First Speleothem Evidence of the Hiera Eruption (197 BC), Santorini, Greece

Speleothems are useful in detecting past geoenvironmental events. Variations in trace element concentrations may constitute a diagnostic of volcanic eruptions, enabling both dating and environmental impact assessment. This work attempts to detect possible ‘signatures’ of past volcanic eruptions in speleothems from Zoodochos Pigi cave on Santorini. Higher-than-usual concentrations of elements and minerals (e.g. barium and monazite respectively) exotic to typical speleothem chemistry in a band within a flowstone retrieved from the cave were revealed through SEM-EDS and XRD analyses and thought to be of volcanic origin. By chance, charcoal trapped in the said speleothem band allowed dating to establish the timing of the volcanic event. The radiocarbon date pointed towards the historically documented Hiera eruption, the earliest of a series of volcanic eruptions that postdate the Minoan eruption. The Hiera eruption, although less violent than the Minoan eruption, signallised the recrudescence of intracaldera activity which culminated in the formation of Palea Kameni (197 BC) with palpable effects on the regional environment. The interpretation of the results presented here, i.e. geochemical analysis on speleothems and radiocarbon dating, are cross-correlated with the well-documented timeline of eruptions of Santorini and ancient literature.