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Understanding Volcanic Eruptions Through Ash Analysis

Recent research focusing on the Cumbre Vieja volcano in the Canary Islands has uncovered significant insights into how the characteristics of magma can influence seismic activity during eruptions. The study, published in Nature Geoscience by scientists from the American Museum of Natural History and the City University of New York, illuminates the potential of volcanic ash examination as a tool for monitoring and predicting volcanic events.

According to Samantha Tramontano, a co-author of the study and a Kathryn W. Davis Postdoctoral Fellow at the Museum, while advancements have been made in forecasting the initiation of volcanic eruptions, accurately predicting the style and duration of these events remains challenging. She emphasized that if their results are applicable to other volcanic systems, real-time monitoring of magma characteristics from the surface may enhance hazard assessments significantly.

The Cumbre Vieja volcano erupted in September 2021 after a half-century of dormancy, leading to mass evacuations and significant destruction over an 85-day period. To gather vital data, Tramontano and her mentor, Marc-Antoine Longpré of CUNY, collaborated with the Instituto Volcanológico de Canarias and the Instituto Geográfico Nacional to systematically collect volcanic ash samples throughout the eruption.

These samples, covering 94 percent of the eruption duration, were transported to the Museum for thorough chemical analysis using an electron microprobe. This analysis focused on the glass content within the ash, a product of the rapidly solidified magma expelled by the volcano, resulting in a comprehensive daily dataset detailing the magma’s liquid composition, a pioneering effort in volcanic research.

One of the key findings indicated fluctuations in silica levels within the ash samples, a compound that plays a critical role in magma’s viscosity. Increased viscosity is often linked with more explosive eruptions. The research indicated that silica levels were initially high during the eruption’s onset but decreased progressively, culminating in a sudden increase two weeks prior to the eruption’s termination, likely signaling a depletion of magma from the mantle.

By correlating this chemical data with concurrent physical observations, the researchers established a connection between silica concentration and tremor intensity, which is a measurable seismic indicator of gas and liquid movement underground. The findings suggest that magma with higher silica content tends to produce stronger volcanic tremors, although further investigation is necessary to fully establish this relationship.

This study not only sheds light on the mechanisms behind volcanic tremors—an essential aspect of eruption monitoring—but also highlights the advantages of integrating petrological assessments, such as volcanic ash analysis, with geophysical data. This integrative approach aims to enhance forecasting capabilities, improve hazard management, and facilitate informed decision-making during volcanic incidents.

Longpré articulated the challenges of synchronizing fieldwork and sample processing during eruption events, which can hinder timely analysis. He stressed the importance of meticulous pre-planning and technological advancements to streamline near-site sample analysis in the future, thereby bolstering the rapid interpretation of geophysical data.

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