<p>Erupting from an undersea <a id="guy8" title="volcano" href="http://environment.nationalgeographic.com/environment/natural-disasters/volcano-profile.html">volcano</a> some 745 miles south of <a id="z-f9" title="Tokyo, Japan" href="http://travel.nationalgeographic.com/travel/city-guides/tokyo-japan/">Tokyo</a>, smoke and ash rise roughly 30 stories into the air in this image captured by a <a id="t26y" title="Japan Coast Guard" href="http://www.kaiho.mlit.go.jp/e/index_e.htm">Japan Coast Guard</a> helicopter on February 3, 2010.<br><br>The helicopter's mother ship, <em>Yashima,</em> 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 <a id="exze" title="Japan Meteorological Agency" href="http://www.jma.go.jp/jma/indexe.html">Japan Meteorological Agency</a>.<br><br>"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.&nbsp; "It is very dangerous to approach the area as it is impossible to predict further eruptions."<br><br>(Related: <a id="y0q:" title="&quot;Giant Undersea Volcano Found Off Iceland.&quot;" href="http://news.nationalgeographic.com/news/2008/04/080422-iceland-volcano.html">"Giant Undersea Volcano Found Off Iceland."</a>)</p><p><em>—Julian Ryall in Tokyo</em></p>

Monster Rises From Japanese Seas

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."

(Related: "Giant Undersea Volcano Found Off Iceland.")

—Julian Ryall in Tokyo

Photograph courtesy Japan Coast Guard

Undersea Volcano Erupts, May Form New Island

Spewing ash and smoke some 30 stories above the sea, a submarine volcano erupting off Japan could eventually form a new island.

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