Explosive eruptions of Kolumbo Central Volcano and associated tephra fallout hazards assessment

Abstract We present a study of potential tephra fallout hazards from explosive eruptions at the submarine Kolumbo Central Volcano, located in the Aegean Sea, Greece. Using expert elicitation and numerical simulations of plume dynamics coupled with tephra dispersal and deposition, we map the likely tephra deposit from the 1650 CE paroxysm (likely a Plinian-scale eruption and the only documented event from this volcano) and develop probabilistic tephra fallout hazard maps and curves for potential Plinian-style future eruptions expected within the next 30 years. The numerical results of the likely deposit produced by the 1650 CE eruption indicate predominant eastward dispersal of material, with tephra fallout (exceeding 10 kg/m² with a probability greater than 50%) possibly affecting the islands up to about 100 km east of Kolumbo Central Volcano. Modest fallout of 1 kg/m 2 likely reached as far northeast as Turkey (250 km to the volcano location), consistent with historical accounts. Tephra deposition on Santorini island (located upwind) is attributed to the upwind spread of the umbrella cloud. Similar dispersal patterns are expected for future Plinian scale eruptions within the next 30 years. The 50% exceedance footprint for a 10 kg / m 2 load spans several thousand km 2 . However, for a 5% probability of this tephra load, the footprint area could be tens of thousands of km 2 . Seasonal variations are minimal, though summer scenarios suggest greater northward dispersal. The probability of tephra loads above 10 kg/m 2 reaching mainland Greece remains below 10%. Regional impacts of tephra fall include disruption of transport, threats to infrastructure, health risks, and economic losses in tourism and agriculture. These results underscore the importance of assessing volcanic hazards at poorly known volcanoes in tourist areas, where even a single eruption can have widespread consequences.