Kavachi volcano is a shallow submarine volcano located south of the remote Vangunu Island in the Solomones. It is als known as Rejo te Kvachi, "Kavachi's Oven", and one of the most active of the Pacific with near surface eruptions every few years that often build temporary islands. New islands were formed at least 9 times since its first recorded eruption during 1939. The new islands formed were not large enough and coated with solid lava flows to be able to resist wave erosion. They were submerged again after a few months after each eruption. The frequent shallow submarine eruptions that sometimes breach the surface produce surtseyan activity, magma-water explosions that eject jets of steam, ash, and incandescent bombs above the sea surface. On some occasions during such eruptions, the vent was sealed sufficiently to produce liquid lava spattering and lava flows on the temporary islands.

Kavachi volcano is only about 30 km north of the subduction of the Indo-Australian plate beneath the Pacific plate and close to a regional spreading center.

The volcano has produced mainly basaltic-to-andesitic eruptions. It often formed new islands up to 1 km long. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, which suggests that earlier eruptions had breached the surface as well.

Kavachi is roughly conical and rises from a depth of 1.1-1.2 km on the north and greater depths to the south.