USGS Volcano Notice - DOI-USGS-NMI-2023-09-19T16:42:00-08:00

A submarine eruption at Ruby seamount on September 14–15 was detected in satellite imagery and seismoacoustic signals. In response to this activity at Ruby, the Aviation Color Code and Volcano Alert Level were raised from UNASSIGNED to YELLOW/ADVISORY on September 19. 

Since this eruption, no evidence of further activity has been detected in regional seismic and infrasound data. The plume of discolored water from the eruption has drifted slowly east and today was visible in satellite imagery in the ocean between Saipan and Anatahan. No further activity at Ruby has been observed in satellite imagery. No volcanic gas emissions have been detected in satellite data associated with the eruption or in the days after. Haze reported from Guam to Saipan is most likely from the recent eruption of Kīlauea volcano in Hawaiʻi and not the submarine activity at Ruby.

It is possible that further eruptive activity could occur at Ruby. There are no local monitoring stations at Ruby, which limits our ability to detect and characterize volcanic unrest there. The volcano is monitored by a regional geophysical monitoring network, including a station at Saipan (50 km away) as well as others in Guam, Japan, and an underwater pressure sensor at Wake Island.

Ruby is a submarine volcano that rises to within 230 m of the sea surface near the southern end of the Mariana arc northwest of the island of Saipan. The volcano was first detected in eruption in 1966 by sonar signals. In 1995, submarine explosions were heard, accompanied by a fish kill, sulfurous odors, bubbling water, and the detection of volcanic tremor.