Presentation by Sue DeBari.
MARINE TEPHRA RECORDS TELL BIG STORIES—HIGHLY EXPLOSIVE VOLCANISM AND RIFTING IN PARADISE (THE HELLENIC ARC, GREECE)
The Hellenic arc in Greece is the most active volcanic region in Europe, posing hazards that range from tephra fall to pyroclastic flows that travel across both the seafloor and the sea surface, and resulting tsunamis. The most famous eruption in the Christiana-Santorini-Kolumbo (CSK) volcanic field within this arc is the 1600 BCE caldera-forming eruption of Santorini that buried a thriving Bronze Age city and caused widespread tsunamis. The most recent explosive eruption is the ~400-year-old eruption of neighboring Kolumbo volcano, but islands within the Santorini caldera have erupted as recently as 1950. The CSK volcanic field sits within an active submarine extensional basin whose sediments preserve the entire tephra record of the arc since its initiation. IODP Expedition 398 sampled this uninterrupted record of volcanism at twelve sites within the volcanic field, providing an unprecedented opportunity to develop a robust record of hazardous events for volcanic risk assessment. We are also sampling the crystal cargo in particularly noteworthy tephra events to develop conceptual models for magma storage regions and eruption triggers, and how those have changed over time. The record is also being used to decipher long term links between volcanism and tectonics.
There are many exciting and sobering outcomes of Expedition 398, including the recognition of a previously unknown submarine explosive eruption of ancestral Santorini based on our sampling of giant offshore pumice deposits. This submarine deposit volume is six times bigger than the late Bronze Age Santorini eruption, the largest in the region. Pyroclastic flow deposits reached land 30km away. Another previously unknown tephra deposit within Santorini’s caldera provides evidence for an explosive eruption from Kameni volcano in 726 CE. Effusive eruptions from this caldera volcano are well known as recently as 75 years ago, but this VEI 5 eruption exceeds previously considered worst-case scenarios. Other notable expedition outcomes include good matches between seismic and petrologic models for Kolumbo volcano magma storage, the recognition of a far-traveled ash megabed originating from the Kos Plateau >120km away, and documented linkages between crustal faulting/rifting events and volcanism.
