Known as Fukutoku-Okanoba, the volcano has risen above the sea surface three times since it was first observed in 1904, but eventually disappeared within two years due to wave erosion.
In 1914, the volcano had reached about 1,000 feet in height with a circumference of about 7.5 miles.
Tokyo Institute of Technology Professor Kenji Nogami told The Yomiuri Shimbun that a seabed upheaval in 1999 significantly reduced the water depth above the volcano, meaning that the current activity could form a permanent island.
According to coast guard officials, the volcano’s latest unrest spewed ash and smoke about 300 feet into the air, and the surrounding water changed to a yellowish-green color while other parts became a cloudy gray.
Photos: Japan Coast Guard