It's surprising that something like this goes on unnoticed, and but for a satellite view, no one would be the wiser.
Murray Ford was scanning satellite imagery of a young island in Tonga called Hunga Tonga-Hunga Ha’apai when he noticed something odd—a turquoise plume of water—in the corner of an image. The coastal geologist from the University of Auckland had stumbled across an underwater volcano in the midst of an eruption.
“It may continue for some days or weeks, and an island may form temporarily,” said Martin Jutzeler, a University of Tasmania geologist who studies underwater eruptions. “However, new volcanic islands are easily eroded by wave action.”
Underwater eruptions are relatively common in this area, which is part of the Tonga-Kermadec volcanic arc and the Pacific Ring of Fire. This plume appears to have originated from a seamount that geologists call “Submarine Volcano III.” It has shown signs of activity in 1911, 1923, 1970, 1990, and 2007.