The flow of magma into a 15-kilometre-long crack before recent volcanic eruptions in Iceland occurred at the highest rate observed anywhere in the world for this type of event.
“We can have higher rates in very large eruptions,” says Freysteinn Sigmundsson of the University of Iceland in Reykjavik. “But I don’t know of higher estimates of magma flowing into a crack on the surface.”
Sigmundsson is part of a team that has been using ground-based sensors and satellites to monitor recent volcanic activity beneath Iceland’s Reykjanes Peninsula. This began with the accumulation of magma several kilometers beneath the Svartsengi region, the site of a geothermal power plant that supplies hot water to the Blue Lagoon spa, a tourist attraction.
On November 10, 2023, a huge crack several kilometers deep and 15 kilometers long formed nearby. As it opened, some of the accumulated magma flowed toward it at a speed of 7,400 cubic meters per second, the team calculated.
This is about a hundred times faster than the magma flow that occurred during the 2021, 2022 and 2023 eruptions in the nearby Fagradalsfjall area, says Sigmundsson.
The magma in the crack can be visualized like a piece of paper, since it is a maximum of 8 meters wide. The crack formed because Iceland is located at a boundary where tectonic plates are moving apart.
On December 18, a fissure eruption began in part of this accident and lasted three days. Another, which lasted two days, began on January 14 and some of the lava reached the evacuated town of Grindavik.
While the lava flows have consumed only a few buildings, cracks in the ground have caused extensive damage to roads and pipes, and have also created underground cavities, Sigmundsson says.
On February 8, another eruption began a little further from Grindavik. The resulting lava flowed through pipes carrying hot water from the Svartsengi geothermal plant. This means that in some nearby regions heating has been cut off: most buildings in Iceland rely on geothermal water for heating.