A once-hidden Japanese volcano is rising up out of the Pacific Ocean. A new study in thejournal Geology has outlined the remarkable evolution of one of the world’s youngest islands, revealing how it formed in two incredibly explosive phases.
Roughly 1,000 kilometers (620 miles) south of Tokyo lies the island of Nishinoshima, a volcanic island that was first seen erupting in 1973. This piece of rock is the tip of a much larger underwater volcano, one that is about 3 kilometers (1.86 miles) high and perhaps 94 kilometers (58.4 miles) in circumference at its base.
In November 2013, explosive volcanic activity was observed to the southeast of the island; huge lava outflows were seen rising up to the surface of the ocean, and within a month the new island rose 25 meters (82 feet) above sea level. By the end of the year, the new volcano and the older, larger Nishinoshima had fused in a fiery embrace.
After observing the island’s birth, the authors of this new study have revealed that its formation occurred in two main stages. The first involved the sudden release of hot, broiling lava into the shallow, cold water. An envelope of steam rapidly formed along the margins of the lava, before explosively expanding into the water and dramatically propelling glassy molten blobs high into the air.
This is known as a “Surtseyan” eruption, named after the Icelandic island that formed in precisely the same way back in 1963. Within three days of discovering the island, the Japanese Maritime Self-Defense Force noticed that the eruption style changed.