Newest Volcano Notice Including Ahyi Seamount

NORTHERN MARIANA ISLANDS VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, December 27, 2024, 5:47 AM ChST (Thursday, December 26, 2024, 19:47 UTC)

Report prepared by the U.S. Geological Survey.

NORTHERN MARIANAS VOLCANOES
Unrest at Ahyi Seamount continues. No other eruptive activity or significant unrest was detected at the 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, all volcanoes have alert levels of UNASSIGNED. This includes Anatahan, Sarigan, Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan.

AHYI SEAMOUNT (VNUM #284141)
20°25'12" N 145°1'48" E, Summit Elevation -259 ft (-79 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Unrest at Ahyi Seamount continues. Signals from underwater activity coming from the direction of Ahyi were detected hydroacoustic array data at Wake Island on December 24 and 26 (UTC time). Satellite data from those days were obscured by clouds. A partly cloudy satellite image from December 25 showed no evidence of discolored water in the vicinity. Weak activity at Ahyi Seamount has been observed in satellite imagery off an on extending back to August 5, 2024.

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 distant hydroacoustic data closely for additional evidence for, or escalation of, volcanic activity.

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, 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.

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/

CONTACT INFORMATION:

CNMI Homeland Security and Emergency Management
http://www.cnmihsem.gov.mp/

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