New island emerges after undersea volcano erupts off Japan, but experts say it may not last long

Undersea volcano off Japan's Iwo Jima erupts, forming tiny new island. Volcanic activity has since subsided, island may not last long due to its "crumbly" formation. Similar eruptions in past led to formation of new islands. Japan sits on Pacific "ring of fire," Iwo Jima site of WWII's fiercest fighting.

An undersea volcano erupted off Japan three weeks ago, providing a rare view of the birth of a tiny new island, but experts say it may not last very long.

The unnamed undersea volcano, located about 1 kilometre (half a mile) off the southern coast of Iwo Jima, which Japan calls Ioto, started its latest series of eruptions on Oct. 21.

Within 10 days, volcanic ash and rocks piled up on the shallow seabed, its tip rising above the sea surface. By early November, it became a new island about 100 metres (328 feet) in diametre and as high as 20 metres (66 feet) above the sea, according to Yuji Usui, an analyst in the Japan Meteorological Agency's volcanic division.

Volcanic activity has increased near Iwo Jima and similar undersea eruptions have occurred in recent years, but the formation of a new island is a significant development, Mr. Usui said.

Volcanic activity at the site has since subsided, and the newly formed island has somewhat shrunk because its “crumbly” formation is easily washed away by waves, Mr. Usui said.

He said experts are still analyzing the development, including details of the deposits. The new island could survive longer if it is made of lava or something more durable than volcanic rocks such as pumice.

“We just have to see the development,” he said. “But the island may not last very long.”