On 26 April both the Aviation Color Code and the Volcano Alert Level for Ahyi Seamount were lowered to Unassigned because signs of unrest had decreased, and no indication of submarine volcanic activity had occurred for at least four weeks. Observations of discolored water near the seamount were last identified in satellite images in late March 2023, and underwater activity based on acoustic signals had been negligible since early April 2023.

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