Brett Dennis-Duke: Backscatter Analyses as a Means of Determining Lava Morphology

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For this project, I am looking to illuminate the connection between backscatter patterns and ground morphology at the ASHES hydrothermal field region of the Axial Seamount, Juan de Fuca Ridge. The geography and geology of this area are currently under close examination, as these properties will directly affect placement of cables and nodes for the Regional Scale Nodes Cabled Observatory (as funded by the National Science Foundation’s Ocean Observatories Initiative).

“Backscatter” occurs when the sonar waves that are used to track bathymetry are reflected off the seafloor and are received back at their source. Generally, this is considered to be background noise and is filtered out, but since these patterns are directly influenced by the composition, size, and texture of the material from which they are being reflected, they can also be used to diagnose the physical character of the surfaces being analyzed. In this study, I will be examining the backscatter data collected by the multibeam sonar RESON equipment on the ROV Jason and comparing distinguishable backscatter patterns to a geological map of varied lava morphologies and ground textures. This map will be constructed using the COVE (Collaborative Ocean Visualization Environment) program to overlay morphological data (as determined by digital imagers collected during the RECON portion of the same survey) on a bathymetric map of the region. Should distinct patterns be identified and correlated to specific ground morphologies, these backscatter patterns could serve as a useful diagnostic tool for mapping the varied terrains of the Axial Seamount and could greatly simplify the process prospecting potential sites of node and cable emplacement.