Newswise — Spectacular, violent, and perilous are volcanic eruptions. Even global impacts can arise from huge explosive eruptions. To rank the size of volcanic eruptions, magma volume and deposition volume are calculated. Volcanologists gauge these metrics to compare eruption sizes or gauge explosiveness. However, precise measurement is often unfeasible, making it challenging to determine magma volume and eruption extent. Notably, geological investigations are difficult due to the fact that deposits from the most violent historical eruptions are partly or entirely submerged, hindering accurate measurement. Consequently, assessing the risk reliably and sizing past eruptions precisely has been challenging.

Dr. Jens Karstens of GEOMAR Helmholtz Centre for Ocean Research Kiel has spearheaded an international team of researchers who have utilized advanced geological and geophysical techniques to remap the Minoan eruption of Santorini, Greece, which occurred 3,600 years ago. Their findings, which have been published in the journal Nature Communications, represent one of the most precise estimations of volume for a large volcanic eruption to date. Additionally, their research presents a methodology that can be used to classify and measure other volcanic eruptions around the world with greater accuracy. This study will help in assessing the risks posed by such events and serves as a benchmark for more accurately determining magma volumes.

Dr. Karstens, the lead author of the study, confirms that volcanic eruptions can have global effects, such as a decrease in global temperatures. He notes that while we can model climate change risks and have a decent understanding of earthquake risks, we lack sufficient knowledge when it comes to volcanoes. There is a "blind spot" in our understanding of volcanic eruptions, and it is crucial that we learn to assess their consequences more accurately. To better evaluate the risks, it is necessary to determine the frequency of eruptions of a certain magnitude. Precise volume calculations are crucial for this purpose. The study of the Minoan eruption has made an important contribution in this regard.

The Minoans were the first advanced civilization in Europe, and their city, Akrotiri, was buried by the volcanic eruption that occurred approximately 3,600 years ago during the Holocene epoch. Previous estimates had suggested that the eruption was enormous, with 86 cubic kilometers of ejected magma, making it one of the largest eruptions in the past 10,000 years. However, the recent analysis by the scientific team indicates a significantly smaller scale, with the event estimated to be only one-third to one-half as large, or 26-41 cubic kilometers of magma ejected at the time.

To calculate the magnitude of the volcanic eruption, the research team utilized various methods from multiple research cruises. They detected ash deposits from the Minoan eruption in 41 sediment cores collected during the research cruise POS513 aboard the research vessel POSEIDON in 2017. This allowed them to determine the ash volume of the eruption. Since ejected magma solidifies into materials with varying porosities, the team used computed tomography-based techniques to determine the density of the sediment cores and thus the actual volume of pure magma ejected. Additionally, they utilized seismic reflection data from research cruise POS538 to identify and characterize the deposition of pyroclastic flows, which are hot gases, ash, and debris ejected by the volcanic eruption, around the island. These data also enabled them to characterize material that fell into the center of the caldera, which is the crater at the volcano's center.-

By combining the data they collected, the scientific team was able to draw conclusions about the scale of the Minoan eruption. This study marks the first time that such precise values have been calculated for all individual components. Previous estimates of the eruption volume were based solely on either the volume of the caldera collapse or incomplete estimates of the eruption products, both of which were limited in their explanatory power.

Dr. Karstens emphasizes the importance of understanding explosive volcanic eruptions and their magnitudes, as they can result in the loss of human lives and have significant impacts on the climate. He further highlights that the results obtained by their study add another piece to the puzzle of this understanding, and that this can lead to improved risk assessments for future volcanic events.

Journal Link: Nature Communications