Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Friday, May 26, 2023, 6:42 AM ChST (Thursday, May 25, 2023, 20:42 UTC)

Report prepared by the U.S. Geological Survey.

20°25'12" N 145°1'48" E, Summit Elevation -259 ft (-79 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Renewed eruptive activity was detected at from Ahyi Seamount was detected in underwater pressure sensors from Wake Island (1,410 miles or 2,270 km east of Ahyi) starting on May 21, 2023, at about 10:10 PM ChST (12:10 PM UTC), and have continued through the week. Satellite images on May 22, 2023 detected a roughly 2.5 mile (4 km) plume of discolored water originating from Ahyi Seamount. Satellite images since that time have not detected additional plumes, and no activity has be observed above 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 260 feet (79 m) of the sea surface about 11 miles (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 (+/- 9 miles or 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