In late December, an undersea volcano in the Polynesian island kingdom of Tonga began erupting. About 60 kilometers (40 miles) north of Tongatapu, the two small islands of Hunga Tonga and Hunga Ha'apai sit atop a large seamount. These volcanic islands stand just 128 and 149 meters (420 and 490 feet) above sea level. The new eruption seems to be occurring just offshore of Hunga Ha'apai, though details are scarce so far.
According to news reports, fishermen spotted signs of an eruption on December 19, and a photographer on the island of Tongatapu observed steam plumes on the horizon on December 24. Dense cloud cover prevented other remote observations for several days.
This true-color image from December 29, 2014, shows the waters around Tonga, Hunga Tonga, and Hunga Ha'apai, as observed on by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. A white plume rises into the sky over Hunga Ha’apai, in the north of the image. Local news outlets said the plume extended 3 kilometers (2 miles) into the sky. The discolored water that seems to originate at Hunga Ha’apai and flow southward suggests an underwater release of gases and rock or the disturbance of sediment by the eruption.
Hunga Ha'apai is part of the Tonga-Kermadec volcanic arc and is part of the very active Pacific Ring of Fire. The last reported eruption occurred in 2009.