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Report on Kavachi (Solomon Islands) — July 2007

Bulletin of the Global Volcanism Network, vol. 32, no. 7 (July 2007)
Managing Editor: Richard Wunderman.

Kavachi (Solomon Islands) Vigorous upwelling, discolored water, and minor explosions in April 2007

Please cite this report as:

Global Volcanism Program, 2007. Report on Kavachi (Solomon Islands). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 32:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200707-255060.

Volcano Profile |  Complete Bulletin


Kavachi

Solomon Islands

8.991°S, 157.979°E; summit elev. -20 m

All times are local (unless otherwise noted)


A large earthquake (M 8.1) occurred in the Solomon Islands on 2 April 2007, centered about 126 km NW of Kavachi. Following the earthquake, Corey Howell of The Wilderness Lodge on Gatokae Island received several reports from residents on Gatokae and Vangunu Islands describing noises attributed to Kavachi (~ 35 km WSW of Gatokae). A confirmed report from Marila Timi of Biche Village (on the S coast of Gatokae) stated that around the time of the 2 April earthquake, Kavachi emitted an eruption column visible from her garden above the village.

On 6 April Howell traveled to Kavachi to observe the volcano. Howell spent 2.5 hours on location within 200 m of the active vent, and dove down to within tens of meters of the vent. The volcano exhibited its usual vigorous upwelling, producing a plume of discolored mud- and sulfur-laden water several hundred meters wide and at least 3 km in length downcurrent (figure 9). He measured a temperature of 40°C in the subsurface plume, which appeared normal as compared with his previous 30 visits to Kavachi since 1999. The only explosive activity observed or felt was occasional thudding detonations and sea-surface percussions, with shockwaves producing spray and billows of ash-laden water (figures 10 and 11). Kavachi lacked a significant explosive eruption column or signs of ejected pyroclastic materials, behavior witnessed on many previous visits. On this visit, Howell found nothing out of the ordinary following the 2 April earthquake.

Figure (see Caption) Figure 9. Photograph showing a mud-and sulfur-laden plume downcurrent of Kavachi's upwelling vent on 6 April 2007, forming a discolored area several hundred meters wide and several kilometers long. Howell noted that such plumes are frequently seen at Kavachi. Courtesy of Roy Hall (posted on The Wilderness Lodge website).
Figure (see Caption) Figure 10. Some of the stronger activity observed at Kavachi on 6 April 2007 included very turbulent ash-laden water above the vent, explosive and percussive noises, and discolored water downcurrent of the vent. Courtesy of Roy Hall (posted on The Wilderness Lodge website).
Figure (see Caption) Figure 11. Some of the stronger activity observed above the vent at Kavachi on 6 April 2007 consisted of shockwaves producing dancing spray, accompanied by staccato bursts of sound. These noises also reverberated through the bottom of the boat. Courtesy of Roy Hall (posted on The Wilderness Lodge website).

Geologic Background. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island about 30 km N of the site of subduction of the Indo-Australian plate beneath the Pacific plate. 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: Corey Howell, The Wilderness Lodge, Peava Village, Gatokae Island, Western Province, Solomon Islands (URL: http://thewildernesslodge.org/).