Monitoring hidden processes beneath Kīlauea could aid eruption forecast

The massive 2018 eruption of Kīlauea Volcano on Hawai‘i Island lasted for months, destroyed neighborhoods, and was associated with 60,000 earthquakes. A new study led by researchers at the University of Hawai‘i (UH) at Mānoa revealed Kīlauea’s magma system started behaving anomalously about a year before the eruption began. This discovery, made using a unique seismic monitoring method, suggests that tracking these hidden processes could aid eruption prediction and volcanic hazard mitigation. 

Scientists have long understood that magma moves within Kīlauea's complex plumbing system, but this study revealed a subtle, long-lasting change that may signal future events. Sin-Mei Wu, assistant professor in the Department of Earth Sciences in the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), collaborated with a team of scientists that included colleagues from the University of Miami and the University of California, San Diego to investigate Kīlauea's internal dynamics leading up to the 2018 eruptions. The team found that about a year before the 2018 eruption, the normal upward flow of magma from the mantle to the summit's shallow reservoirs was disrupted. 

“Our hypothesis is that a blockage formed between the volcano’s two summit magma reservoirs, impeding the flow, and pressure began to build beneath Kīlauea's East Rift Zone,” said Wu. 

The team also observed that the lava lake inside Halema‘uma‘u crater dropped by about 30 meters--nearly the height of a 10-story building--while pressure in the deeper magma system remained stable.

“It remains unclear whether the unusual behavior we identified was a singular event or part of a recurring pattern that could influence future eruptions,” Wu added. “However, as continuous monitoring data accumulate, we expect to gain increasingly detailed insights into Kīlauea’s inner workings and its long-term behavior.”

After analyzing the data, Wu and colleagues hypothesize that magma was being diverted sideways from the summit and into the horizontal dike system leading toward the rift zone. This atypical pattern lasted for months until a magnitude 5 earthquake on the volcano’s flank likely released the blockage, sending more pressure into the shallow summit system for the subsequent months. From that point, the Kīlauea summit remained disturbed until the start of the massive 2018 eruption.

Using ocean waves to listen to Kīlauea 

The team’s discovery was made possible by continuously monitoring Kīlauea with seismic instruments. Seismic waves are vibrations that travel through Earth, carrying information about the material they pass through. Instead of relying on energy from earthquakes, the team utilized seismic energy from a constant, natural source: ocean waves.

“The ocean provides a constant supply of seismic energy, allowing us to track the status of Kīlauea’s magma plumbing system over time, even when there are no noticeable earthquakes or ground deformation,” Wu explained. “When magma moves underground, it changes the pressure within the system and alters the surrounding rock, which we can detect with our monitoring tools.”

The study highlights the importance of the silent processes occurring beneath the surface, which can be revealed by combining seismic analysis with other geological and geophysical observations. 

“As a UH Mānoa faculty member dedicated to understanding Kīlauea, my goal is to contribute to volcanic hazard mitigation and support the safety of Hawaiʻi’s residents,” Wu added. “We hope this study, and our future work, will help unravel these fascinating processes.”