An eruption at submarine Ruby volcano, near the southern end of the Mariana arc, was detected on Thursday, September 14, 2023. This was based on seismoacoustic signals from a monitoring station in Saipan and satellite imagery that captured a submarine plume. The last known eruption at this volcano took place in 1995.

A submarine plume was detected in satellite imagery at approximately 20:50 UTC on September 14.

Before the detection of this plume, geophysical data had not captured the onset of the eruption. However, a closer look at seismoacoustic data from a geophysical monitoring station situated 50 km (31 miles) southeast of the volcano, in Saipan, revealed eruption signals that began at 04:27 UTC on September 15. This volcanic activity was also identified by other regional geophysical monitoring systems throughout the Pacific.

By September 16, satellite images showed that the plume had dispersed, and subsequent monitoring from geophysical networks didn’t detect any further volcanic activity. Due to the eruption at Ruby, officials have now elevated the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY.

Given the recent activity, experts believe that there’s a possibility of future eruptions at Ruby. Monitoring of the volcano is done by a comprehensive regional geophysical network, which includes stations in locations such as Saipan as well as in Guam, Japan, and even an underwater pressure sensor located at Wake Island. The analysis of this geophysical data was conducted in association with the Laboratoire de Geophysique situated in Tahiti.

The plume was again detected in satellite imagery acquired by the Sentinel-2 satellite on September 19.