Kavachi is a submarine volcano in the SW Pacific located in the Solomon Islands south of Gatokae and Vangunu Islands. Its first recorded eruption occurred in 1939 and has since produced many ephemeral islands up to 1 km long where lava flows were occasionally observed. Volcanism has been characterized by phreatomagmatic explosions that ejected steam, ash, and incandescent bombs. The current eruption period began in October 2021 and more recently has consisted of discolored water plumes (BGVN 48:03). This report covers similar activity of discolored water plumes during February through July 2023 based on satellite imagery.

Natural color satellite imagery showed occasional discolored (light yellow-green) submarine plumes on clear weather days that generally originated from a single point during each month of the reporting period (figure 29). The discolored water drifted or extended in different directions with every observation. One yellow-green discolored plume was visible on 14 February that drifted N for several kilometers (figure 29). Four discolored plumes were visible on 16, 21, 26, and 31 March; on 21 March the yellow-green color was notably intense and showed ripples in the surface of the water near the point of origin (figure 29). It extended for several kilometers to the NW. Plumes were visible four times during 5, 20, 25, and 30 April; on 20 and 25 April there was a small circle of milky brown discolored water at the point of origin and the plume extended SW and S, respectively. Faint discolored water was visible on 30 May, though much of it was obscured by weather clouds. Two discolored plumes were observed on 4 and 14 June and three were faintly visible on 4, 9, and 29 July.

Figure 29. Natural color satellite images showing light yellow-green discolored plumes of water originating from Kavachi on 14 February 2023 (top left), 21 March 2023 (top right), 25 April 2023 (bottom left), and 14 June 2023 (bottom right). The plumes varied in intensity, length, and direction, though they all originated from a single point, which was characterized by a more translucent, milky color to it. Courtesy of Copernicus Browser.

Geological Summary. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is located in the Solomon Islands south of Vangunu Island. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Information Contacts: Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).