If I am counting right this will be the birth of the fourth island in under two years. Two in Jebel Al-Zubair, one in Indonesia (that I for the life of me can’t remember the name of) and now Nishinoshima is in the process of birthing its second island in 40 years. It is also interesting that it takes place within a week of the fiftieth anniversary of the birth of Surtsey.
But first off, it is not the volcanic caldera island of Nishinoshima that is erupting, it is the volcanic caldera island of Nishinoshima that is erupting! Confused? Me too!
The non-erupting Nishinoshima is a part of the Oki Islands in the Korea Sea, that Nishinoshima is part of a Somma volcano that used to be a massive stratovolcano, beside it is the remnant of the Dogojima stratovolcano. Both the destroyed Somma-volcano and the Dogojima is situated within yet another caldera structure (Dozen). For now, let us leave this volcanically highly interesting part of the world and go to the erupting Nishinoshima.
The Erupting Nishinoshima
Nishinoshima (Rosario Island) was a very small island (700 square meters) out in the Volcano Islands arc. It is the surfacing top of a massive seamount rising 4 100 meters from the Ogasawara Trough on the east side and 2 600 meters from the oceanic plateau that surrounds the other sides. Situated on top of the seamount is a large submerged caldera 15 by 9 kilometers. Nishinoshima is surrounded on all sides by cones, vents, pillars and parasitic seamounts.
1973 – 1974 Island birth
On the 30th of May a passing ship noticed that Nishinoshima was ejecting pillars of white smoke reaching a height of approximately 100 meters every few minutes. During overflights the next day it was noticed that the eruption was taking place 400 meters east of the old Nishinoshima Island. A second flight revealed an active Jacuzzi at the eruption site and a belt of floating pumice and discolored water stretched five kilometers away. The second flight also noticed two black rocks sticking out of the water.
During the next 9 months a new island grew next to Nishinoshima, the island was never named, something that might have been a lucky stroke, because after the eruption ended on the first of March in 1974 waves quickly moved the erupted material around so that the new island connected with the old much smaller Nishinoshima. The new Island was 700 by 250 meters, but diminished in size over the coming years. The eruption was rated a VEI-2.
Before this eruption it was believed that Nishinoshima had not erupted for 10 000 years, this claim is very dubious since both the old and the new island is consisting mainly of cinder, tuff and pumice intermixed with lava flows. It is more likely that Nishinoshima has followed a pattern of birth, erosion, re-birth since the caldera forming eruption took place 10 000 years ago.
After that eruption there have been several suspected eruptions, but none that broke the surface. Two of those have a higher order of likelihood and that is the 1978 eruption 6.5 kilometers northwest of the island and another in north, west and south of the island in 1980 that caused widespread water discoloration.
Earlier today the Japanese Meteorological Agency announced that they had confirmed that an island forming eruption is taking place 500 meters southeast of Nishinoshima Island.
The Japanese Air Force detected an ash plume at 10 in the morning, and at 4 in the afternoon the Japanese Coast Guard confirmed that there was an eruption and the formation of a circular 200 meter wide island.
According to the Japanese authorities there is a high likelihood of a long eruption since this would seem to be the pattern from the previous eruptions that lasted from 9 months up to two years.
The authorities warn all ships to stay clear of the caldera. The eruption will if it continues probably produce a mix of cinder cones and lava flows binding.