The Reykjanes Peninsula, located at the southwestern fringe of Iceland, is among the country’s most densely inhabited areas, and it is equally one of the most geologically active regions. In 2024, advanced sensing technology created at Caltech was utilized in this area to analyze the movement of subsurface magma and its transformation into lava at the surface.
Leveraging information from this technology, known as distributed acoustic sensing (DAS), scholars devised a technique that can issue alerts up to 30 minutes prior to lava eruptions. This investigation demonstrates that DAS may serve as an effective instrument for examining volcanic phenomena and supplying timely warnings to the community.
The exploration was carried out in the lab of Zhongwen Zhan (PhD ’13), a professor specializing in geophysics and the Clarence R. Allen Leadership Chair and director of the Caltech Seismological Laboratory. A paper detailing the research will be published in the journal Science on April 24.
Starting from November 2023, the Reykjanes Peninsula has undergone eight lava eruptions, some of which posed significant risks to nearby communities. Although Iceland is generally known for its volcanic activity, researchers hypothesize that this specific locale may be entering a prolonged phase of heightened activity. To investigate this, Zhan and his team established a partnership with Icelandic scientists and the telecommunications company Ljósleidarinn to install DAS sensors across the peninsula for a year to enhance the understanding of volcanic activity and create an eruption early-warning system.
“The installation was remarkably swift,” states Jiaxuan Li, the lead author of the study and a former postdoctoral researcher at Caltech, now an assistant professor at the University of Houston. “We managed to establish our system using a 100-kilometer-long fiber cable within 10 days after a major magma intrusion incident on November 10, 2023. Roughly a month later, we captured our first eruption with our system. This was a significant international collaboration with tangible outcomes.”
DAS operates by directing lasers into untapped subterranean fiber-optic cables (similar to those used for internet connectivity). As vibrations travel through the cable—whether caused by an earthquake or the sounds of traffic—the laser light undergoes a phenomenon known as a phase change. Analyzing these phase changes in the laser light provides researchers insights into the waves propagating through the medium, making a 100-kilometer cable equivalent to a line of thousands of traditional seismic sensors.
Volcanic activity also induces subterranean distortions: The ground expands and contracts as magma forces its way up from shallow underground reservoirs, where it occasionally generates sufficient pressure to break through to the surface via fissures known as dikes. DAS can accurately monitor subterranean shifts on the scale of millimeters in real time, providing a much finer resolution than GPS or satellite imaging.
Throughout the year-long study, DAS gathered data on subterranean volcanic behavior, tracking how the Earth deforms in real time as magma circulates. From this information, the team developed an initial early-warning system that afforded the public between 30 minutes to several hours of notice prior to an eruption, depending on the characteristics of the magma intrusions.
Seismologist Vala Hjörleifsdóttir from Reykjavik University, a co-author of the study, had been working in Iceland on developing an eruption early-warning strategy. Notably, an active eruption site near Grindavik was endangering the lives of the town’s several thousand residents. When the Caltech researchers installed the DAS sensors, Hjörleifsdóttir worked alongside them to identify signals in the data that signaled an imminent eruption.
“One day, in August 2024, we were holding a group meeting at Caltech when my phone began to alert me with the early warning notification,” Li recalls. “Twenty-six minutes later, Vala informed us via email that the eruption had indeed occurred and that evacuation measures had been initiated.”
“This represents the most dynamic volcanic system in Iceland,” Zhan remarks. “Beyond the necessity of offering advance notifications prior to an eruption, the project holds scientific significance as we observed more magma intrusion events than we initially anticipated—those that do not reach the surface. There remains considerable work ahead, and all volcanoes exhibit unique characteristics, but DAS grants us a novel capability to observe phenomena that were previously undetectable. Our project exemplifies the efficacy of international collaboration.”
The paper is titled “Minute-scale Dynamics of Recurrent Dike Intrusions in Iceland with Fiber-Optic Geodesy.” Besides Li, Hjörleifsdóttir, and Zhan, the co-authors include Ettore Biondi, Qiushi Zhai, Shane Zhang, Xiaozhuo Wei, and Elijah Bird (MS ’24) of the Caltech Seismo Lab; Elías Rafn Heimisson (former Caltech postdoctoral scholar) and Halldór Geirsson from the University of Iceland; Simone Puel, a former Caltech postdoctoral scholar currently with Moody’s; Andy Klesh from the Jet Propulsion Laboratory, which Caltech oversees for NASA; Valey Kamalov of Valey Kamalov LLC; and Theodór Gunnarsson of Google. Financial support was provided by the Gordon and Betty Moore Foundation, the National Science Foundation (NSF), and the NSF Center for Geomechanics and Mitigation of Geohazards.