Geophysical and petrological boundaries on mid-ocean ridges provide ideal locations to study the relationships between magmatic, tectonic, and hydrothermal processes. Alvin-based observational data and geochemical data for basalts and hydrothermal fluids are used to investigate these relationships at an axial discontinuity on the East Pacific Rise (EPR) crest between ~9°36´N and 9°38´N. This ridge-crest discontinuity is morphologically expressed by the overlap of an eastern and western axial summit collapse trough (ASCT) that delimits the primary volcanic and hydrothermal loci along the ridge crest in this area. The ASCTs overlap by ~3 km and are offset in a right-lateral sense by 0.45 km. Near-bottom imaging of this area in 1989 and 1991 shows changes in volcanic morphology and increases in hydrothermal and biological activity consistent with the occurrence of a magmatic event during that time interval. When combined with the inferred age and structure of the seafloor, basalt geochemistry, and hydrothermal fluid chemistry, these temporal changes suggest active southward propagation of the eastern ASCT and show that the western ASCT was unaffected by the recent magmatic event. Numerous extinct hydrothermal vents and older-looking lava flow surfaces suggest waning of magmatic activity in the western ASCT.