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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 15.62°N
  • 145.57°E

  • -230 m
    -754 ft

  • 284202
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Ruby.

The Global Volcanism Program has no Weekly Reports available for Ruby.

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

10/1995 (BGVN 20:10) Submarine eruption

Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC + 10 hours)

10/1995 (BGVN 20:10) Submarine eruption

Ruby is a prominent, active submarine volcano in the Mariana Arc (2,300 km S of Tokyo) located NW of the Island of Saipan (figure 1). Although signs of an eruption were first noted by fishermen about 11 October, initial attempts to confirm their early observations failed. On 23 October fishermen reported that they could hear submarine explosions in that vicinity. A vessel from the Wildlife and Emergency Management Office of the Commonwealth of the Northern Mariana Islands confirmed these reports. An Associated Press news report stated that early on 25 October observers had seen dead fish and bubbles, and had smelled a sulfurous odor. On 27 October the Pacific Daily News reported the eruption site as 15°36'22"N, 145°34'33"E (15.6061°N, 145.5758°E). This spot clearly lies on the edifice identified by Bloomer and others (1985, p. 215) as Ruby (only ~1.7 km from the point specified in this report's heading).

Figure 1. Index map and bathymetric map (depths in meters) showing seamounts near Saipan Island, including the known active centers Esmeralda Bank and Ruby (after Bloomer and others, 1989).

Prior to the eruption, published estimates of the summit elevation suggested a 230-m depth, a refinement an earlier estimate of 549 m (Bloomer and others, 1985, p. 215). On 6 October 1995, the Pacific Daily News report stated the summit was measured at 185-m depth. This newly reported depth remains unconfirmed. According to Mike Blackford, on 23 October a marine depth finder reportedly measured a depth of ~60 m. Although this could be a reflection off the eruptive plume, in the absence of any discussion of instrument type and calibration, this depth remains equivocal.

According to Koyanagi and others (1993), the two seismic stations nearest the eruption were on Saipan (~50 km SE of Ruby) and Pagan islands (~130 km N of Saipan), both too distant to detect subtle seismic effects. Despite the lack of a nearby seismic station, tremor appeared on seismic records at the time of the eruption and the next day. Given the temporal coincidence between the eruption and the tremor, the two were probably associated.

A fish recovered at the eruption site was found to have small particles of ash in its gills and HVO researchers planned to analyze this ash. News of the eruption caused concern about a possible local tsunami and on 25 October, the Commonwealth of the Northern Mariana Islands issued an alert.

Evidence for Ruby's active status came from 1966 hydrophone data, followed later by dredging of extremely fresh volcanic rocks bearing plagioclase, clinopyroxene, and olivine (Bloomer and others, 1985).

References. Bloomer, S.H., Stern, R.J., and Smoot, N.C., 1989, Physical volcanology of the submarine Mariana and Volcano arcs: Bull. Volcanol., no. 51, p. 210-234.

Koyanagi, R., Kojima, G., Chong, F., and Chong, R., 1993, Seismic monitoring of earthquakes and volcanoes in the Northern Mariana Islands: 1993 summary report: Prepared for the Office of the Governor, Commonwealth of the Northern Mariana Islands, Capitol Hill, Saipan MP 96950 (revised 21 February 1993), 34 p.

Information Contacts: Robert J. Stern, Center for Lithospheric Studies, University of Texas at Dallas, Box 830688, Dallas, TX 75083-0688 USA (Email:; Robert Koyanagi, USGS Hawaiian Volcano Observatory, Hawaii Volcanoes National Park, HI 96718, USA; Ramon C. Chong, Commonwealth of the Northern Mariana Islands (CNMI), Disaster Control Office, Capitol Hill, Saipan, MP 96950 USA; Mike Blackford, Pacific Tsunami Warning Center, 91-270 Fort Weaver Road, Ewa Beach HI 96706, USA; Associated Press; Pacific Daily News.

Ruby, a basaltic submarine volcano that rises to within 230 m of the sea surface near the southern end of the Mariana arc NW of Saipan, was detected in eruption in 1966 by sonar signals (Norris and Johnson, 1969). In 1995 submarine explosions were heard, accompanied by a fish kill, sulfurous odors, bubbling water, and the detection of volcanic tremor.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1995 Oct 11 (?) 1995 Oct 25 Confirmed 0 Historical Observations
1966 Apr 21 ± 7 days 1966 May Confirmed 0 Hydrophonic

The Global Volcanism Program has no synonyms or subfeatures listed for Ruby.

Ruby submarine volcano in the southern Mariana arc is seen in this bathymetric view looking from the NW with two times vertical exaggeration. Depths in this image range from 184 to 2955 meters. Ruby, a submarine volcano that rises to within 230 m of the sea surface NW of Saipan, was detected in eruption in 1966 by sonar signals. In 1995 submarine explosions were heard, accompanied by a fish kill, sulfurous odors, water bubbling, and the detection of volcanic tremor.

Image courtesy of Susan Merle (Oregon State University/NOAA Vents Program).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Bloomer S H, Stern R J, Smoot N C, 1989. Physical volcanology of the submarine Mariana and Volcano arcs. Bull Volc, 51: 210-224.

Johnson R H, 1973. Acoustic observations of nonexplosive submarine volcanism. J Geophys Res, 78: 6093-6096.

Kohut E, 2007. . (pers. comm.).

Norris R A, Johnson R H, 1969. Submarine volcanic eruptions recently located in the Pacific by SOFAR hydrophones. J Geophys Res, 74: 650-664.

Volcano Types


Tectonic Setting

Subduction zone
Crustal thickness unknown

Rock Types

Basalt / Picro-Basalt


Within 5 km
Within 10 km
Within 30 km
Within 100 km

Affiliated Databases

Large Eruptions of Ruby Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.