These images represent aspects of a towed hydrocast (tow-yo) at NW Rota-1 submarine volcano, located at 14° 36' N. The tow-yo was performed February 12, 2003. A) The bathymetric map shows (in white) the tow line of hydrocast. B) The hydrothermal plume above volcano shown as delineated by optical backscatter. The black saw-tooth pattern is the track of the CTD-rosette package as it passed over the volcano. The stair-step features in the track as are the locations where samples were taken . ΔNTU= nepelometric turbidity units above ambient seawater.