A recent undersea volcanic eruption has led to the formation of a new isle off the coast of Iwo Jima, about 1,200 kilometers south of Tokyo, Japanese researchers have said.
Part of the Ogasawara Islands, the new isle consists mainly of rock masses formed north of the eruption site. It could grow larger if volcanic activity continues, according to the Earthquake Research Institute at the University of Tokyo.
Setsuya Nakada, a professor emeritus of volcanology at the University of Tokyo, said magma has been erupting underwater — known as a phreatomagmatic eruption — for some time around Iwo Jima, with the magma solidifying as rock below the surface.
But after an eruption on Oct. 30, the solidified magma that has been piling up started to break the surface, causing the new isle to form, said Nakada, who flew over the site on Friday.
“In an earlier stage, a vertical jet of black color, debris — which is a solidified magma — and water gushed upward,” Nakada said. “Since Nov. 3, the eruption started changing and the emission of volcanic ash continued explosively.”
The isle, which consists of piles of pumice, erodes easily. However, as long as the volcanic activity continues, the chance that the isle will remain is high, as lava flow will help protect it, Nakada said.
“The areas that don't have lava could be scraped away. So if more and more lava comes out, and covers the area, I think that part will remain forever,” Nakada said, adding that it remains uncertain whether the eruption will continue.
Nakada added that the way the isle emerged resembles how another new island formed in 2013, which eventually merged with Nishinoshima, an island located in the Ogasawara chain.
Nishinoshima was also created from an underwater volcanic eruption, eventually growing to about 2 kilometers in diameter.
“There is a possibility that the (new) island could merge with Iwo Jima if the eruption continues,” Nakada said.
According to the Meteorological Agency, volcanic tremors have been detected on Iwo Jima every few minutes since around Oct. 21, followed by eruptions off the southern coast.
Iwo Jima is an active volcano to the south of Ogasawara Island. It is also about 60 km north of the Fukutoku-Okanoba underwater volcano, which had a major undersea eruption in 2021.
In July 2022, a magmatic eruption was recorded for the first time off the southeastern coast of Iwo Jima, along with a phreatomagmatic eruption. That was followed by another eruption in June and another one in October.
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