It was in November last year that Decoded Science reported on the emergence of a volcanic island, then unnamed, in the Ogasawara, or Bonin, Islands in the western Pacific Ocean hundreds of miles south of the main Japanese archipelago.
Such islands, we noted “don’t necessarily have a lot of staying power – if the eruption falters then the chances are that the newly-erupted material will erode fairly quickly. If the volume of erupted material continues to accumulate, however, the Bonin Islands could find themselves with a new companion – and the Pacific’s notorious Ring of Fire will have another active volcano”.
Niijima/Nishinoshima A Year On
Well, the island now has a name. It’s on its second name, in fact; originally (in one sense if not in another) known as Niijima, which means ‘new island’, it now goes under the name of Nishinoshima — actually the name of an adjacent volcanic island with which it has merged.
Nishinoshima is itself not exactly a geological Methuselah; it barely broke the surface of the ocean until it also grew as a result of an eruption as recently as 1973.
As the island is still erupting its impossible to say how big it currently is. It certainly grew very quickly as the result of the eruption of Niijima; the Global Volcanism Program reported that in March 2014: “Niijima was still expanding outward in all directions from the vents, and that Nishinoshima had grown to over three times its original size.”
More recently, news reports suggest that, a further eight months on, the merged islands are much bigger. “According to the Japan Coast Guard, the new islet’s size as of Oct. 16 was 1.85 square kilometers, about 185 times the 0.01 square kilometers when it first appeared,” reported the Asahi Shimbun website on 13 November.
“The total size of Nishinoshima island, including the new islet that joined it, is about 1.89 square kilometers, or 8.6 times its size before the eruption, according to the Coast Guard,” it went on.
New Islands Emerging
Of course, islands such as Nishinoshima are a long time a-building, even if they only become news when they breach the surface and become ‘proper land.’
The Bonin Islands are a typical example of a volcanic chain, formed when the subduction of one plate beneath another leads to melting of the subducted crust at depth. The molten rock rises and reaches the surface as a volcano.
The planet has many, many examples of volcanic island chains, including the Aleutians, the Kuril Islands and the main Japanese archipelago itself, each of whose islands will have broken the surface in the same way as Nishinoshima.
While typical of subduction zones, new volcanic islands are not exclusively found there. The Icelandic island of Surtsey emerged spectacularly from the sea in 1963, giving its name to explosive emergent eruptions worldwide, which are now known as Surtseyan.
And the Hawaiian island chain, formed by the movement of the Pacific plate over a magmatic ‘hot spot’, is awaiting the birth of its own new island, the submarine volcano Lo’ihi, which will in time break the surface and become land.
Most ‘new’ volcanos are underwater but there are exceptions. Most famously, the volcano we know know as Paricutin, appeared with little or no warning in the middle of a Mexican cornfield.
In the words of the farmer who witnessed this extraordinary event: “I noticed that a crack, which was situated on one of the knolls of my farm, had opened . . . and I saw that it was a kind of fissure that had a depth of only half a meter… it was then I saw how, in the hole, the ground swelled and raised itself 2 or 2.5 meters high, and a kind of smoke or fine dust — grey, like ashes — began to rise up in a portion of the crack that I had not previously seen.”
Nishinoshima Rising: The Future
Whether, in the context of its merger with its neighbour, we can truly say that Nishinoshima is a new island is probably open to debate.
Either way, it’s clear that the eruption is ongoing and it’s reasonable to suppose that the merger of the infant volcano and its neighbour is likely to add yet more to Earth’s land area in the future.