Asia Dive News : Undersea volcanic eruption sends vapor plume 1,000 meters skyward

Authorities confirmed Sunday that a column of vapor observed the day before off Minami-Iwojima Island in the Pacific Ocean had been caused by an eruption of an undersea volcano.

The column of water vapor -- 1,000 meters high and 50 to 100 meters thick -- was observed at around 5:45 p.m. Saturday about 5 km northeast of the uninhabited island, according to a report received by the Defense Agency.

The Japan Coast Guard issued an international warning for vessels to stay away from the area, which lies some 1,400 km south of Tokyo, and launched an aerial survey Sunday morning.

"It's highly likely that it's caused by an eruption of an underwater volcano," coast guard spokesman Shigeyuki Sato said of the strange occurrence. "A similar eruption occurred in the area before."

Previous eruptions of the volcano were observed in 1986 and 1992.

An island rose at the site of the volcano due to the eruption in the early 1900s. But the island -- named Shin-Iwojima -- later eroded into the sea.

There was no tsunami risk following the suspected eruption, the Meteorological Agency said.

The vapor was spotted by a Maritime Self-Defense Force member stationed at the air base on Iwojima Island.

Minami-Iwojima is located about 50 km south-southeast of Iwojima Island. Both are part of the Ogasawara chain.

The water in the area has become yellowish brown over a 1-km area due to the eruption, the coast guard said.

Coast guard aircraft crews on Sunday returned with video images of the vapor plume and surrounding water, Sato said. The survey crew also found gray mud rising from the bottom. It was not immediately known if volcanic gases were being released.

Coast guard aircraft halted their survey after less than two hours due to unspecified safety concerns but planned to return as early as Monday for further monitoring, Sato said.

The color of the sea water had begun changing in mid-May, the Defense Agency said.

An MSDF helicopter confirmed Saturday that the center of the steam column was reddish, the agency added.