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USGS Volcano Notice - DOI-USGS-NMI-2024-03-28T22:05:57+00:00


U.S. Geological Survey
Friday, March 29, 2024, 8:25 AM ChST (Thursday, March 28, 2024, 22:25 UTC)

Report prepared by the U.S. Geological Survey.

20°25'12" N 145°1'48" E, Summit Elevation -259 ft (-79 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Small (less than 2 km long) plumes of discolored ocean water were observed near Ahyi Seamount in satellite images on March 22, 24, 25, and 27. Underwater pressure sensors near Wake Island (1,410 miles east of Ahyi) detected signals from the direction of Ahyi on March 22, 24, 25, and 26. These observations suggest that weak submarine volcanic activity continues at the seamount. The last plume observed before March 22 was on March 5. 

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 available remote underwater pressure sensors, seismic, and satellite data closely.

Ahyi seamount is a large conical submarine volcano that rises to within 260 feet (79 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, an eruption from October 2022 to May 2023 occurred, characterized by submarine plumes and geophysical detections of activity on the hydrophone arrays at Wake Island.

No eruptive activity or significant unrest was detected at other Northern Mariana Islands volcanoes during the past week. 

Monitoring the volcanoes of the Northern Mariana Islands

Volcanoes of the Northern Mariana Islands are monitored using seismo-acoustic sensors on Saipan, distant seismic stations in Guam and Chichijima, Japan, hydroacoustic data from Wake Island, and by examining satellite imagery.

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, Anatahan and Sarigan volcano alert levels are designated UNASSIGNED. Other volcanoes in the CNMI including Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan are not seismically monitored and are also normally designated UNASSIGNED.

For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://volcanoes.usgs.gov/activity/alertsystem/index.php

SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/


CNMI Homeland Security and Emergency Management

USGS Northern Mariana Duty Scientist (907) 786-7497

Satellite information, Washington VAAC