A groundbreaking analysis of satellite data has revealed that the catastrophic 2018 eruption and collapse of Indonesia’s Anak Krakatau volcano which triggered a deadly tsunami was preceded by years of subtle but accelerating movements along its mountainside. Researchers at Penn State University found that the volcano’s flank had been slipping for over a decade, showing signs that could have potentially served as an early warning if monitored in real time.
The study, recently published in Geophysical Research Letters, highlights how advanced radar satellites can detect minute ground deformations, helping scientists track unstable ocean volcanoes and predict possible collapses before they occur.
“Ocean volcanoes, when unstable, can collapse catastrophically and generate tsunamis,” explained Christelle Wauthier, associate professor of geosciences at Penn State and co-author of the study. “In 2018, more than 400 people lost their lives because no one had the instruments on the ground to track these warning signs. Our study shows that, in retrospect, such collapses could be forecasted using remote sensing data.”
The research team utilized a satellite imaging technique called Interferometric Synthetic Aperture Radar (InSAR), analyzing more than a decade’s worth of data from three satellite missions—ALOS-1, COSMO-SkyMed, and Sentinel-1. Their findings revealed that the detachment fault under Anak Krakatau had experienced approximately 15 meters (50 feet) of slip between 2006 and 2018. More alarmingly, this movement showed periods of acceleration before the final collapse, suggesting that real-time monitoring of such patterns could serve as an early warning system.
“When a volcano grows through continuous eruptions, it can reach a point where the weight is too much for the underlying fault to support,” said Young Cheol Kim, the study’s lead author and a doctoral candidate at Penn State. “The process begins as a slow landslide over several years, but if it accelerates, it can indicate an imminent collapse.”
Despite the promising potential of InSAR for volcano monitoring, the study also underscored the challenges of ground-based tracking in remote or dangerous locations like Anak Krakatau. Traditional GPS-based monitoring systems require costly deployment and maintenance, and obtaining permits for placing instruments on active volcanoes can be difficult. InSAR, however, offers a viable alternative for near-real-time observations without requiring physical presence on the ground.
“If you detect a sudden acceleration of slip, it could be a critical sign of an impending collapse,” Wauthier emphasized. “For volcanoes worldwide that are susceptible to flank failure, near-real-time InSAR processing could be a game-changer in disaster preparedness.”
The findings add to a growing body of research supporting satellite-based monitoring as a crucial tool for forecasting volcanic hazards. Scientists hope that integrating such technology into global early warning systems could help prevent future tragedies similar to the 2018 Anak Krakatau disaster.
https://phys.org/news/2025-02-satellite-analysis-reveals-foreshadowed-volcanic.html