Nikko submarine volcano has two summit cones within the remnant of a large circular caldera, which has been subsequently filled by eruptive material. The CTD tow-yo detected hydrothermal venting from the summit of the volcano. The data were collected using the EM300 multibeam system mounted on the hull of the R/V Thompson. The grid-cell size is 35 meters. The image is not vertically exaggerated.
