Eruption that Formed New Japan Island Continues Rumbling on

By Masakatsu Shimizu / Yomiuri Shimbun Staff Writer

13:17 JST, November 22, 2023

An undersea volcanic eruption that created a new island about 1 kilometer south of Iwoto Island was continuing as of Nov. 16, The Yomiuri Shimbun has confirmed.

Explosions on the new island were visible every few minutes from a Yomiuri Shimbun plane that flew over Iwoto on the day.

As of Nov. 10, the new island was about 400 meters long from its north tip to the south, and about 200 meters from east to west. A Yomiuri reporter on the plane observed at least seven explosions while circling over the island for about 25 minutes.

Volcanic ash and rocks were mixed in among the plumes of black smoke that spewed out of a cone-shaped crater and reached heights of about 200 meters. White steam also blanketed parts of the island, and the nearby seawater had turned a cloudy greenish color. Some material ejected during the eruption was floating on the water’s surface.

According to University of Tokyo Associate Prof. Fukashi Maeno, an expert on volcanic geology, the blasts seen on Nov.16 appeared to be phreatomagmatic explosions that occur when hot magma interacts with water. Those explosions show that magma is intermittently rising underground.

“There are also signs that lava has flowed out on the island,” Maeno said. “If this activity continues, the new island could remain for a long time.”

Iwoto is part of the Ogasawara island chain that is administered by the Tokyo metropolitan government.