Kavachi is one of the most active underwater volcanoes in the Pacific Ocean. Located in the Solomon Islands and named after the sea god of the Gatokae and Wangun people, this conical seamount rises approximately 1,200 meters (3,900 feet) above the seafloor. But its summit remains only 20 meters (65 feet) below sea level, making it easier for satellites to detect changes in the color of the water due to volcanic activity than at deeper underwater volcanoes.

Volcanic activity and observation

According to the Smithsonian Institution’s Global Volcanism Program, Kawachi has erupted at least 39 times since 1939; The latest boom period starts in 2021. In 2024, the volcano continued to erupt and satellites continued to capture images of colorless puddles.

The image above, obtained by the OLI (Operational Land Imager) on Landsat 8 on March 8, shows a discolored water cloud near an underwater volcano. The plume moved north-northeast towards Ngatokae Island. Wangunu Island, pictured, is about 24 kilometers (15 miles) north of Kawachi, while Papua New Guinea is about 800 kilometers (500 miles) to the west.

The MODIS Spectroradiometer (Moderate Resolution Imager) aboard NASA’s Terra and Aqua took images of similar underwater clouds near Kawachi several times in recent weeks, including February 3, 15, and 23.

Scientific studies and results

Previous studies have shown that such superheated acidic water clouds may contain solid particles, volcanic rock fragments, and sulfur, as well as deposits of silicon, iron, and aluminum oxides. The color of the feather can give clues about the composition of the particles within it. Blonde and brown feathers tend to have higher percentages of iron, while white feathers tend to have higher percentages of silicon or aluminum.

Although Kawachi has been difficult for scientists to access, a lull in activity allowed one group to explore it in 2015. Researchers observed layers of orange and white bacteria in the crater, as well as marine life including silky and hammerhead sharks, bluefin fish and snappers.

Other active underwater volcanoes — the Wailului seamount in American Samoa and the Columbus in Greece — have highly acidic water and “kill zones” that contain the carcasses of larger animals, the discovery report’s authors noted. “It is likely that the high crater walls at these locations caused physical trapping and concentration of vent fluids, whereas the Kawachi crater is relatively shallow and exposed to strong surface currents that allow rapid mixing,” they wrote in the report.

Geological context and features

Kawachi formed in a tectonically active region just 30 kilometers (18 mi) northeast of the subduction zone. The volcano produces lava ranging from basalt, rich in magnesium and iron, to andesite, which contains more silica. It is known for its phreatomagmatic eruptions, where the interaction of magma and water shoots steam, ash, volcanic rock fragments, and red-hot bombs from the water into the air.