Underwater eruption at Ahyi Seamount, Northern Mariana Islands
An underwater volcanic eruption is occurring at Ahyi Seamount, located about 18 km (11 miles) southeast of Farallon de Pajaros (Uracas) in the Northern Mariana Islands, part of the Mariana Volcanic Arc in the western Pacific Ocean.
Submarine eruption at Ahyi Seamount on November 27, 2022. Image credit: USGS/Landsat-8
- Satellite observations since early August 2024 have detected discolored water plumes and the potential presence of floating pumice.
- These signs led authorities to raise the Volcano Alert Level and Aviation Color Code on November 21, indicating increased volcanic activity beneath the ocean’s surface.
An underwater volcanic eruption is taking place at Ahyi Seamount, accompanied by plumes of discolored water and the possibility of floating pumice.
In response, the Northern Mariana Islands Volcano Observatory upgraded the Volcano Alert Level to ADVISORY and the Aviation Color Code to Yellow on November 21.
Ahyi Seamount is a massive, conical submarine volcano in the Northern Mariana Islands, approximately 18 km (11 miles) southeast of Farallon de Pajaros (Uracas).
The crest of the seamount is roughly 75 m (246 feet) below sea level. This isolated underwater volcano is a component of the Mariana Volcanic Arc in the western Pacific Ocean.
Ahyi Seamount is situated in a tectonically active subduction zone, where the Pacific Plate is being driven beneath the Philippine Sea Plate.
The current volcanic activity has been going on since early August 2024, with more satellite observations in recent weeks.
While hydroacoustic sensors, which detect underwater sound waves, have not yet captured significant signals, past eruptions demonstrate that undersea plumes can form without strong acoustic data.
Monitoring relies heavily on satellite imagery and remote hydrophones due to the absence of local seismic stations.
Previous eruptions have shown that undersea plumes can form without substantial hydroacoustic signals. Due to the lack of local seismic stations, continuous monitoring via satellites and remote hydrophones is required.
This geological setting of Ahyi Seamount is prone to frequent volcanic activity. Past eruptions include a notable event in 1979, when a fishing boat crew felt shocks near the summit, followed by upwelling of sulfur-bearing water.
In April 2001, an explosive eruption was detected seismically from a station on Rangiroa Atoll in the Tuamotu Archipelago.
Another significant eruption from April to May 2014 was identified through NOAA divers, hydroacoustic sensors, and seismic stations, forming a new summit crater and a landslide chute on the southeast flank.
More recently, Ahyi erupted between October 2022 and May 2023 and again from December 2023 to April 2024.
Because the seamount is located distant from inhabited regions, there has been no recorded direct influence on residents.
Mariners are advised to exercise caution in the region due to potential hazards from floating pumice and volcanic debris.
References:
1 NORTHERN MARIANA ISLANDS VOLCANO OBSERVATORY WEEKLY UPDATE – USGS – November 22, 2024
2 Ahyi geological summary – GVP – Accessed November 23, 2024
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