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Estimating Effusive Eruption Volumes to Reconstruct the Volcanic History of Methana, Greece

Moritz Lang , Nicole Richter, Klaus Reicherter

Abstract

Estimating eruption volumes of dormant volcanoes is necessary to understand the activity of volcanic systems in the past and potentially forecast their behavior in the future. Methana Volcano, as part of the South Aegean Volcanic Arc (Greece), consists of at least twenty-two andesitic to dacitic effusive eruptions during the last approximately 2.1 Ma. The last eruption took place in historical times around 230 BCE and produced a ~ 2.5 km-long lava flow. We present a study of effusive eruption volume estimations using the open-source Copernicus DEM GLO-30 in combination with bathymetry data to include the offshore extent of coastal lava flows. Bulk volumes of the effusive phases are converted into their respective dense rock equivalents (DRE) by removing the porosity and voids induced by brecciation, fracturing and degassing during an eruption. The calculated DRE volumes range between 0.1 Mm³ and ~170 Mm³ per eruption, with the largest being the afore mentioned historical eruption. The combined DRE volumes for each evolutionary phase indicate a variable activity of Methana Volcano over time with relatively moderate effusive volumes between 0.6-2.1 Ma, lower volumes between 0.4-0.6 Ma and higher volumes for the phases starting around 0.4 Ma and thereafter. The temporal changes in effusive eruption volumes coincide with the activation of different fault patterns in the wider area of Methana Volcano. However, further investigations, including precise dating of Methana´s volcanic products, are crucial to better constrain the volcanic activity within the single evolutionary phases over time and their link to regional tectonics.