Reconstructing the tephra dispersal pattern from the Bronze Age eruption of Santorini using an advection–diffusion model

Abstract

The advection–diffusion model TEPHRA2 has been used in conjunction with the downhill simplex method (DSM) and one-at-a-time (OAT) inversion methods to reconstruct the eruption conditions and seasonality consistent with the deposit patterns from the Bronze Age (‘Minoan’) eruption of Santorini. We investigated three datasets representing different depositional environments (proximal terrestrial, distal terrestrial and deep-sea core), in order to determine source conditions such as plume height, erupted mass and grain-size and recreate the tephra fall deposit from the Plinian, co-ignimbrite and combined eruptive phases. The results of the DSM and OAT method agreed adequately well with each other for erupted mass, plume height and grain-size distribution. Both approaches were able to successfully recreate the Plinian deposit but estimating conditions that created the co-ignimbrite and deep-sea core dataset were less successful. The reduced agreement is the result of the low quantity (6 to 28 deposit points) and quality (inconsistent deposit depths at localities adjacent to each other) of the datasets, and the different dynamics between co-ignimbrite and Plinian columns, with the former not well represented in the model. Different sampling methods between archaeological and volcanological disciplines and post-depositional processes which have acted on the tephra deposits since the Bronze Age can explain the discrepancy between these computed and observed deposits. The seasonality of the Minoan eruption was investigated by using seasonal wind profiles for winter, spring, summer and autumn. We find that the Bronze Age eruption of Santorini is likely to have during the spring and summer months with a main dispersal axis aligned East. Crete would have received very little ash fall, and the eruption would not have caused much disruption to the life of the inhabitants of the island.