Signs of unrest at Ahyi Seamount were observed during the previous few weeks. Plumes of discolored water drifting as far as 10 km from the vent were identified in satellite data on 24 December 2023 and again on 4 and 10 January 2024. Hydroacoustic arrays located on Wake Island did not record any significant signals, though submarine plumes have been observed in the past without clear hydroacoustic evidence. The Aviation Color Code was raised to Yellow (the second level on a four-color scale) and the Volcano Alert Level was raised to Advisory (the second level on a four-level scale) on 14 January because the likelihood of an eruption had increased. No unusual activity observed in satellite data during 15-17 January.

Geological Summary. Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the ocean surface ~18 km SE of the island of Farallon de Pajaros in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.

Source: US Geological Survey