"A cluster of rhyolitic lava domes and associated pyroclastic deposits form the small 4 x 6 km island of Kozu-shima in the northern Izu Islands. Kozu-shima lies along the Zenisu Ridge, one of several en echelon ridges oriented NE-SW, transverse to the trend of the northern Izu arc. The youngest and largest of the 18 lava domes, 574-m-high Tenjo-yama, occupies the central portion of the island. Most of the older domes, some of which are Holocene in age, flank Tenjo-yama to the north, although late-Pleistocene domes are also found at the southern end of the island. Only two possible historical eruptions, from the 9th century, are known. A lava flow may have reached the sea during an eruption in 832 AD. Tenjo-san lava dome was formed during a major eruption in 838 AD that also produced pyroclastic flows and surges. Earthquake swarms took place at Kozu-shima during the 20th century."  -Smithsonian Volcano Archive
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