Hazard Notification System (HANS) for Volcanoes
NORTHERN MARIANA ISLANDS VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, January 27, 2023, 8:44 AM ChST (Thursday, January 26, 2023, 22:44 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
Evidence for a possible submarine eruption of Ahyi Seamount continued over the past week. Underwater pressure sensors near Wake Island (1,410 miles east of Ahyi), detected possible explosion signals from the direction of Ahyi on Jan. 25. No new evidence of activity was observed in satellite observations over the past week, although cloudy conditions limited observations. A plume of discolored water was observed in one high-resolution satellite image acquired on January 8. No observations indicate activity has breached the ocean surface.
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 underwater pressure sensors, 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
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CNMI Homeland Security and Emergency Management
USGS Northern Mariana Duty Scientist (907) 786-7497
Satellite information, Washington VAAC