Hydroacoustic Evidence for Offshore Lava Emplacement During the 2018 Kīlauea Eruption

• Published in: Geophysical research letters 2024-10, Vol.51 (20), p.n/a
• Main Authors: Atkins, C., Costa, O., Caplan‐Auerbach, J.
• Format: Article
• Language: English
• Subjects: Boating; Broadband; Coasts; Eruptions; Explosives detection; hydrophone; Hydrophones; hydrovolcanic; Kilauea; Lava; Lava flows; lava‐water interaction; Microphones; Ocean floor; Offshore; Recreation; Seawater; Shallow water; Transmission loss; Underwater acoustics; Volcanic deposits; Volcanic eruptions; Volcanoes
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL110885

During the 2018 Kīlauea eruption, over half the erupted lava was deposited on the seafloor. Lava flows crossing the shoreline generated sounds that were recorded by a network of hydrophones. We show that short‐duration, broadband signals associated with lava‐water interactions occurred throughout the eruption but increased in number when the Ahalanui ocean entry initiated on July 11. These terminated in early August coincident with the eruption's end. We compare hydroacoustic data with transmission loss models and eruption photographs to show that coastal explosive activity was poorly recorded by the hydrophone network. Similarly, strong hydroacoustic signals did not correlate with observed activity. These results suggest that acoustic signals were generated by lava flowing up to 100 s of meters offshore. Offshore lava flows can be hazardous to boaters, but hydrophones provide a means by which these hazards can be detected. Plain Language Summary During the 2018 eruption of Kīlauea volcano, Hawai'i, lava flowed past the coastline and into the sea where it was deposited on the volcano's submarine flank. In this study we show that the interaction of lava and sea water created noise that was detected by a network of hydrophones (underwater microphones) placed offshore. Lava‐water interactions that occurred very close to the coastline, however, were not well‐recorded by the hydrophones, suggesting that sound was trapped in the shallow water. Other strong sounds were recorded when no obvious activity was visible at the coast. These observations suggest lava was flowing much farther offshore than was observed from the surface, potentially posing a threat to boaters and coastal observers. Key Points Lava flows entering the ocean during the 2018 Kīlauea eruption generated sounds that were detected by hydrophones Explosive activity observed near the coastline was only weakly detected by the hydrophones Signals detected by the hydrophones may have initiated >100 m from the coast, suggesting that lava advanced well offshore