First experimental observations on melting and chemical modification of volcanic ash during lightning interaction

Experimental generation of fulgurite under realistic lightning discharge conditions

Fulgurites have been documented in geological deposits from throughout Earth's history. They have also been assigned a potential role in prebiotic chemistry as a source of reactants. Fulgurites are generated in nature by cloud-to-ground lightning strikes. The unpredictability in space and time of the occurrence of lightning events has limited the investigation of both the mechanisms by, and the conditions under, which fulgurites form. A laboratory-based approach can mitigate these limitations. Here, we describe experimentally generated fulgurites generated from Laacher See volcanic ash. We employ a DC source with a trigger-pulse setup in a high voltage laboratory, whose capabilities enable experimental conditions that correspond closely to the electrical characteristics of natural lightning strikes. The experimentally generated fulgurites closely resemble naturally-occurring fulgurites in both state and texture. These experimental investigations yield a high reproducibility of the characteristic of fulgurites generated under well-constrained conditions, enabling some inferences to be made regarding the processes involved in the generation of fulgurites in nature. This work provides a basis for a systematic characterization of experimental fulgurites and the characteristic of lightning discharges.

Localized microwave-heating (LMH) of basalt - Lava, dusty-plasma, and ball-lightning ejection by a "miniature volcano"

This paper presents various phenomena obtained by localized microwave-heating (LMH) of basalt, including effects of inner core melting, lava eruption and flow (from the molten core outside), plasma ejection from basalt (in forms of fire-column and ball-lightning), and effusion of dust (deposited as powder by the plasma). The experiments are conducted by irradiating a basalt stone (~30-cm³ volume, either naturally shaped or cut to a cubic brick) in a microwave cavity, fed by an adaptively-matched magnetron (~1 kW at 2.45 GHz). Effects of LMH and thermal-runaway instability in basalt are observed and compared to theory. Various in- and ex-situ diagnostics are used in order to characterize the dusty-plasma observed and its nanoparticle products. The resemblance of the experimental phenomena obtained in small laboratory scale to gigantic volcanic phenomena in nature is noticed, and its potential relevance to further volcanic studies is discussed. In particular, we show that LMH could be instrumental for laboratory demonstrations and simulations of miniature-volcano effects, such as lava flows, formation of volcanic glass (obsidian), eruption of dusty-plasma and volcanic ash, and ejection of ball lightning. These findings might be significant as well for various applications, such as drilling and mining, microwave-induced breakdown spectroscopy (MIBS), mineral extraction, and powder production directly from basalts.