Volcanic Island’s Explosive Growth Creates New Land

In the Pacific Ocean some 600 miles south of Tokyo, the volcanic island Nishinoshima is undergoing a “vigorous growth spurt,” according to NASA’s Earth Observatory. The young volcanic island has been very active since mid-June, belching enough ash and lava to grow its southern shore by at least 500 feet between June 19 and July 3, reports the Japan Broadcasting Corporation (NHK).

The uninhabited island is 80 miles from the nearest populated area and is part of the more than 30 land masses in the Ogasawara Islands, a UNESCO World Heritage Site. The island, the tip of a massive submarine volcano, was barely more than 2,000 feet wide until eruptions beginning in 1973 formed several new islets that eventually coalesced, according to the Smithsonian Institution’s Global Volcanism Program and Volcano Discovery.

Then, in 2013, another new islet gurgled into existence near Nishinoshima, billowing white clouds of steam as seawater cooled its molten lava, transforming it into new land. The islet was prolific: in 2014 the Japan Times reported that enough lava had issued forth from the infant landmass to fill the Tokyo Dome six times.

The prodigious eruptions repeated the cycle of the 1970s eruption, melding Nishinoshima with its neighbor. The merger saw the island grow to twelve times its original size between 2013 and 2015, reported Japan Today at the time.

Intermittent eruptions have continued to enlarge Nishinoshima’s footprint since then, but, as the Japan Coast Guard noted, volcanic activity surged in late May of this year. On June 29 an aerial survey by Japan’s Coast Guard spotted black smoke and magma erupting from the central crater, according to NHK.

On July 3, the ash plume rose to 15,400 feet above sea level, and the next day the volcano launched ash to altitudes of 24,000-28,000 feet—the highest plume since the volcano emerged from dormancy in 2013, reports Shuichi Abe of the Mainichi. According to the Mainichi, the Japan Meteorological Agency (JMA) is warning any nearby sea vessels of the volcano’s activity, which has fired volcanic bombs more than a mile from the crater.

Smithsonian geologist Elizabeth Cottrell noted the tiny island provided quite a nice Fourth of July display with "ash plumes rising 8.3 km (about five miles) above the summit and gas from the volcano reaching Alaska," she says.

Kenji Nogami, a volcanologist at the Tokyo Institute of Technology who has been keeping tabs on Nishinoshima since 2013, tells NHK that the volcanic island is positioned squarely above a huge reserve of underground magma. He says this means lava will likely continue to flow, further increasing the island’s size.

"The little island has grown considerably during the present eruption—exciting to be sure, but in the arc of geologic time, this is typical," says Cottrell. "In fact, nearly all of the islands of the western pacific are volcanic, including the entire archipelago of Japan. It’s just a reminder that every new continent begins with a bang like the one we are seeing now at Nishinoshima.”

Alex Fox | | READ MORE

Alex Fox is a freelance science journalist based in California. He has written for the New York Times, National Geographic, Science, Nature and other outlets. You can find him at Alexfoxscience.com.