Niijima, a new volcanic island that appeared in November 2013, has merged with the neighbouring island of Nishinoshima, another volcanic island which last erupted in 1973, according to NASA. When the new island initially appeared it was 500 m from Nishinoshima, and it was thought that it would probably be a short-lived structure, produced by a single bout of volcanism, then washed away over the following few years. But Niijima has now expanded and completely engulfed Ninioshima, and is apparently here to stay.
Satellite image of Nishinoshima and Niijima captured by NASA's Earth Observing 1 on 8 December 2013. Earth Observatory.
Satellite image of Nishinoshima and Niijima captured by NASA's Earth Observing 1 on 24 December 2013. Earth Observatory.
Image of the new, combined island taken on 30 March 2014. Earth Observatory.
Nishinoshima and Niijima lie on he boundary between the Pacific and Philippine Plates, where the Pacific Plate is passing beneath the Philippine Plate as it is subducted into the Earth. As the Pacific Plate is subducted it is melted by the heat and pressure of the planet's interior. The lighter fractions of this melted material then rise through the overlying Philippine Plate as magma, fueling the volcanoes of the various islands and island groups that lie along the boundary.
The approximate position of the new island. Google Maps.
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