Sentry-mounted Sidescan Sonar Imaging of Kermadec Arc Volcanoes


Co-funded by DOEI and Access to the Sea: 2011


Volcanic arcs are the surface expression of subduction related magmatism.  Intraoceanic arcs – those built upon oceanic crust – with a submarine component total 22,000 km in length, ~1/3 the length of the global mid-ocean ridge (MOR) system.  Submarine arcs produce isolated volcanoes/seamounts with greater potential for explosive eruptions than MOR volcanoes.  The shallow depth and sediment-free summits of many arc volcanoes make them important oases for chemosynthetic and benthic animal communities and fisheries.  In addition, submarine arc volcanoes host long-lived and robust hydrothermal circulation that produces the largest mineral deposits preserved in the rock record.  Arc mineral deposits are richer in precious metals (Gold, Silver) than those on MORs, and with their shallow depths and position along the margins of the ocean basins, mining of these deposits is likely to become economically viable in the coming decades.  This proposed work seeks to evaluate the relationship between explosive and effusive volcanic eruptions, regional and local faulting, and hydrothermal discharge to volcano development and seafloor mineralization at three Kermadec Arc volcanoes.  To do so, I will utilize the first near-bottom sidescan sonar data ever collected on arc volcanoes.  These sidescan sonar data, along with co-located subbottom profile data and seafloor photographs, will allow me to identify the size, type (explosive/effusive), and relative age of volcanic deposits, sedimentary deposits, and faulting on the volcano summits and flanks.  The level of detail (sub-meter resolution) and coverage (volcano summits and flanks) provided by these data are unique for arc volcanoes and fill a crucial gap in our knowledge between large-scale arc volcano morphology and highly localized submersible observations.  Construction of detailed geologic maps will allow me to test hypotheses regarding volcano growth, caldera development, and subsequent hydrothermal discharge localization proposed for arc volcanoes that have significant implications for the modes of mass and heat transfer and chemical exchange at convergent margins.

This proposal will facilitate my collaboration with NDSF on the development of processing and acquisition best-practices for the new AUV-based sidescan sonar system.  Several proposals, including one of my own, were submitted to the most recent NSF panel to use this pending capability of Sentry.  The success of theses and future proposals for Sentry-based sidescan sonar mapping will depend on a demonstration of the effective use of these sensors in real-world settings, which is an important goal of this research.   This work also represents collaboration with Institute of Geological and Nuclear Science (GNS - New Zealand) scientists with whom WHOI has recently (2010) signed a memorandum of understanding and who have strong scientific and national interests in the Kermadec Arc.  This project will investigate a small, but important data set that will open new avenues of seafloor exploration for arc volcanoes and lead to future proposal development with GNS colleagues for investigating magmatic and hydrothermal processes in the Kermadec Arc.