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Kimberly Genareau

Publications and source records attributed to Kimberly Genareau.

3 recordsLinked to original sources

Volcanic electrification: Recent advances and future perspectives

The electrification of volcanic plumes has been described intermittently since at least the time of Pliny the Younger and the 79 AD eruption of Vesuvius. Although sometimes disregarded in the past as secondary effects, recent work suggests that the electrical properties of volcanic plumes reveal intrinsic and otherwise inaccessible parameters of explosive eruptions. An increasing number of volcanic lightning studies across the last decade have shown that electrification is ubiquitous in volcanic plumes. Technological advances in engineering and numerical modelling, paired with close observation of recent eruptions and dedicated laboratory studies (shock-tube and current impulse experiments), show that charge generation and electrical activity are related to the physical, chemical, and dynamic processes underpinning the eruption itself. Refining our understanding of volcanic plume electrification will continue advancing the fundamental understanding of eruptive processes to improve volcano monitoring. Realizing this goal, however, requires an interdisciplinary approach at the intersection of volcanology, atmospheric science, atmospheric electricity, and engineering. Our paper summarizes the rapid and steady progress achieved in recent volcanic lightning research and provides a vision for future developments in this growing field.

Bulletin of Volcanology

Influence of grain size and shape on volcanic ash electrical conductivity

Few studies have examined the electrical properties of volcanic ash or considered the effects of physical characteristics, such as grain size and shape on its electrification. This study measures the resistivity of eight volcanic ash samples, three milled-samples and five natural ashfall samples from Alaska, U.S.A., using a current amplifier and examines the influence of particle size and particle shape on calculated grain conductivity. Grain conductivities are calculated by applying spherical, oblate, and prolate ellipsoidal shape parameters within a general effective media equation. Volcanic ash is an electrically insulating material with average resistivity values ranging from 1.732E 7 to 1.606E 12 Ωm. Results show that grain size has a limited impact on resistivity. Calculated grain conductivities remained within the same order of magnitude between the three different shape calculations ranging between 1.367E − 7 and 2.196E − 12 S/m using the spherical shape parameter. Electrical measurements of heterogeneous powders are complex and challenging. This study aims to expand the community's dataset and understanding of the electrical properties of volcanic ash and the impact of different physical characteristics. This has implication for understanding ash hazards to electrical infrastructure and volcanic lightning.

Journal of Volcanology and Geothermal Research

Lightning effects on the grain size distribution of volcanic ash

Natural volcanic ashfall samples were examined, and high-current (~100 kA) electrical impulse experiments were conducted to reveal the changes in grain size that can occur during lightning discharge. Experiments on pseudo ash samples manufactured from volcanic deposits of both rhyolitic and basaltic composition show that aggregates of very fine grained ash particles (<32 μm) melt and degas to form vesiculated pumice fragments >100 μm in size. In some cases, bubbles <5 μm in diameter expand and detach from the outer surface of the pumice to form hollow spheres of glass, one type of lightning-induced volcanic spherule, while other bubbles fragment. Volcanic ashfall from the 2009 Redoubt eruption and the 2016 Pavlof eruption contains both pumiceous grains and individual spherules. Results of this study reveal that volcanic lightning will alter the grain size distribution of ash through melting, vesiculation, and fragmentation of individual particles or ash aggregates.

Geophysical Research Letters