| Ruby Seamount | |
| Depth: | 175m (574feet) |
| Location: | Pacific Ocean |
| Group: | Izu–Bonin–Mariana Arc |
| Coordinates: | 15.62°N 145.57°W |
| Country: | Commonwealth of Northern Mariana Islands, United States |
| Type: | Seamount |
| Last Eruption: | 15 September 2023 |
| Map: | File:Ruby bathymetry map 600.jpg |
Ruby Seamount is an active volcanic seamount in the Northern Mariana Islands region of the Pacific Ocean about 50km (30miles) north-west of Saipan.[1] [2] It is in a region where the Pacific Plate is subducting under the Philippine Sea Plate producing arc volcanism.
A submarine eruption occurred during a period of about 12 hours between 14 and 15 September 2023, and it also erupted in 1966 and between 11 and 23 October 1995.[1] [2]
Ruby Seamount is a stratovolcano with a more shallow southern peak,[1] and is part of the nine volcano Southern Seamount Province of the Mariana Arc, in the Izu–Bonin–Mariana Arc.[3] Its location is consistent with it being a back-arc extension associated volcano. Samples of lava have been characterised as arc tholeiitic basalts,[3] suggestive that the magma source was from mantle overlying, not beneath, the subducting Pacific Plate.[4] The age of the volcano is unknown but nearby basalts have been dated at about 2 million years old,[4] so it likely started forming more recently than this.
Hydrothermal activity was demonstrated in 2006 with alkaline, ferrous ion and carbon dioxide venting at 200m (700feet) depth.[5] The ratio of CO2 / 3He flux observed at Ruby is amongst the highest ever reported, which is consistent with volcanism involving a deep magma source from slab derived carbonate containing rocks.[5]
Prior to the 1995 eruption the depth was accepted as 230m (760feet),[2] but several reports of shallower depths followed the eruption including one of only about 60m (200feet) exist.[1] A high quality survey in 2003 gave a depth of 180m (590feet) with the peak of North Ruby having a depth of 726m (2,382feet).[6] The next high quality survey in 2006 gave a new depth of 175m (574feet).[5]
A unique ecosystem of crabs and limpets has been described on the flanks of the volcano.[7]
It was first named as Ruby Volcano in the 1973 paper that described some of the 1966 eruption evidence.[8]