Report on Ahyi (United States) — 23 November-29 November 2022
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
23 November-29 November 2022
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2022. Report on Ahyi (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 November-29 November 2022. Smithsonian Institution and US Geological Survey.
20.42°N, 145.03°E; summit elev. -75 m
All times are local (unless otherwise noted)
Signs of unrest at Ahyi Seamount have been observed in satellite and remote geophysical data, starting in mid-October. Hydroacoustic signals continued to be observed but had declined in the previous few weeks. Discolored water over the seamount was first visible on 18 November and persisted, possibly from either degassing or an eruption. On 29 November the Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level was raised to Advisory (the second lowest level on a four-level scale).
Geological Summary. Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.
Source: US Geological Survey