Newest Volcano Notice Including Ahyi Seamount

NMI/USGS Volcanic Activity Notice

Volcano: Ahyi Seamount (VNUM #284141)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: UNASSIGNED

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: UNASSIGNED


Issued: Thursday, July 16, 2026, 10:13 AM ChST
Source: U.S. Geological Survey
Notice Number: 2026/N41
Location: N 20 deg 26 min E 145 deg 1 min
Elevation: -180 ft (-55 m)
Area: Northern Mariana Islands

Summary: Submarine plumes seen in satellite data reflecting volcanic unrest or undersea eruption. Change of Aviation Color Code to YELLOW and Volcano Alert Level to Advisory.

Volcanic Activity:

Signs of unrest at Ahyi Seamount have been observed in recent satellite images over the past few weeks. Small plumes of discolored water were observed drifting less than 0.3 miles (0.5 km) away from the volcano in satellite images on July 1, 7, and 11. Small plumes have been observed intermittently in clear satellite images over the last few months, but recent images show more discrete plume shapes suggesting more vigorous activity. No significant activity has been detected from the direction of Ahyi Seamount in hydroacoustic array data at Wake Island. 

The plumes are likely the result of gas release into the water column, these could reflect vigorous hydrothermal degassing or be associated with an ongoing effusive eruption. In either case, the observations indicate increased volcanic unrest and potential for activity to breach the ocean surface.

Eruptive activity at Ahyi Seamount may present a hazard to mariners in the water above and near the volcano. The summit has shallowed over the course of previous eruptions to 180 feet (55 m) below sea level, but the lack of local real-time data means we are unable to forecast or warn of impending eruptions. The Aviation Color Code and Volcano Alert Level are being raised to YELLOW and ADVISORY. We will continue to monitor satellite and distal hydroacoustic data for additional evidence for, or escalation of, volcanic activity.

Remarks:

Ahyi seamount is a large conical submarine volcano that rises to within 180 feet (55 m) of the sea surface about 11 miles (18 km) southeast of the island of Farallon de Pajaros (Uracas) in the Northern Mariana Islands. Water discoloration has been observed over the submarine volcano during previous periods of activity, and in 1979 the crew of a fishing boat felt shocks over the summit area followed by upwelling of sulfur-bearing water. From April 24 to 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; the summit of the seamount lies within the location uncertainty. Another eruption was detected from April 24 to May 17, 2014, using data from seismometers located on subaerial volcanoes in the Northern Mariana Islands and hydrophone arrays at Wake Island. NOAA divers also reported hearing explosions while conducting coral reef research on nearby Farallon de Pajaros. The 2014 eruption of Ahyi formed a new crater near the summit of the volcano and a large landslide chute developed on its southeast flank. The most recent eruptive activity began in 2022. 

Contacts:

USGS Northern Mariana Duty Scientist (907) 786-7497
http://volcano.wr.usgs.gov/cnmistatus.php

CNMI Homeland Security and Emergency Management
https://opd.gov.mp/library/agency/homeland-security-and-emergency-management.html

Satellite information, Washington VAAC
http://www.ssd.noaa.gov/VAAC/washington.html

Next Notice:

A new VAN will be issued if conditions change significantly or alert levels are modified.