THE VULKAN IN WAAKIRCHEN: VOLCANO MONITORING MEETS EXPERIMENTAL VOLCANOLOGY

Volcanic eruptions are an inevitable natural threat. The range of eruptive styles is large and short term fluctuations of explosivity or vent position pose a large risk that is not necessarily confined to the immediate vicinity of a volcano. Explosive eruptions rather may also affect aviation, infrastructure and climate, regionally as well as globally. Multi-parameter monitoring networks are deployed on many active volcanoes to record signs of magmatic processes and help elucidate the secrets of volcanic phenomena.

However, our mechanistic understanding of many processes hiding in recorded signals is still poor. As a direct consequence, a solid interpretation of the state of a volcano is still a challenge. In an attempt to bridge this gap, we combined volcanic monitoring and experimental volcanology. We performed field-based experiments and recorded them with a variety of scientific instruments, namely 1) Doppler Radar (DR), 2) high-speed and high-definition cameras, 3) acoustic and infrasound sensors, 4) pressure transducers, and 5) electrically conducting wires. The experiments were performed at controlled sample porosity (25 to 75 vol.%) and size (60 mm height and 25 mm and 60 mm diameter, respectively), confinement geometry, and applied pressure (4 to 18 MPa) and temperature (25 and 850 °C). During the experiments, we fragmented cylindrical samples of several volcanoes, drilled from natural volcanic rock samples.

We present how the velocity of the ejected pyroclasts was measured by and evaluated for the different approaches and how it was affected by the experimental conditions and sample characteristics. We show that all deployed instruments successfully measured the pyroclast ejection, giving coherent results of up to 130 m/s. This is a very encouraging result and of paramount importance as it proofs the applicability of these independent methods to volcano monitoring. Each method by itself may enhance our understanding of the pressurisation state of a volcano, an essential factor in ballistic hazard evaluation and eruption energy estimation.