The Gulf of California is widening and deepening as the Baja Peninsula and mainland of Mexico are spreading apart, resulting in a series of tectonic spreading centers and transform faults. At the mouth of the gulf lies the Alarcon Rise and just within the gulf is the Pescadero Basin, where MBARI discovered new hydrothermal vent fields in 2012 and 2015, respectively. During those expeditions and other multi-disciplinary cruises since, the entire spreading axes were mapped at 1-m resolution with our Mapping AUVs, the Auka vent field in the southern Pescadero Basin was mapped at centimeter-scale resolution with the Low-Altitude Survey System, and fluids, deposits, and organisms were sampled from ROV Doc Ricketts. Separated from each other by only about 70 km and a transform fault, the vent fields on the Alarcon Rise are classic black smokers: metal-sulfide spires populated with chemosynthetic fauna similar to those found on the East Pacific Rise far to the south, while the vent fields in the Pescadero Basin are completely different: enormous mounds of white carbonate venting clear fluids and populated with animals more similar to the Guaymas Basin far to the north. This difference is due not to distance but to the different chemistries of the fluids: thick sediments filling the Pescadero Basin have modified the hydrothermal fluids rising from below, whereas the Alarcon Rise hydrothermal vent fields are located on bare lava flows. The Seafloor Mapping Lab and our collaborators continue to investigate the tectonics, biogeochemistry, microbiology and ecology of hydrothermal vent fields of the Pescadero Basin and intend to expand that work to other spreading basins of the Gulf of California.




Vega-Ramirez, L.A., R.M. Spelz-Madero, R. Negrete-Aranda, F. Neumann, D.W. Caress, D.A. Clague, J.B. Paduan, J. Contreras, and J.G. Peña-Dominguez. 2021. A new method for fault-scarp detection using linear discriminant analysis in high-resolution bathymetry data from the Alarcon Rise and Pescadero Basin. Tectonics, 40(12): 1–18.

Negrete-Aranda, R., F. Neumann, J. Contreras, R.N. Harris, R.M. Spelz, R. Zierenberg, and D.W. Caress. 2021. Transport of heat by hydrothermal circulation in a young rift setting: Observations from the Auka and JaichMaa Ja'ag' vent field in the Pescadero Basin, southern Gulf of California. Journal of Geophysical Research: Solid Earth, 126(8): 1–20.  

Clague, D.A., D.W. Caress, B.M. Dreyer, L. Lundsten, J.B. Paduan, R.A. Portner, R. Spelz-Madero, J.A. Bowles, P.R. Castillo, R. Guardado-France, M. Le Saout, J.F. Martin, M.A. Santa Rosa-del Rio, and R.A. Zierenber. (2018). Geology of the Alarcon Rise, Southern Gulf of California. Geochemistry Geophysics Geosystems, 19: 807–837.

Paduan, J.B., R.A. Zierenberg, D.A. Clague, R.M. Spelz, D.W. Caress, G. Troni, H. Thomas, J. Glessner, M.D. Lilley, T. Lorenson, J. Lupton, F. Neumann, M.A. Santa Rosa del Rio, and C.G. Wheat. 2018. Discovery of hydrothermal vent fields on Alarcón Rise and in Southern Pescadero Basin, Gulf of California. Geochemistry, Geophysics, Geosystems, 19: 4788–4819.