Volcanica https://www.jvolcanica.org/ojs/index.php/volcanica <p><em>Volcanica</em>&nbsp;seeks to publish high-quality, rigorously peer reviewed research pertaining to volcanology and related disciplines, while eliminating submission fees and keeping content freely accessible.</p> en-US <p>Submission of an original manuscript to <em>Volcanica&nbsp;</em>will be taken to mean that it represents original work <strong>not previously published</strong>, and <strong>not being considered for publication elsewhere</strong>.&nbsp;</p> jifarq89@googlemail.com (Jamie Farquharson) farquharson@jvolcanica.org (Jamie Farquharson) Wed, 07 Mar 2018 17:34:17 +0000 OJS http://blogs.law.harvard.edu/tech/rss 60 Unravelling intrusion-induced forced fold kinematics and ground deformation using 3D seismic reflection data https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/2 <p>Sills emplaced at shallow-levels are commonly accommodated by overburden uplift, producing forced folds. We examine ancient forced folds developed above saucer-shaped sills using 3D seismic reflection data from the Canterbury Basin, offshore SE New Zealand. Seismic-stratigraphic relationships indicate sill emplacement occurred incrementally over ~31 Myr between the Oligocene (~35–32 Ma) and Early Pliocene (~5–4 Ma). Two folds display flat-topped geometries and amplitudes that decrease upwards, conforming to expected models of forced fold growth. Conversely, two folds display amplitudes that locally increase upwards, coincident with a transition from flat-topped to dome-shaped morphologies and an across-fold thickening of strata. We suggest these discrepancies between observed and expected forced fold geometry reflect uplift and subsidence cycles driven by sill inflation and deflation. Unravelling these forced fold kinematic histories shows complex intrusion geometries can produce relatively simple ground deformation patterns, with magma transgression corresponds to localisation of uplift.</p> Jennifer Reeves, Craig Magee, Christopher Aiden-Lee Jackson ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/2 Wed, 07 Mar 2018 17:34:42 +0000 Unrest at the Nevados de Chillán volcanic complex: a failed or yet to unfold magmatic eruption? https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/7 <p>Resuming erupting activity at volcanoes that have been long quiescent poses a significant challenge to hazard assessment, as it require assessment of whether the change in activity is an isolated event or the beginning of a new eruptive sequence. Such inception is often poorly characterised as quiescent volcanoes tend to be poorly equipped and not extensively monitored, especially with respect to gas geochemistry. Here, we report gas composition and flux measurements from a newly opened vent at the very onset of eruptive activity at the Nevados de Chillán volcanic complex (Chile) in January-February 2016. The molar proportions of H<sub>2</sub>O, CO<sub>2</sub>, SO<sub>2</sub>, H<sub>2</sub>S and H<sub>2</sub> gases are found to be 98.4, 0.97, 0.11, 0.01 and 0.5 mol% respectively. The mean SO<sub>2</sub> flux recorded in early February 2016 during periods of eruptive discharge amounts to 0.4-0.6 kg s<sup>-1</sup>. Our results indicate that the new vent opening was propelled by magmatic gases, triggering repeated eruptions. Ash particles ejected by the first blast of 8 January are dominated by lithic fragments of dacitic composition. By contrast the ash ejected in a subsequent eruption contains both lithic fragments of dense dacite, and a fresher, sparsely vesicular material of basaltic andesite composition. By October 2017 the ejected ash is back to being dominated by the dense dacitic lithic material. Together with the seismic and deformation record, these observations point to the explosive activity resulting from a small intrusion of basaltic to andesitic magma at shallow level. The fate of this magma, whether stalling or eventually triggering a magmatic eruption, remains to be seen, but current observations suggest the former is most likely.</p> Yves Moussallam, Philipson Bani, C. Ian Schipper, Carlos Cardona, Luis Franco, Talfan Barnie, Álvaro Amigo, Aaron Curtis, Nial Peters, Alessandro Aiuppa, Gaetano Giudice, Clive Oppenheimer ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/7 Mon, 07 May 2018 20:35:59 +0000 Fire resistance of the Mt. Epomeo Green Tuff, a widely-used building stone on Ischia Island (Italy) https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/6 <p>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.</p> Michael Heap, Alexandra Kushnir, Luke Griffiths, Fabian Wadsworth, Gian Marco Marmoni, Matteo Fiorucci, Salvatore Martino, Patrick Baud, H. Albert Gilg, Thierry Reuschlé ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/6 Mon, 07 May 2018 00:00:00 +0000 Rapid hazard assessment of volcanic ballistic projectiles using long-exposure photographs: insights from the 2010 eruptions at Tungurahua volcano, Ecuador https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/5 <p>Assessing hazard associated to volcanic ballistic projectiles is essential to limit fatal incidents close to erupting vents. Current state-of-the-art methods using high-speed visual and thermal images and volcanic radars permit to obtain high resolution information during explosive events but are limited to few laboratory volcanoes. Nowadays, long-exposure photographs at erupting volcanoes have become common and can be used to obtain meaningful information. In this paper I present a method to extract volcano-physical data from the projectile parabolic trajectory after adequate scaling and projection. The results, obtained from the analysis of 28 photographs from three eruptive phase at Tungurahua volcano in 2010, allowed to constrain the geometry of the vent (20 m-diameter for the upper conduit and 70 m-diameter inner crater), the diameter of the ballistic projectiles (up to 4.3 m), their launching angle (50 to 90°), their minimum launching velocity (40 to 145 m.s<sup>-1</sup>), and their maximum distance reach (up to 1330 m from the vent). This turnkey method can help to characterize eruptive dynamics as well as to perform rapid hazard assessment at dangerously explosive erupting volcanoes.</p> Benjamin Bernard ##submission.copyrightStatement## http://creativecommons.org/licenses/by/4.0 https://www.jvolcanica.org/ojs/index.php/volcanica/article/view/5 Mon, 04 Jun 2018 08:13:44 +0000