NORTHERN MARIANA ISLANDS WEEKLY UPDATE
U.S. Geological Survey
Friday, February 20, 2026, 8:19 AM ChST (Thursday, February 19, 2026, 22:19 UTC)
Report prepared by the U.S. Geological Survey.
AHYI SEAMOUNT (VNUM #284141)
20°26'13" N 145°1'48" E, Summit Elevation -180 ft (-55 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
No signs of significant unrest were observed in satellite data or geophysical data. The last visible plume of discolored seawater was observed on January 9.
There are no local monitoring stations near Ahyi seamount, which limits our ability to detect and characterize volcanic unrest there. We will continue to monitor satellite and distal hydroacoustic data for additional evidence for, or escalation of, volcanic activity.
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. More recently, the volcano erupted from October 2022 to May 2023 and again from December 2023 to April 2024, characterized by submarine plumes and geophysical detections of activity on the hydrophone arrays at Wake Island. The current episode of unrest began in August 2024.
NORTHERN MARIANAS VOLCANOES
No definitive signs of unrest were detected at any other Northern Mariana Island volcanoes during the past week.
Monitoring of Northern Mariana Islands Volcanoes
Northern Mariana Island volcanoes are monitored using seismo-acoustic sensors on Saipan, and by examining satellite imagery. We also use distant seismic stations in Guam and Chichijima, Japan, and hydroacoustic data from Wake Island, when available.
This level of monitoring can detect significant volcanic activity in the CNMI but cannot provide advanced warning of eruptions.
Due to a lack of geophysical monitoring on any of the volcanic islands, the following volcanoes have alert levels of UNASSIGNED: Anatahan, Sarigan, Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan.
For definitions of Aviation Color Codes and Volcano Alert Levels: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes
SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/
CONTACT INFORMATION: 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