USGS Volcano Notice - DOI-USGS-NMI-2026-02-23T21:01:27+00:00

NMI/USGS Volcanic Activity Notice

Volcano: Ahyi Seamount (VNUM #284141)

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

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

Issued: Tuesday, February 24, 2026, 8:56 AM ChST
Source: U.S. Geological Survey
Notice Number: 2026/N16
Location: N 20 deg 26 min E 145 deg 1 min
Elevation: -180 ft (-55 m)
Area: Northern Mariana Islands

Volcanic Activity Summary:

No signs of volcanic unrest have been observed at Ahyi seamount since January 9, 2026, when satellite views last saw a plume of discolored water near the seamount. Distant underwater pressure sensors near Wake Island (1,410 miles east of Ahyi) have also not detected any activity from the direction of Ahyi seamount for several weeks.

Due to the apparent absence of activity, and the lack of local monitoring stations near Ahyi Seamount, the Aviation Color Code and Volcano Alert Level are being lowered to UNASSIGNED.

Recent Observations:
[Volcanic cloud height] No volcanic cloud produced
[Other volcanic cloud information] Discolored water observed above the seamount in satellite images.

Hazard Analysis:
[Other hazards] Shallow submarine eruptions may present hazards to mariners in the water above the vent.

Remarks:

Ahyi seamount is a large conical submarine volcano that rises to within 164 ft (50 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.

Contacts:

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

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

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.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20260223/2256Z)
(3) Volcano:	Ahyi Seamount (VNUM #284141)
(4) Current Color Code:	UNASSIGNED
(5) Previous Color Code:	YELLOW
(6) Source:	U.S. Geological Survey
(7) Notice Number:	2026/N16
(8) Volcano Location:	N 20 deg 26 min E 145 deg 1 min
(9) Area:	Northern Mariana Islands
(10) Summit Elevation:	-180 ft (-55 m)
(11) Volcanic Activity Summary:	No signs of volcanic unrest have been observed at Ahyi seamount since January 9, 2026, when satellite views last saw a plume of discolored water near the seamount. Distant underwater pressure sensors near Wake Island (1,410 miles east of Ahyi) have also not detected any activity from the direction of Ahyi seamount for several weeks. Due to the apparent absence of activity, and the lack of local monitoring stations near Ahyi Seamount, the Aviation Color Code and Volcano Alert Level are being lowered to UNASSIGNED.
(12) Volcanic cloud height:	No volcanic cloud produced
(13) Other volcanic cloud information:	Discolored water observed above the seamount in satellite images.
(14) Remarks:	Ahyi seamount is a large conical submarine volcano that rises to within 164 ft (50 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.
(15) Contacts:	CNMI Homeland Security and Emergency Management https://opd.gov.mp/library/agency/homeland-security-and-emergency-management.html USGS Northern Mariana Duty Scientist (907) 786-7497 http://volcano.wr.usgs.gov/cnmistatus.php Satellite information, Washington VAAC http://www.ssd.noaa.gov/VAAC/washington.html
(16) Next Notice:	A new VAN will be issued if conditions change significantly or alert levels are modified.