NORTHERN MARIANA ISLANDS VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, December 2, 2022, 9:44 AM ChST (Thursday, December 1, 2022, 23:44 UTC)
Report prepared by the U.S. Geological Survey.
AHYI SEAMOUNT VOLCANO (VNUM #284141)
20°25'12" N 145°1'48" E, Summit Elevation -449 ft (-137 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Unrest continues at Ahyi Seamount. The aviation color code and alert level were raised to Yellow and Advisory on November 29, 2022, following the detection of signals on the hydroacoustic array at Wake Island (1,410 miles east of Ahyi) beginning in mid-October and observations of discolored water above the seamount in satellite images beginning in early November. Clouds obscured the region above the seamount in satellite images for most of the week but plumes of discolored water were observed above the volcano when images were clear on November 26 and December 1. The hydroacoustic detections that began in mid-October continue but have been declining with typically a few detections per day observed over the past week.
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 available remote hydrophonic, seismic, and satellite data closely.
Ahyi seamount is a large conical submarine volcano that rises to within 79 m of the sea surface about 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 (+/- 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.
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/
CNMI Homeland Security and Emergency Management
USGS Northern Mariana Duty Scientist (907) 786-7497
Satellite information, Washington VAAC