Approximately 15 minutes before the underwater volcano Hunga Tonga-Hunga Ha'apai erupted in 2022, a seismic wave was detected by monitoring stations located 750 km away.On January 15, 2022, the Hunga Tonga-Hunga Ha'apai volcano in the Tonga archipelago unleashed a powerful eruption, the most intense ever recorded with modern equipment, shaking the South Pacific. A recent study published in Geophysical Research Letters identifies a mysterious signal that occurred just before this catastrophic event.