On 5 December the US Geological Survey reported that signs of unrest at Ahyi Seamount were observed during the previous week. Single detections from Ahyi's direction were detected at underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi) on 29 and 30 November. Slightly discolored water was seen a few hundred meters E of the seamount in high-resolution satellite images on 30 November. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale).

Geological Summary. Ahyi seamount is a large conical submarine volcano ~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