Last June the Tonga Islands, a chain of 150 or so islands located northeast of New Zealand--and right where the Pacific tectonic plate slams into the Australian plate--added one more to their number, at least temporarily. This island emerged from a volcanic eruption that began on June 6 on a submerged shoal; by early July, when the eruption had stopped, it was about 900 feet wide and 140 feet high. Researchers don’t know, however, how long the world’s newest chunk of land will stay around. There have been six island-forming eruptions in recorded history at this site, says Brad Scott, a volcanologist with the Institute of Geological and Nuclear Sciences in New Zealand, and the first researcher to glimpse the baby island, and all of those islands eroded away eventually. The longest-lasting island braved the ocean waves for 17 years; the shortest, which was composed of ultralight pumice, lasted but three weeks. This one has a lava dome and should stick around for a while, Scott says, but it still appears likely that it will suffer the same fate.