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Far-travelled ash megaturbidite fed by shoreline-crossing pyroclastic currents from the Kos Plateau Tuff eruption. IODP Expedition 398, Hellenic Arc Volcanic Field

^^Tim Druitt^1^, Abigail Metcalfe1, Katharina Pank2, Steffen Kutterolf2, Jonas Preine3, Karim Kelfoun1, Christian Hübscher4, Paraskevi Nomikou5, Thomas Ronge6, and IODP Expedition 398 scientists.

  • Affiliations:  1University Clermont-Auvergne, Laboratoire Magmas et Volcans, Clermont-Ferrand, France; 2GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany; 3Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole MA, USA; 4Institute of Geophysics, University of Hamburg, Hamburg, Germany; 5Department of Geology and Geoenvironment, National and Kapodistrian University of Athens, Athens, Greece; 6International Ocean Discovery Program, Texas A&M University, College Station TX, USA. 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 79

  • Programme No: 6.2.15

  • Theme 6 > Session 2

Abstract

Explosive eruptions from island volcanoes deliver huge quantities of ash to the marine environment. While many of the transport pathways are understood, those from shoreline-crossing or submarine pyroclastic currents, and the water-supported gravity flows into which they transform, are not. We report the discovery during IODP Expedition 398, of an ash megaturbidite up to 200 m thick buried deep in the rift basins of the South Aegean Volcanic Arc. The 80 cubic km of ash derives from the 161 thousand-year-old Kos Plateau Tuff (KPT) caldera-forming eruption 120 km to the east, as shown by offshore-onshore chemical correlation of glasses and minerals. The marine ash forms a chemically homogeneous graded bed that lacks internal bioturbation. This implies an emplacement time of less than the several months to years typically required for seabed re-population by burrowing organisms. We propose that the ash bed sedimented from a stream of eruption-fed turbidity currents that travelled westwards 120 km from the Kos eruptive center down arc-parallel slopes to the rift basins. These basins at the time were deep bathymetric troughs that captured the Kos-derived turbidity currents, allowing great thicknesses of ash to accumulate far from the eruption source. The megaturbidite increases the total erupted volume of the KPT eruption to >200 cubic km (uncompacted), suggesting that eruption volumes for other island or coastal explosive eruptions may also be underestimated. The study highlights how large volcanic eruptions re-mould sea floor landscapes, lay down ash megabeds, and destroy seafloor biota on island-arc-wide scales in short-lived, catastrophic events.