Pliocene–Pleistocene Deep-Sea Volcanoes in the Northwest Pacific

Abstract

We show that volcanic activity was occurring in the NW Pacific seafloor areas adjacent to Japan, the Kuril Islands, Kamchatka, and the Commander Islands during Pliocene to Pleistocene time. The activity was highest in two areas. At least three major volcanoes originated and were active in the southern area behind the Japan trench off Honshu and Hokkaido. Lava-dominated Pleistocene stratovolcanoes originated and were active in the Detroit and Wayne volcanic massifs in the central area, on the Detroit rise, which is the northern termination of the Emperor Ridge. As well, there was a large (42 km across) volcano-tectonic structure that was previously unknown, viz., a deep-sea calderoida. Somewhat north where the margin of the Obruchev Rise is adjacent to the deep-sea Kamchatka trench, a volcano (?) was active during Pliocene time whose present-day summit is at a height of –713 m. We show that the Detroit Seamount rise is a seafloor block that was uplifted in the Pliocene in the form of a horst and showed Pliocene–Pleistocene volcanic activity.