2004 towyos at NW Rota-1 submarine volcano. The hydrothermal plume over the summit of the volcano is apparent, as well as a deep plume that extends down to 2000 meters water depth, and possibly deeper because the signal is still strong at that depth. Bathymetry and CTD data were collected in 2003 and 2004 on the Submarine Ring of Fire cruises to the Mariana Arc. The scale bar at the top left corner of the image indicates the nephelometric turbidity units, an optical measurement of the particles in the water, which indicates the location and intensity of the hydrothermal plume. The image is two times vertically exaggerated.