PYTON: analysing PYroclast Textures to understand vOlcaNic behaviour

• Applicant: Dr. Ulrich Küppers
• Subject Area: Geology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541925548

Explosive volcanic eruptions are a major global hazard as their location, onset, duration, and intensity cannot be influenced. Their impact can be far-reaching and catastrophic, and they have been responsible for tens of thousands of fatalities in the last centuries. As approx. 15% of the global population today lives near volcanoes that are likely to erupt again, it is essential that we work towards enhancing the related hazard assessment. We aim to contribute to advancing volcanology from a largely observing to a forecasting discipline by quantitatively understanding eruption and transport processes. During explosive eruptions, magma is fragmented, ejected into the atmosphere, and eventually deposited following different transport processes. As most of this cannot be directly observed (happening inside the conduit or due to the involved danger), we propose to derive eruption, transport, and sedimentation characteristics through a close investigation of pyroclasts who witnessed these processes. Sub-Plinian to Plinian eruptions of felsic to intermediate magma composition are the ones with the most likely damaging impact on human life; therefore, we have selected four volcanoes to study the deposits of key eruptions: Laacher See (Germany), Montagne Pelée (France), Sete Cidades (Portugal) and Vesuvius (Italy). The main questions are: What controls variations in eruptive behaviour (style, intensity, duration)? What affects (intrinsically) the mobility of PDCs? Our goal is to expand the petrophysical and morphological characterization of pyroclasts, measuring porosity and shape parameters of porous pyroclasts. Porosity reflects the interplay of volatile content, magma ascent conditions, and degassing and controls the final overpressure. Brittle fragmentation of felsic magma generates angular pyroclasts. As they are not mechanically strong, secondary processes after fragmentation may alter their shape. Morphology analysis will allow for defining shape families that may point to (or exclude the influence of) certain transport mechanisms. We have organised collaborative field campaigns, involving MSc students from LMU and partner institutions to produce statistically representative data sets of the petrophysical properties of pyroclasts (volume, weight, humidity, porosity) of the target volcanoes in WPs 1 - 3. This will reduce logistics but more importantly avoid post-sampling clast shape changes. A representative subset of samples will be further analysed at LMU for the efficiency of rounding following abrasion and comminution in tumbling experiments (WP 4, 5). The generated data will shed light on the dynamical evolution of eruption processes as well as complex interplay of several transport processes, responsible for the final deposits (WP 6). These characteristics are complementary to routine description of pyroclastic deposits (grain size, thickness, dispersal) and an important contribution to enhanced hazard mitigation of explosive eruptions.

• DFG Programme: Research Grants