(CNN) — A NHK video shows how a remote island volcano in Japan is rapidly growing by spewing lava in multiple layers.
A drone equipped with a 4K ultra high-definition camera was flown over Nishinoshima Island by NHK.
The island in the Ogasawara chain, about 1,000 kilometers south of Tokyo, began to expand after an undersea eruption started near it in 2013.
Nishinoshima has now grown more than 12-fold.
The area within a four-kilometer radius of the island’s center is a no-entry zone due to the eruption.
But the unmanned helicopter made it possible to film the volcano from the comparatively low altitude of about 2,300 meters.
The video shows a crater in the island’s center continuously spewing smoke in a spiral. Rocks up to three meters across are being thrown into the air.
Dark lava flowing from the mountainside produces steam as it hits the sea water.
Footage taken at night gives an even clearer image of the lava flows. The flowing lava shines brightly and looks like a river streaming from the mountain. Some of the lava went underground before reappearing near the coast.
Tokyo Institute of Technology Professor Kenji Nogami analyzed the footage. He says new lava flows were formed on top of old ones that hardened after cooling. This apparently helped the land to become thicker.
The Japan Coast Guard says Nishinoshima Island is about two kilometers wide north to south as well as east to west and has a total surface area of 2.72 square kilometers.