The formation of the island was captured through imagery taken by the Landsat 9 satellite on September 14. A vast plume of steam and ash drifts away from the volcano in the image. Previous studies suggest that these superheated, acidic seawater plumes contain sulfur, volcanic rock fragments, and particulate debris.
The baby island continues to grow
Volcanoes that are submerged in water are known as seamounts. When underwater volcanoes erupt, the lava erupts to form an undersea ridge. Layers of lava build until a ridge breaks the sea’s surface to form an island.
Initially, Tonga Geological Services experts estimated the baby island to be 4,000 square meters (1 acre) in size and 13 feet (10 meters) above sea level. However, it had grown to 24,000 square meters (6 acres) by September 20.
“The volcano activity poses low risks to the Aviation Community and the residents of Vava’u and Ha’apai,” said Tonga Geological Services. “No visible ash in the past 24 hours was reported. All Mariners are advised to sail beyond 4km away from Home Reef until further notice.” The service noted that most ash should fall within a mile or so of the vent.
The new island can be found southwest of Late Island, northeast of Hunga Tonga-Hunga Ha’apai, and northwest of Mo’unga’one. This part is known as the Tonga-Kermadec subduction zone, where three tectonic plates collide at the fastest global converging boundary. The Pacific Plate here is sinking beneath two other small plates, yielding one of Earth’s deepest trenches and most active volcanic arcs.