Tonga

In this earlier satellite view of the islands of Hunga Tonga and Hunga Ha'apai from 14 November 2006, the healthy vegetation appears bright red and Hunga Ha'apai is significantly smaller in size than in the previous image. Photo courtesy of NASA.

In mid-March 2009, a plume of ash and gas burst out of the ocean as an undersea volcano began to erupt in the South Pacific nation of Tonga. Small sections of the rim of the large volcano had been above water, forming the islands of Hunga Tonga and Hunga Ha'apai (center). The eruption occurred at two vents, one submerged and the other on Hunga Ha'apai. The eruption pumped out enough rock and ash that by 25 March, when NASA's Terra satellite captured this image, the submerged vent was surrounded by new land. The new land is the dark mass south of Hunga Ha'apai. It was not present in an earlier image taken on 14 November 2006 (next photo). In this image, clouds cover the space between the new land and Hunga Ha'apai, but the new land connects Hunga Ha'apai with the underwater vent, essentially enlarging the small island. The vent itself is the nearly perfectly circular hole near the southern edge of the new land. Also revealed are some of the other impacts of the eruption. The ocean around the erupting volcano is bright blue, likely colored with ash, rock, and other volcanic debris. The eruption killed or damaged plants on Hunga Ha'apai. In this false-color image, plant cover is red. In 2006, Hunga Ha'apai had supported vegetation, but after the eruption, the island was black. Either the plants were buried in ash or dead in the wake of the eruption. Photo courtesy of NASA.

August 2006 brought two new things to the Tonga Islands in the South Pacific. One was a raft of lightweight, frothy volcanic rock - pumice - floating on the ocean surface. The other was a new island emerging out of the water. NASA's Aqua satellite captured the aftermath of the eruption on 10 August 2006. For comparison, the bottom image shows the same area but taken almost one year earlier, on 15 September 2005. The emerging volcanic island is partially hidden by its own plume. Volcanic plumes often appear drab gray or beige compared to clouds, and plumes from the emerging island move away from it in different directions, one to the southeast, and some to the north. The bright white spot directly over the island may be cloud cover, or it could be steam resulting from volcanic emissions. The raft of pumice appears to the northeast of the emerging island, and it actually connects, via a thin thread, to neighboring Late Island. The blue-green color of the water around the raft and the new island is probably fine sediment that is making the deep blue water more reflective. The pumice raft gained international attention when a news report described the experience of a yacht crew that inadvertently encountered the pumice raft. The "sea of stone" clogged the yacht's engine-cooling system, forcing the vessel to turn back. Pumice rafts are not an everyday occurrence, but they have been observed before. Biologists theorize that pumice rafts may be one of the ways that plants and animals spread from island to island in marine environments. Photo courtesy of NASA.