USGS Volcano Notice for Aviation - DOI-USGS-NMI-2023-09-18T19:07:17-07:00

Analysis of seismoacoustic signals and observations of a submarine plume in satellite imagery are consistent with an eruption at Ruby seamount beginning the morning of September 15 ChST. Satellite imagery shows a submarine plume of discolored water by sunrise at ~20:50 UTC on September 14 (06:50 ChST September 15). This plume does not breach the ocean surface. Onset of the eruption prior to the plume detection is not observed in geophysical data. Retrospective analysis of seismoacoustic data from a geophysical monitoring station on Saipan, 50 km to the southeast of the volcano, capture eruption signals beginning at 14:27 ChST on September 15 (04:27 UTC). The activity was also picked up on other regional geophysical monitoring networks in the Pacific. The plume is detached in satellite imagery by the morning of September 16 and no activity has since been observed on geophysical networks. Due to this activity at Ruby, the Aviation Color Code and Volcano Alert Level are being raised to YELLOW/ADVISORY.

It is possible that further eruptive activity could occur at Ruby. 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. Analysis of the geophsyical data was done in collaboration with the Laboratoire de Geophysique in Tahiti.

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.