SAIPAN — The Commonwealth Office of Homeland Security and Emergency Management (HSEM) is maintaining heightened watch over Ahyi Seamount after partner agencies noted renewed signs of submarine unrest. The volcano’s status remains at Advisory with an Aviation Color Code of Yellow, indicating activity above background that does not currently pose a hazard to aviation.
HSEM said it is coordinating closely with the Alaska Volcano Observatory and U.S. Geological Survey, along with the National Weather Service Guam, the Pacific Tsunami Warning Center and the U.S. Coast Guard. Analysts have reported plumes of discolored water above Ahyi’s summit area in recent days, a typical surface clue that hot, mineral-rich fluids are rising from the seafloor. No volcanic cloud has been observed and there are no reports of ash.
Ahyi is a large conical submarine volcano that rises to within about 246 feet of the ocean surface. It sits roughly 11 miles southeast of Farallon de Pajaros (Uracas) and is composed primarily of andesite and basalt, rocks common to volcanoes north of Saipan.
While Ahyi rarely makes headlines, it has a track record that keeps scientists and mariners cautious. According to USGS, the crew of a fishing boat felt a series of shocks over the summit, followed by upwelling of sulfur-bearing water back in 1979. On April 24–25, 2001, instruments as far away as Rangiroa Atoll in the Tuamotu Archipelago detected an explosive event that was later located near Ahyi’s southern base. An eruption in April–May 2014 was confirmed by NOAA divers and by hydroacoustic and seismic sensors. The most recent eruptive period was recorded in 2023.
For now, officials emphasize that the current signs point to unrest rather than an ongoing eruption. Still, shallow submarine activity can be hazardous directly above the vent, where unexpected blasts, discolored water, floating pumice or gas-rich upwelling can reduce visibility and damage hulls or engines. Mariners are urged to steer clear of the immediate summit area and to heed any maritime advisories.
HSEM will continue to share updates from USGS and partner agencies as new data arrive. Residents are encouraged to follow official channels for verified information and to avoid circulating unconfirmed rumors about the activity.
