Researchers discovered a unique seismic signal before the eruption of the Hongatonga-Hungahapai volcano in January 2022, which may provide an early warning for marine volcanic eruptions. By analyzing Rayleigh waves detected 750 kilometers away, scientists believe that fractures in the earth's crust caused seawater to mix with magma, triggering volcanic eruptions.

Image of the Hunga volcano eruption from the National Oceanic and Atmospheric Administration's GOES-17 satellite. Image source: National Oceanic and Atmospheric Administration

Earthquake waves issue early warning

Just 15 minutes before the massive Hunga Tonga-Hungahapai volcano erupted in January 2022, two remote monitoring stations recorded seismic waves. Researchers now believe these early signals could help predict similar eruptions at other remote ocean volcanoes.

According to the researchers, the seismic waves were likely caused by ruptures in weak areas of the oceanic crust beneath the crater walls. This break allows seawater and magma to mix in the space above the volcano's underground magma chamber, triggering a strong explosive reaction that triggers a volcanic eruption.

The study, published in Geophysical Research Letters, provides new insights into early warning signs of volcanic eruptions. The journal is a public publication of the American Geophysical Union and publishes high-impact reports closely related to Earth and space science.


On January 15, 2022, the GOES-17 satellite captured images of umbrella clouds produced by the underwater eruption of the Hunga Tonga-Hunga Hapai volcano. Additionally, a crescent-shaped bow blast and numerous lighting blasts can be seen. Source: NASA Earth Observatory photo by Joshua Stevens using GOES imagery provided by NOAA and NESDIS.

Disaster reduction potential

The findings build on previous work by researchers monitoring remote volcanoes. In this case, Rayleigh waves (a type of seismic wave that moves across the Earth's surface) were detected 750 kilometers (about 466 miles) from the volcano.

Mie Ichihara, a volcanologist at the University of Tokyo and a co-author of the study, said: "Early warnings are very important for disaster reduction. Island volcanoes can trigger tsunamis, which is a major danger."

A silent precursor to a violent eruption

Hunga Tonga-Hunga Ha'apai is a marine volcano in the western Pacific Ocean of the Kingdom of Tonga. The seamount is formed when the Pacific Plate subducts beneath the Australian Plate, a process that generates magma and causes volcanic eruptions.

On January 15, 2022, the volcano erupted with record-breaking energy, injecting 58,000 Olympic swimming pools of water vapor into the stratosphere, triggering an unprecedented lightning storm and triggering a tsunami. The massive eruption was preceded by a smaller eruption on January 14, and preceded by a month of eruptive activity.

Researchers are still debating the exact time the eruption began, though most agree it began shortly after 4:00 UTC. New research reports that Rayleigh waves begin around 3:45 UTC.

Rayleigh wave detection

Researchers used seismic data to analyze Rayleigh waves, which were detected by instruments at seismic stations on the islands of Fiji and Futuna but were not felt by humans. While Rayleigh waves are a common feature of volcanic eruptions and earthquakes, researchers believe the waves mark a precursor event and may be the cause of large-scale volcanic eruptions.

"Many volcanic eruptions are preceded by seismic activity," said Takuro Horiuchi, lead author of the study and a graduate student in volcanology at the University of Tokyo. "However, this seismic signal is weak and can only be detected within a few kilometers around the volcano. In contrast, this seismic signal traveled a long distance, indicating that this was a huge seismic event. We believe that abnormally large movements began as precursors."

The secret of seamounts

Scientists may never know exactly what caused this massive "crater-forming" eruption, but Ichihara believes the process didn't happen instantly. Instead, she believes this precursor event was the beginning of underground processes that ultimately lead to volcanic eruptions.

But determining the origin of these rare, giant eruptions is difficult. "Very few crater-forming eruptions have been observed, and even fewer crater-forming eruptions have been witnessed in the ocean," Ichihara said. "This gives one hypothesis for the process leading to the crater formation, but I wouldn't say it's the only hypothesis."

Regardless, detecting an early eruption signal could give island nations and coastal areas more valuable time to prepare in the face of an impending tsunami - even if the signal cannot be felt at the surface.

"We did not expect to use this analysis method in real time during a volcanic eruption. But maybe the next time a major underwater eruption occurs, local observatories can identify it in the data."

Compiled from /ScitechDaily