New oceanic crust forms along the mid.ocean ridge axis by a complex interplay of magmatic, tectonic, and hydrothermal processes. These processes are known to vary significantly along the axis, as manifested by the division of the ridge into segments bounded by transform faults and overlapping spreading centers. Hydrothermal venting along the mid.ocean ridge is a first.order process that is responsibe for much of the heat loss from the ridge axis. This project will determine the distributions, relative intensity, and first.order chemical characteristics of hydrothermal venting along the morphologically, geophysically, and pertologically well.known segments of the East Pacific Rise between 9 03N and 11 10N by surveying the water column for hydrothermal plumes. This section of the ridge was chosen because it is well.studied, and because it encompasses portions of mid.ocean ridge with high magma supply as well as portions that are magmatically starved.