Nishinoshima: The Mysterious Island

Nishinishima is one of the recently formed Islands (latest one is Shelly Island) in Japan that formed in two explosive phases. It is situated off the southern coast of Japan. As per a 2016 report, the Nishinoshima island is 2.7 square km in size and 100 m high.

                                           Fig.1: Location map of Nishinoshima Island. © Google Earth

The Island was formed by “Surtseyan” and “Strombolian” eruptions that took place in 1973 and 2013. Surtseyan is a common phreatomagmatic volcanic eruption that takes place in shallow oceans. Strombolian eruptions are relatively mild explosions that drive out incandescent cinder, lapilli, and lava bombs to a  height of tens to a few hundreds of meters.

Satellite images at different intervals from the WorldView-2 satellite courtesy of DigitalGlobe were used for quantitative analysis of the eruption and formation of the Island. Satellite technology is employed because the island is inaccessible and dangerous to visit due to volcanic eruptions.

The Island was first noticed in 1973 when the underwater volcano erupted with shooting mounds of molten andesitic lava and was named Nishinoshima. Forty years later, in 2013, about 400 m southeast of the Nishinoshima Island, an eruption took place with Surtseyan-type of eruptions and formed a cone in a shallow sea at 20 m depth and of 150*80 m in size. Later the eruption changed into Strombolian because a pyroclastic cone formed around the vent and prevented external water from running into the crater and formed a small islet termed as Niijima.  In late December 2013, the new islet merged with the existing Nishinoshima.

               Fig. 2: Shows how the small islet merges into Nishinoshima Island at different intervals. © Google Earth

As per recent updates, the island is still spewing out 80 Olympic-sized swimming pools worth of lava every single day and outbreaks from the volcano keep adding land. Scientists see this island as a rare chance to examine how life begins to colonize the bare earth. Even though it's nearly all bare rock formed from the cooling lava, scientists believe that one day the island will be humming with plants and possibly animals too.

                                           Fig. 3: View of Nishinoshima Island on December 31, 2013. © DigitalGlobe

Summary

Satellite imageries of WorldView-2 were used to analyse the newly formed Island, created by Surtseyan and Strombolian volcanic eruption in 1973 and 2013. A plume of smoke stemming from the eruption is also observed.  Outbreaks from the volcano keep adding land and scientists see this island as a rare chance to examine how life begins to colonize the bare earth.