Characterization of juvenile pyroclasts from the Kos-Nisyros Volcanic center (Aegean Arc)

Approximately 160,000 years ago, one of the largest explosive volcanic eruptions of the last two million years occurred on the eastern Mediterranean island of Kos, during which ~60 km3 of volcanic ash and pumice were emplaced as pyroclastic fall and flow deposits over an area >2,000 km2. In comparison to the Minoan eruption, which created a 12-km diameter caldera on the nearby island of Santorini, and which may have had a large negative impact on Minoan civilization, the Kos Plateau Tuff (KPT) was almost an order of magnitude larger in volume. Although the repose periods for such volcanic systems are on the order of 1,000-100,000 years (increasing with increasing volume), similarly cataclysmic eruptions will occur again in the Mediterranean basin and elsewhere, with devastating consequences on a regional or even hemispheric scale.

Whether a volcanic eruption of viscous magma occurs as a (relatively slow) effusion of lava or as a highly hazardous explosive burst of hot gases and volcanic particles depends primarily on how the magma behaves in the conduit prior to reaching the earth’s surface. If the conditions are such that bubble expansion is rapid, the magma may reach fragmentation, the process by which viscous, bubbly magmatic foam disintegrate into a low-viscosity particle-laden hot gas. Understanding how magma ascends in conduits and how it fragments is therefore fundamental to predict the consequences of the eruption at the earth’s surface.

By characterizing the pyroclastic products from the Kos-Nisyros Volcanic Complex we want to constrain the evolution of physical properties such as permeability and porosity inside a conduit. Results will then be used to enhance existing numerical models of the conduit and so help us better understand the triggering mechanisms controlling the severity of an eruption.