Scientists accurately size ancient Greek volcanic eruption to better assess risk of future eruptions

Volcanic eruptions are both awe-inspiring and perilous. They can be so colossal that their effects may be felt worldwide, causing a global drop in temperature. To gauge the magnitude of volcanic eruptions, experts estimate both the volume of magma and the deposition volume, but this can be challenging as these values are often difficult to determine accurately. Additionally, deposits from violent historical eruptions may be partially or completely underwater, complicating geological investigations and hindering accurate sizing of past eruptions.

However, an international team of scientists, led by marine geoscientist Dr. Jens Karstens of GEOMAR Helmholtz Center for Ocean Research Kiel, has utilized the latest geological and geophysical techniques to reassess the Minoan eruption that occurred 3,600 years ago on the Greek island of Santorini. Their research, which has been published in the journal Nature Communications, provides one of the most precise volume estimates of any large volcanic eruption, establishing a model for measuring and classifying volcanic eruptions globally. This breakthrough allows for improved hazard assessments and more accurate determinations of magma volumes.

Dr. Karstens emphasizes the need to understand the risks of volcanic eruptions, stating that while climate change risks can be evaluated using models and earthquake risks are relatively well-understood, our knowledge of volcanic risks is limited. He emphasizes the importance of knowing how often eruptions of a specific size occur in order to accurately assess the danger. By conducting a thorough investigation of the Minoan eruption, the team has made a significant contribution to this area of study.

Excavation site of the city of Akrotiri on Santorini, buried by the Minoan eruption. Credit: Jonas Preine

The Minoan civilization was Europe’s earliest advanced society. Approximately 3,600 years ago, the Minoan eruption occurred during the Holocene epoch, completely burying the city that is now the archaeological site of Akrotiri. Previous calculations estimated that the eruption was one of the largest in the past 10,000 years, with an ejected magma volume of up to 86 cubic kilometers. However, new analysis by the scientific team indicates that the eruption was much smaller, ranging from 26 to 41 cubic kilometers, or only one-third to one-half the previous estimate.

To estimate the magnitude of the volcanic eruption, the researchers employed various methods from multiple research cruises. During a research cruise called POS513 aboard the research vessel POSEIDON in 2017, they detected ash deposits from the Minoan eruption in 41 sediment cores, allowing them to determine the ash volume. They used computed tomography to ascertain the density of the sediment cores, which enabled them to determine the ejected magma’s actual pure volume. Furthermore, using seismic reflection data from another research cruise (POS538), they identified and characterized the deposition of pyroclastic flows around the island and the caldera’s center.

By combining this data, the scientists calculated precise values for all of the eruption’s individual components for the first time. Previously, estimates of the eruption volume were based on either caldera collapse volume or incomplete eruption product estimates, which had limited explanatory power.

Dr. Karstens underscores that volcanic eruptions can cause fatalities and affect the environment. Therefore, the team’s findings will help us comprehend explosive volcanic eruptions and their magnitudes better, resulting in improved risk assessments.

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