Temporal variation in the morphology and structure of the axial summit caldera and young volcanic flows, and relationship to hydrothermal venting on the East Pacific Rise crest 9 30-51'N - Fornari, D J; Perfit, M R; Smith, M; Haymon, R M; Edwards, M H; Cochran, J R; Coakely, B; Von Damm, K L; Lilley, M (EOS, Transactions, American Geophysical Union, 1994)