Detecting seafloor lava flows with seafloor roughness

Abstract

Much of the seafloor is currently unexplored. As such, increasing the number of options in the “tool box” is vital for studying the oceans. This study uses the North Arch Volcanic Field, an area of seafloor north of Hawaii partially covered with lava flows and seamounts, as a case study to evaluate the usefulness of an additional tool to explore the seafloor and its features - roughness. This location was previously mapped using GLORIA side-scan sonar, yielding a lowresolution image of the area, revealing abnormally large lava flows. This study surveyed a portion of the North Arch Volcanic Field, creating a high-resolution map of the area with a 30 kHz Kongsberg multibeam echo sounder aboard the R/V Thomas G. Thompson. By creating an algorithm to calculate roughness values based on bathymetric data, a second map of the area was created that was compared with the collected bathymetry data and high resolution sub-bottom seismic profiles to determine if roughness can be used to identify lava flows. To do this, it was hypothesized that there will be an increase in roughness at lava flows and lava boundaries compared to surrounding sediment. Results show that roughness can be a useful tool to identify and emphasize the structure of lava flows and may reveal features of interest that bathymetry alone may miss. It is important to note that the roughness algorithm will enhance error in the bathymetric data, particularly those at the edges of swaths that arise from ship roll. Roughness may be an important parameter in future artificial intelligence algorithms to aid in finding features of interest in large bathymetric data sets.