PRESENT-DAY MAGMATIC, TECTONIC AND HYDROT HERMAL ACTIVITY ON THE EASTPACIFIC RISE BETWEEN 17-DEGREES-S AND 19-DEGREES-S (NAUDUR CRUISE)

The submersible-study of four segments of the East Pacific Rise betwee n 17 degrees and 18 degrees 40'S, where the spreading rate is greater than 150 mm/a, allows us to confirm the variability of the accretion p rocesses. The segment between 17 degrees and 17 degrees 30'S shows an intense present-day magmatic activity. The one between 18 degrees 10' and 18 degrees 22'S shows a mainly tectonic activity. The segment betw een 18 degrees 22' and 18 degrees 37'S is an intermediate stage with a n axial graben in which fresh lavas were emplaced by an extremely youn g eruption. On all the segments the hydrothermal activity exists rangi ng from shimmering water up to black smokers, It is associated with di fferent stages of animal colonization.