Home Reef Erupts in the Southwest Pacific Ocean
The underwater volcano has again created a small island.
In the southwest Pacific Ocean, a seafloor ridge with the highest density of underwater volcanoes in the world stretches from New Zealand to Tonga. On September 10, 2022, one of these underwater volcanoes awoke. Since then, the Home Reef seamount in the Central Tonga Islands has repeatedly ejected plumes of steam and ash, oozed lava, and discolored the surrounding water.
Eleven hours after the eruption first began, a new island rose above the water surface. The Operational Land Imager-2 (OLI-2) on Landsat 9 captured this natural-color view (see image above) of the young island on September 14, 2022, as plumes of discolored water circulated nearby. Previous research suggests that these plumes of superheated, acidic seawater contain volcanic rock fragments, particulate matter, and sulfur.
The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga Plates started about 4–5 million years ago. Currently, the eastern boundary of the Tonga Plate is one of the fastest subduction zones, with a rate up to 24 centimeters (9 inches) per year. The trench formed between the Kermadec-Tonga and Pacific Plates is also home to the second deepest trench in the world, at about 10,800 meters (35,400 feet), as well as the longest chain of submerged volcanoes.
On September 14, researchers with Tonga Geological Services estimated the area of the island to be 4,000 square meters (43,000 square feet / 1 acre) and the elevation to be 10 meters (33 feet) above sea level. By September 20, the island had grown to cover 24,000 square meters (258,000 square feet / 6 acres). The new island is located southwest of Late Island, northwest of Mo‘unga‘one, and northeast of Hunga Tonga-Hunga Ha‘apai.
Home Reef sits within the Tonga-Kermadec subduction zone, an area where three tectonic plates are colliding at the fastest converging boundary in the world. The Pacific Plate here is sinking beneath two other small plates, yielding one of Earth’s deepest trenches and most active volcanic arcs.
Islands created by submarine volcanoes are often short-lived, though they occasionally persist for years. Home Reef has had four recorded periods of eruptions, including events in 1852 and 1857. Small islands temporarily formed after both events, and eruptions in 1984 and 2006 produced ephemeral islands with cliffs that were 50 to 70 meters (160 to 230 feet) high. An island created by a 12-day eruption from nearby Late‘iki Volcano in 2020 washed away after two months, while an earlier island created in 1995 by the same volcano remained for 25 years.
“The volcano poses low risks to the aviation community and the residents of Vava‘u and Ha‘apai,” the Tonga Geological Service said in an update issued on September 20. “All mariners are, however, advised to sail beyond 4 kilometers away from Home Reef until further notice.” The service noted that most ash should fall within a few kilometers of the vent.
NASA Earth Observatory image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey.