eruption in March 2021 came as something of a surprise, quickly attracting scientists and tourists. Since then eight eruptions of varying intensity have occurred on the Reykjanes Peninsula, with lava spewing out of fissures and slowly making its way to the coastal town of Grindavík.

An international team of scientists — including researchers from the University of Oregon, Uppsala University in Sweden, University of Iceland, Czech Academy of Sciences and University of California, San Diego — has been watching the volcanoes over the past three years. Analyzing seismic imaging and the composition of lava samples, they’ve uncovered parts of the geological processes behind the new volcanic activity.

Almost all of Iceland’s island is built from lava, says Ilya Bindeman, a volcanologist and earth sciences professor at the University of Oregon. The country sits on the Mid-Atlantic Ridge, the tectonic plate boundary that causes North America and Eurasia to push further apart. Additionally a large plume of hot rocks rising from earth’s mantle is located exactly beneath the island.

Although scientists know the deep origin of Reykjanes Peninsula’s current eruptions, the kind of superficial magma storage and plumbing systems that feed them are poorly known, so Bindeman. The peninsula consists of eight volcanically active sites, so understanding whether there is one shared magma source or multiple independent ones and their depth can help predict the duration and impact of these eruptions.

Analyzing samples of lava rock from two different eruption sites, their similar chemical fingerprints implied a shared magma storage zone below the peninsula. Imaging of Earth’s interior based on earthquake waves also suggests the existence of a single 10-kilometer-wide magma chamber about 9 to 11 kilometers in Earth’s crust. Based on seismic activity records covering the area, the researchers estimate that fresh magma was injected in this chamber sometime between 2002 to 2020.

However, this temporary storage is ultimately fed by pulses of melting rocks deeper in the mantle — a virtually inexhaustible reservoir — which can cause eruptions that last decades, Bindeman explains.

Although this marks the beginning of potentially persistent volcanic episodes in Iceland, the researchers can’t precisely predict yet how long the episodes and the gaps between each will last.

“Nature is never regular,” so Bindeman. “We don’t know how long and how frequently it will continue for the next ten or even hundred years. A pattern will emerge, but nature always has exceptions and irregularities.”

The last time a volcano erupted on the Reykjanes Peninsula the volcanic activity continued for over 30 years.

Iceland’s volcanic activity is less volatile and explosive than eruptions in other countries, and so far, the advancing lava buried only pastures, damaging roads and power lines. In May 2024 over 3,000 residents of Grindavik and nearby settlements were evacuated for a month as one of the most powerful eruptions to date started. An advancing lava flow is almost impossible to stop if not the supply at the source — the volcanic vent — is cut off.

“When you witness a volcanic eruption, you can feel that these are the massive forces of nature, and you yourself are very small. These events are ordinary on the geological scale, but on the human scale, they can be devastating,” Bindeman concludes.

The full research paper “The Fagradalsfjall and Sundhnúkur Fires of 2021-2024: a single magma reservoir under the Reykjanes Peninsula, Iceland?” was published in the journal Terra Nova and can be found online here.

Additional material and interviews provided by the University of Oregon.