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Pyroclastic deposits of the Holocene Igwisi Hills kimberlite volcanoes, Tanzania, preserve unequivocal evidence for rapid, syn-eruptive agglutination. The unusual pyroclasts are composed of ash-sized particles agglutinated to each other by thin necks. The textures suggest the magma was disrupted into droplets during ascent. Collisions between particles occurred within a volcanic plume and on deposition within the conduit to form a weakly agglutinated, porous pyroclastic deposit. Theoretical considerations indicate that agglutination occurred over short timescales. Agglutinated clasts were entrained into weak volcanic plumes and deposited around the craters. Our results support the notion that agglutination can occur during kimberlite eruptions, and that some coherent, dense rocks in ancient kimberlite pipes interpreted as intrusive rocks could instead represent agglutinated pyroclastic rocks. Differentiating between agglutinated pyroclastic rocks and effusive or intrusive rocks in kimberlite pipes is important because of the potential effects that pyroclastic processes might have on diamond concentrations in deposits.

Peer-reviewed publications are the most common way of sharing scientific knowledge internationally. Volcanica is the only fully diamond open access journal in volcanology, publishing peer-reviewed articles without costs to authors or readers. As part of our wider journal mission, Volcanica also aims to address some of the biggest barriers in research publication and to increase accessibility to published, written research outputs. In this Editorial, we discuss Volcanica’s latest venture: to publish a complete Special Issue of Reports—one of our flagship publication formats designed specifically for cutting edge, direct observations from volcanoes—and to do so in both English and Spanish languages. Las publicaciones revisadas por pares son la forma más común de compartir el conocimiento científico a nivel internacional. Volcanica es la única revista de tipo “diamond open access” en volcanología que publica artículos revisados por pares sin ningún costo para los autores o lectores. Volcanica también tiene como objetivos reducir algunas de las mayores barreras de las publicaciones científicas y aumentar la accesibilidad a los resultados de las investigaciones publicadas. En este editorial, analizamos la última aventura de Volcanica: publicar un número especial constituido íntegramente por Reportes –uno de nuestros formatos de publicación insignia, diseñado específicamente para observaciones directas y de vanguardia sobre volcanes– en los idiomas inglés y español.

The use of Mt. Epomeo Green Tuff (MEGT) as a building stone is widespread on Ischia Island (Italy). We assess here the fire resistance of MEGT by thermally stressing samples to temperatures up to 1000 °C. Porosity and uniaxial compressive strength increase and decrease from 44% and 4.5 MPa at ambient temperature to 48% and 1.5 MPa following exposure to 1000 °C, respectively. Complementary thermogravimetric and X-ray powder diffraction analyses, experiments that monitor acoustic emissions during heating/cooling, and microstructural observations highlight that these changes are the result of thermal microcracks, formed due to the breakdown of zeolites and clays (MEGT contains 35 wt.% analcime, 15 wt.% smectite, and 3 wt.% illite) at high temperature. Although the stability of structures built from MEGT will be jeopardised at high temperature, a very low thermal diffusivity requires that fires must burn for many hours to compromise the strength of a typical dimension stone: tuffs are tough in the event of fire.