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Nishinoshima Island, Ogasawara Tokyo Aerial photograph. Tokyo, that is part south shore yim the Volcano Islands arc.
Originally, the above-water part of the ridge of an underwater caldera, Nishinoshima was enlarged in 1974 after fresh eruptions created a new section of the island. Another eruption that began in November 2013 further enlarged the island and attracted worldwide attention. As of 2016, the island was about 2. There were further eruptions in 2017, 2018, and in 2019-2020. As of 14 August 2020, it is about 4. The island was named “Rosario Island” when it was discovered by the Spanish ship Rosario in 1702. During the early stages of the 2013 eruption, a new volcanic island was formed southeast of the original Nishinoshima.
Government officials said the island would be named “after it is stable and it is clear it will remain”. As the island has now merged with Nishinoshima, “there is little possibility it will be named as a separate entity. Prior to 1974, Nishinoshima was a small, green island which had no eruptions in the past 10,000 years. The upper part of the bay is the old island, and the lower part is the new island formed by the 1973 eruption. Later, the bay was filled with sediment due to sedimentation, forming a trapezoidal coastline just before the eruption in 2013. Another crew discovered that two black rocks were rising from the sea.
In July, the eruption continued to erupt water fountains every few minutes with white smoke rising to 100 m above sea level. In November, a fissure eruption was noted on the new island with a chain of cinder cones running from southwest to northeast. The most recent cones were formed at the end of the chain, with the original cone being destroyed by the waves. In December, the new island grew larger than “old” Nishinoshima. A small craterlet on the new island was also emitting lava flows. By February 1974, the new island had developed two cinder cones at the western end of the new island, but only the eastern cinder cone was erupting.
Observations on 11 January noted that the active eastern cinder cone was emitting a lava flow. Lava flows were still erupting from the new island’s flanks. On 1 March, the five cinder cones were quiet, but a large lava flow may have still been effusing from the island’s flanks. Nishinoshima as of 8 December 2013. The land from the eruption grew rapidly in less than two weeks. Nishinoshima as of 2014 July 4. It becomes even larger, and the relatively white old island is slightly visible.
In November 2013, an eruption created a new small island south-southeast off the shore of the original island. The newer portion of the island is now larger than the original Nishinoshima landmass. During July and August 2014, lava flow increased, causing the island to expand rapidly to the east. Between September and December, the lava flow increased further and headed north, almost completely overrunning the pre-existing island, leaving only a small portion of the old island exposed. On 27 December 2014, Japanese authorities said the island had reached nearly 2. The eruption continued throughout the first half of 2015, and the island continued to expand.
However, by August, the volcano ceased to erupt smoke and ash, but continued to emit lava. As of 16 September 2015, the total area of the island had decreased slightly, but the fumarolic zone had expanded as “vigorous volcanic activity continued without significant change”. In October 2016, a team of scientists visited Nishinoshima to conduct research on the island. Apart from documenting the island’s ecology and geology, monitoring equipment was also installed for future volcanic activity.
