Nine months after a new volcanic island broke through the surface of the western Pacific Ocean and merged with the existing island of Nishimo-shima 600 miles south of Tokyo, the combined island is still giving off smoke as it grows 200,000 cubic meters in volume per day, thanks to lava flow. (That’s enough to fill 80 Olympic-sized swimming pools.)

The birth of a new island might seem like a pretty cool thing, but there are a few distinct downsides.

"If lava continues to mount on the eastern area, it will be deposited on steep slopes," University of Tokyo scientist Fukashi Maeno explained in an email to NASA’s Earth Observatory website. "This could cause instability on the slope, so a partial collapse of the island may occur. We need to carefully observe the growth process."

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Maeno told Agence France-Presse that if the new hybrid island collapses, it could unleash a tsunami upon nearby inhabited areas as it does, He calculated that seismic waves from 12 million cubic meters of collapsing volcanic rock would create a tsunami that would send three feet of water slamming into the nearby town of Chichijima and its 2,000 inhabitants within minutes at bullet-train speed.

An official from the Japan Meteorological Agency, which monitors earthquakes and tsunamis in addition to weather, told AFP that the agency’s scientists already are monitoring the island.

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"We studied the simulation this morning, and we are thinking of consulting with earthquake prediction experts… about the probability of this actually happening, and what kind of measures we would be able to take," the official told AFP.

There's also apparently the possibility that the island could explode. According to Asahi Shimbun, Japan Coast Guard officials say that a cone-shaped mound of congealed lava inside a volcanic vent there could seal off movement of magma and raise interior pressure within the island, which might eventually result in a large-scale explosion.

Photo: A rapidly-growing new island in Japan could possibly collapse and cause a tsunami, or else explode, a scientist warns. Credit: Japan Coast Guard