Submeter bathymetric mapping of volcanic and hydrothermal features on the East Pacific Rise crest at 9°50′N

Abstract

Recent advances in underwater vehicle navigation and sonar technology now permit detailed mapping of complex seafloor bathymetry found at mid‐ocean ridge crests. Imagenex 881 (675 kHz) scanning sonar data collected during low‐altitude (∼5 m) surveys conducted with DSV Alvin were used to produce submeter resolution bathymetric maps of five hydrothermal vent areas at the East Pacific Rise (EPR) Ridge2000 Integrated Study Site (9°50′N, “bull's‐eye”). Data were collected during 29 dives in 2004 and 2005 and were merged through a grid rectification technique to create high‐resolution (0.5 m grid) composite maps. These are the first submeter bathymetric maps generated with a scanning sonar mounted on Alvin. The composite maps can be used to quantify the dimensions of meter‐scale volcanic and hydrothermal features within the EPR axial summit trough (AST) including hydrothermal vent structures, lava pillars, collapse areas, the trough walls, and primary volcanic fissures. Existing Autonomous Benthic Explorer (ABE) bathymetry data (675 kHz scanning sonar) collected at this site provide the broader geologic context necessary to interpret the meter‐scale features resolved in the composite maps. The grid rectification technique we employed can be used to optimize vehicle time by permitting the creation of high‐resolution bathymetry maps from data collected during multiple, coordinated, short‐duration surveys after primary dive objectives are met. This method can also be used to colocate future near‐bottom sonar data sets within the high‐resolution composite maps, enabling quantification of bathymetric changes associated with active volcanic, hydrothermal and tectonic processes.