Erupting from an undersea volcano some 745 miles south of Tokyo, smoke and ash rise roughly 30 stories into the air in this image captured by a Japan Coast Guard helicopter on February 3, 2010.
The helicopter's mother ship, Yashima, was on a routine patrol when the Fukutoku-Okanoba volcano exploded. There had been no warning that an eruption was imminent, according to Keiji Doi, senior coordinator for seismic information at the Japan Meteorological Agency.
"Coast Guard vessels and aircraft are now collecting data in the area," Doi said, adding that other ships have been warned to keep their distance. "It is very dangerous to approach the area as it is impossible to predict further eruptions."
During a lull in the Fukutoku-Okanoba eruption on February 3, some of the waters above the undersea volcano bubble and take on yellowish green colors, while others are cloudy with displaced sand and grit.
"This is a volcano that is active fairly frequently, and we have minor events as many as several times a decade," Doi said. The last Fukutoku-Okanoba eruption occurred in July 2005.
The February 3 submarine-volcano eruption took place about 3 miles (4.8 kilometers) north-northeast of volcanic South Iwo Jima (pictured). The island is part of Japan's Bonin Islands, which also include famous World War II battle site of Iwo Jima, some 37 miles (60 kilometers) north of South Iwo Jima.
During previous Fukutoku-Okanoba eruptions, lava has broken the sea surface, creating islands—the same basic process that created the Hawaiian Islands. But waves have always quickly washed away any Fukutoku-Okanoba islands, preventing them from becoming anything more than short-lived lava mounds.
As for the February eruption, said Doi, of the Japan Meteorological Agency, "We have seen no evidence of an island being created yet, but it is possible, and we will continue to monitor the situation."
Discolored water stains the sea surface in the wake of the February 3 undersea-volcano eruption off Japan.
Fukutoku-Okanaba is believed to have erupted seven times since 1904, when its activities were first recorded. On three of those occasions, temporary islands were formed, but all later sank below the surface again.
The most recent of the volcano's short-lived additions to Japan's Bonin archipelago was born on January 18, 1986, although the island disappeared by March 8 of that same year.
The island that resulted from a 1914 Fukutoku-Okanaba eruption was about five miles (eight kilometers) wide and was nearly a hundred stories tall. That island lasted more than two years.
At around 7:45 a.m on February 3, 2010, the Yashima crew, on a routine survey, first noticed smoke coming from the surface of the ocean (pictured) near South Iwo Jima, according to Japan Coast Guard spokesperson Tomoyuki Suzuki. The smoke was the crew's first sign that something big was brewing.
In addition to noticing the smoke, the crew heard the blast and "felt" the pressure of the initial blast, Suzuki said.
The Yashima is continuing to monitor the site, he said, but the crew is keeping a safe distance, as the emissions include poisonous gases, including sulphur dioxide and carbon dioxide (volcano safety tips).