The majority of volcanic activity on Earth occurs beneath the sea yet the mechanisms of submarine eruptions remain poorly understood due to the lack of direct observations of the events and their products. One of the most peculiar and rarely observed submarine eruption styles is the production of giant gas-filled floating lava bombs from relatively shallow water eruptions of basaltic magma. These eruptions can pose hazards to ships at sea and to island and coastal communities due to the explosive release of gas and the high temperature of the magma. This research investigates shallow submarine volcanic eruptions that produce large floating scoria blocks, also known as lava balloons. The 1891 submarine eruption of Foerstner volcano off the northwest coast of Pantelleria island in the Mediterranean Sea will serve as a type example of this style of activity. High-resolution bathymetric mapping and video recording of the seafloor vent site and samples of rocks and volcanic sediments will be used in the analysis and are already in-hand from a previous oceanographic expedition. The mapping and video data will be used to create the first high-resolution geologic map of the vent area associated with this style of submarine volcanism. A major goal of the work will be to inform models of submarine explosive eruptions, which, at present, are immature compared to those for subaerial eruptions due to the lack of direct seafloor observations and paucity of studies on submarine deposits. Another objectiveis to address the fundamental problem of eruptive mechanisms via direct examination of the nature and morphology of the seafloor deposits left by the explosive Foerstner eruption. Major and trace element geochemical analyses of lava and volcaniclastic samples from the eruption will be carried out on bulk rock samples using XRF. The composition of associated quenched volcanic glass will be analyzed via electron microprobe. Data will be used to characterize the geochemical nature of the magma erupted and assess its volatile content and implications for eruptive mechanisms. Magma compositions at the vent site will be compared with samples of other submarine volcanic cones in the area to evaluate whether compositions can be used to fingerprint individual vents. Fourier transform infrared spectroscopy (FTIR) will be used to examine the composition of melt inclusions trapped in olivine and clinopyroxene crystals in order to determine pre-eruption magma gas (H2O and CO2) content and evaluate its role in driving the explosive nature of the eruption. The research will examine whether pre-concentration of volcanic gases in sub-seafloor conduits results in the build up of gas to levels that allow magma to inflate to the extent that it buoyantly rises to the sea surface. This research on the mechanisms of shallow water submarine explosive volcanism will allow for better assessment of its impacts on marine ecological disruptions and the acidification of local seawater. Broader impacts include undergraduate and graduate student support and development of educational modules used into university courses taught by the investigator, as well as support of an institution from an EPSCoR state.
