USGS Volcano Notice - DOI-USGS-NMI-2023-05-21T11:49:26-07:00

NMI/USGS Volcanic Activity Notice

Volcano: Ahyi Seamount (VNUM #284141)

Current Volcano Alert Level: ADVISORY
Previous Volcano Alert Level: UNASSIGNED

Current Aviation Color Code: YELLOW
Previous Aviation Color Code: UNASSIGNED

Issued: Tuesday, May 23, 2023, 6:39 AM ChST
Source: U.S. Geological Survey
Notice Number: 2023/N124
Location: N 20 deg 25 min E 145 deg 1 min
Elevation: -449 ft (-137 m)
Area: Northern Mariana Islands

Volcanic Activity Summary:

Signals consistent with eruptive activity at Ahyi seamount began to be observed in underwater pressure sensors at Wake Island beginning on May 21, 2023, at about 10:10 PM ChST (12:10 PM UTC) and are continuing. A plume of discolored sea water was observed above the area of the previously active vent in a satellite image on May 22, 2023, at 10:43 AM ChST (00:43 UTC). Due to this renewed activity at Ahyi Seamount The Aviation Color Code and Volcano Alert Level are being raised to YELLOW/ADVISORY.

Starting mid-October 2022, hydroacoustic sensors at Wake Island, 1,410 miles (2,270 km) east of Ahyi, began recording signals consistent with activity from an undersea volcanic source. In collaboration with the Laboratoire de Geophysique in Tahiti, a combined analysis of the hydroacoustic signals and data from seismic stations located at Guam and Chichijima Island, Japan, confirmed that the source of this activity was at or near Ahyi seamount. Observations of discolored water above the seamount in satellite data confirmed activity at Ahyi. The activity appears to have paused beginning in early April but has now resumed.

Recent Observations:
[Volcanic cloud height] No volcanic cloud produced
[Other volcanic cloud information] Unknown

Hazard Analysis:
[Other hazards] Shallow submarine eruptions may present hazards to mariners in the water above the vent.

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.

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

Next Notice:

A new VAN will be issued if conditions change significantly or alert levels are modified.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20230522/2039Z)
(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:	2023/N124
(8) Volcano Location:	N 20 deg 25 min E 145 deg 1 min
(9) Area:	Northern Mariana Islands
(10) Summit Elevation:	-449 ft (-137 m)
(11) Volcanic Activity Summary:	Signals consistent with eruptive activity at Ahyi seamount began to be observed in underwater pressure sensors at Wake Island beginning on May 21, 2023, at about 10:10 PM ChST (12:10 PM UTC) and are continuing. A plume of discolored sea water was observed above the area of the previously active vent in a satellite image on May 22, 2023, at 10:43 AM ChST (00:43 UTC). Due to this renewed activity at Ahyi Seamount The Aviation Color Code and Volcano Alert Level are being raised to YELLOW/ADVISORY. Starting mid-October 2022, hydroacoustic sensors at Wake Island, 1,410 miles (2,270 km) east of Ahyi, began recording signals consistent with activity from an undersea volcanic source. In collaboration with the Laboratoire de Geophysique in Tahiti, a combined analysis of the hydroacoustic signals and data from seismic stations located at Guam and Chichijima Island, Japan, confirmed that the source of this activity was at or near Ahyi seamount. Observations of discolored water above the seamount in satellite data confirmed activity at Ahyi. The activity appears to have paused beginning in early April but has now resumed.
(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.