"The elongated island of Nii-jima, SSW of Oshima, is 11 km long and only 2.5 km wide. It is comprised of eight low rhyolitic lava domes that are clustered in two groups at the northern and southern ends of the island, separated by a low, flat isthmus. The flat-topped domes give the island the appearance of two large plateaus bounded by steep cliffs. The Mukai-yama complex at the southern end of the island and Achi-yama lava dome at the northern end were formed during Nii-jima's only historical eruptions in the 9th century AD. Shikine-yama and Zinai-to domes form small islands immediately to the SW and west of Nii-jima, respectively, during earlier stages of volcanism. Earthquake swarms occurred at Nii-jima during the 20th century."  -Smithsonian Volcano Archive
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