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Abstract:
Despite being very different in many aspects, geysers and lava fountains show similar surface expressions in the form of a two-phase (liquid and gas) jetting fountain driven by gas migration to the surface. Unlike lava fountains, some geysers are regularly active and safe to approach thus offering an opportunity to study the connection between geophysical measurements and fountain dynamics. Understanding the dynamics of geyser eruptions may therefore provide insight into the hazard assessment of their magmatic counterpart. Here we compare acoustic (infrasonic to audible spectrum), and electric (atmospheric electric field variation) data to video recordings of eruptions of Strokkur geyser in Iceland and Pōhutu geyser in the Te Puia hydrothermal area, New Zealand. While Strokkur consists of an impulsive single vent source, the Te Puia hydrothermal field consists of multiple closely spaced geysers with overlapping eruption times. We deployed a small aperture, high sample rate infrasound array to distinguish between dominant sound sources and characterize the activity of each vent. We show the comparison of parameters like fountain height, volume, duration, velocity to waveform, and spectral features of the acoustic and electric measurements of both geyser systems.Furthermore, we use the comparison of flow structures of laboratory-scale jets, jet noise scaling laws and spectral similarities to explore parameters such as jet dimensions, velocity, and turbulence regimes. This work will inform the interpretation of sound and electric charge sources from geyser and lava fountain dynamics and corresponding hazard assessment from remote observations.
