Northern Mariana Islands Volcano Observatory issues activity notice for Ahyi Seamount : Maui Now

A plume of discolored water was observed in the vicinity of Ahyi Seamount in satellite images from Monday afternoon, Jan. 1, 2024 local time, which is 20 hours ahead of Hawaiʻi.

The Northern Mariana Islands Volcano Observatory issued an activity notice saying, “It is possible that this plume is due to underwater volcanic activity however pressure sensors at Wake Island that have been used in the past to confirm underwater volcanic activity are not currently operational. More distant sensors have not registered any activity.  It is therefore not possible to confirm volcanic activity at Ahyi Seamount in independent data streams and the Aviation Color Code and Volcano Alert Level remain at UNASSIGNED.”

Observatory scientists will continue to monitor satellite data for additional evidence of discolored water associated with underwater volcanic activity.

Starting mid-October 2022, hydroacoustic sensors at Wake Island, 1,410 miles (2,270 km) east of Ahyi, began recording signals consistent with activity from an undersea volcanic source. In collaboration with the Laboratoire de Geophysique in Tahiti, a combined analysis of the hydroacoustic signals and data from seismic stations located at Guam and Chichijima Island, Japan, confirmed that the source of this activity was at or near Ahyi seamount, according to the activity notice.

Observations of discolored water above the seamount in satellite data confirmed activity at Ahyi. The activity appears to have paused beginning in early April 2023 but briefly resumed in late May 2023. 

Ahyi seamount is a large conical submarine volcano that rises to within 450 ft (137 m) of the sea surface about 11 miles (18 km) southeast of Farallon de Pajaros (Uracas) Island in the northern Marianas, about 370 miles (600 km) north of the island of Saipan. In the past, discolored water has been observed over the submarine volcano.

In 1979, the crew of a fishing boat felt shocks over the summit area and then observed upwelling of sulfur-bearing water. On April 24-25, 2001 an explosive submarine eruption was detected seismically from a seismic station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 9 miles or 15 km) at a location near the southern base of Ahyi, according to the observatory.