USGS Volcano Notice for Aviation - DOI-USGS-NMI-2024-01-13T14:48:10-08:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20240113/2250Z)
(3) Volcano:	Ahyi Seamount (VNUM #284141)
(4) Current Color Code:	YELLOW
(5) Previous Color Code:	UNASSIGNED
(6) Source:	U.S. Geological Survey
(7) Notice Number:	2024/N5
(8) Volcano Location:	N 20 deg 25 min E 145 deg 1 min
(9) Area:	Northern Mariana Islands
(10) Summit Elevation:	-259 ft (-79 m)
(11) Volcanic Activity Summary:	Signs of unrest at Ahyi Seamount have been observed in satellite data over the past few weeks. Plumes of discolored water were observed drifting 1.5–6.2 miles (2.4–10 km) away from the volcano in satellite images on December 24 and 31, 2023 and January 4 and 10, 2024. Nothing significant has been detected from the direction of Ahyi in hydroacoustic array data at Wake Island; however, submarine plumes have been observed at Ahyi in the past without clear hydroacoustic signals. Due to the increased likelihood of an underwater eruption occurring at Ahyi Seamount, the Aviation Color Code and Volcano Alert Level are being raised to YELLOW and ADVISORY. We will continue to monitor satellite and distal hydroacoustic data for additional evidence of volcanic activity. An undersea eruption at Ahyi Seamount was last detected starting mid-October 2022. The activity appeared to pause beginning in early April 2023 but briefly resumed in late May 2023.
(12) Volcanic cloud height:	No volcanic cloud produced
(13) Other volcanic cloud information:	Unknown
(14) Remarks:	Ahyi seamount is a large conical submarine volcano that rises to within 450 ft (137 m) of the sea surface about 11 miles (18 km) southeast of Farallon de Pajaros (Uracas) Island in the northern Marianas, about 370 miles (600 km) north of the island of Saipan. In the past, discolored water has been observed over the submarine volcano. In 1979, the crew of a fishing boat felt shocks over the summit area and then observed upwelling of sulfur-bearing water. On April 24-25, 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.
(15) Contacts:	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
(16) Next Notice:	A new VAN will be issued if conditions change significantly or alert levels are modified.