As lava continues to flow out of a new volcanic island rising out of the Pacific Ocean, scientists worry that it could trigger a tsunami off the coast of Japan.
The small, but growing, island ("Niijima" in Japanese) appeared just nine months ago and quickly merged with the already-existing island of Nishimo-shima, located 600 miles south of Tokyo.
It now covers 1.39 square kilometers (0.54 square miles), and thanks to increasing daily lava flows, it grows 200,000 cubic meters in volume per day - that's enough to fill 80 Olympic swimming pools.
While the birth of a new island may seem cool, scientists worry about the island's ever-increasing size.
"If lava continues to mount on the eastern area, it will be deposited on steep slopes," University of Tokyo scientist Fukashi Maeno explained to NASA's Earth Observatory. "This could cause instability on the slope, so a partial collapse of the island may occur. We need to carefully observe the growth process."
Maeno told the Agence France-Presse (AFP) that if the new hybrid island collapses, it could unleash a tsunami upon nearby inhabited areas. He calculated that a rockfall of 12 million cubic meters of lava would generate a tsunami that would send three feet of water towards the island of Chichijima and its 2,000 inhabitants at bullet-train speed.
An official from the Japan Meteorological Agency, which monitors earthquakes and tsunamis in addition to weather, told the AFP that the agency's scientists are already monitoring the island.
"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," he said.
There's also apparently the possibility that the island could explode - due to a mound of congealed lava inside a volcanic vent on the north side of the island - but the Coast Guard says no such eruption is imminent, according to NASA.
Japan's north-east was devastated by a huge tsunami in March 2011, caused by a massive undersea earthquake, killing more than 18,000 people and destroying towns.