Volcanica最新文献

{"title":"Insight into volcanic garnet: origin and significance of garnet as exemplified by a detailed petro-mineralogical study of the Breziny andesite (Central Slovakia Volcanic Field, Western Carpathians, Central Europe)","authors":"J. Bouloton","doi":"10.30909/vol.04.02.149187","DOIUrl":"https://doi.org/10.30909/vol.04.02.149187","url":null,"abstract":"Almandine-rich garnets from a Neogene andesite of Slovakia can be divided into two main types. Garnet megacrysts are magmatic and form a chemically homogeneous group that contains, on average, about 5 wt% CaO and 4.5 wt% MgO as petrogenetically significant components. Garnets occurring in lithic fragments and garnets aggregated in garnetite lenses are characterised by Ca-poor cores (CaO <= 2 wt%) that testify for a two-step history and correspond respectively to inherited pre-anatectic and peritectic garnets. Available experimental data show that the composition of magmatic garnet megacrysts is compatible with a peritectic origin, through the fluid-absent melting of an immature metasedimentary protolith or a tonalitic gneiss. However, thermal evolution evidenced by zircons shielded in garnet rather suggests that garnet nucleated and grew by cooling of a hybrid magma pool, resulting from the complete mixing of crust- and mantle-derived melts.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43301655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Permanent, seasonal, and episodic seismic sources around Vatnajökull, Iceland, from the analysis of correlograms","authors":"Sylvain Nowé, T. Lecocq, C. Caudron, K. Jónsdóttir, F. Pattyn","doi":"10.30909/VOL.04.02.135147","DOIUrl":"https://doi.org/10.30909/VOL.04.02.135147","url":null,"abstract":"In this study, we locate and characterise the main seismic noise sources in the region of the Vatnajökull icecap (Iceland). Vatnajökull is the largest Icelandic icecap, covering several active volcanoes. The seismic context is very complex, with glacial and volcanic events occurring simultaneously and the classification between the two can become cumbersome. Using seismic interferometry on continuous seismic data (2011–2019), we calculate the propagation velocities and locate the main seismic sources by using hyperbolic geometry and a grid-search method. We identify and characterise permanent oceanic sources, seasonal glacial-related sources, and episodic volcanic sources. These results give a better understanding of the background seismic noise sources in this region and could allow the identification of seismic sources associated with potentially threatening events in real-time.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48594542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conduit system, degassing, and flow dynamics of a rhyolite lava: A case study of the Shiroyama lava on Himeshima Island, Japan","authors":"Kuniyuki Furukawa, K. Uno, Yu Horiuchi, Shintaro Murohashi, M. Tsuboi","doi":"10.30909/VOL.04.02.107134","DOIUrl":"https://doi.org/10.30909/VOL.04.02.107134","url":null,"abstract":"This study presents a description of a rhyolite lava-forming eruption, including the conduit system, degassing history during the lava flow dynamics. We examined the Pleistocene Shiroyama rhyolite lava on Himeshima Island, Japan. The lava is mainly characterized by locally developed obsidian. Based on the structural variation, the obsidian lithofacies correspond to the shallow conduit. The geological investigation and FTIR analyses showed that gas removal from the conduit magma proceeded via vesiculation, fracturing, and brecciation, allowing formation of the dense obsidian. Since the lava originally maintained some extent of water, the lava effervesced just after the effusion. This vesiculation resulted in pervasive bubble coalescence and the formation of abundant permeable pathways. The volcanic gasses escaped via those pathways, allowing collapse of the bubbles and deflation of the lava. AMS (anisotropy of magnetic susceptibility) results indicate that the lava spread concentrically.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48367886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterising vent and crater shape changes at Stromboli: implications for risk areas","authors":"M. Schmid, U. Kueppers, R. Civico, T. Ricci, J. Taddeucci, Donald Bruce Dingwell","doi":"10.30909/VOL.04.01.87105","DOIUrl":"https://doi.org/10.30909/VOL.04.01.87105","url":null,"abstract":"Active volcanoes are typically subject to frequent substantial topographic changes as well as variable eruption intensity, style and/or directionality. Gravitational instabilities and local accumulation of pyroclasts affect conditions at the active vents, through which gas-particle jets are released. In turn, the vent geometry strongly impacts the eruption characteristics. Here, we compare five high-resolution topographic data sets (<4 cm/pixel) of volcanic craters and vents from Stromboli volcano, Italy, that were acquired by unoccupied aerial vehicle (UAV) during five field campaigns between May 2019 and January 2020. This period includes two paroxysmal explosions (3 July and 28 August 2019) and exhibited significant changes on day-to-month timescales. Our results highlight changes to vent geometry and their strong control on the directionality of explosions. Recurrent UAV surveys enable the monitoring of temporal morphologic changes and aid the interpretation of observed changes in eruption style. Ultimately, this may contribute to repeatedly revised risk areas on permanently active volcanoes, especially those that are important tourist destinations.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48473918","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluating the applicability of a screen diffraction approximation to local volcano infrasound","authors":"S. Maher, R. Matoza, C. de Groot-Hedlin, Keehoon Kim, K. Gee","doi":"10.30909/VOL.04.01.6785","DOIUrl":"https://doi.org/10.30909/VOL.04.01.6785","url":null,"abstract":"Atmospheric acoustic waves from volcanoes at infrasonic frequencies (0.01–20 Hz) can be used to estimate source parameters for hazard modeling, but signals are often distorted by wavefield interactions with topography, even at local recording distances (<15 km). We present new developments toward a simple empirical approach to estimate attenuation by topographic diffraction at reduced computational cost. We investigate the applicability of a thin screen diffraction relationship developed by Maekawa [1968, doi: https://doi.org/10.1016/0003-682X(68)90020- 0]. We use a 2D axisymmetric finite-difference method to show that this relationship accurately predicts power losses for infrasound diffraction over an idealized kilometer-scale screen; thus validating the scaling to infrasonic wavelengths. However, the Maekawa relationship overestimates attenuation for realistic volcano topography (using Sakurajima Volcano as an example). The attenuating effect of diffraction may be counteracted by constructive interference of multiple reflections along concave volcano slopes. We conclude that the Maekawa relationship is insufficient as formulated for volcano infrasound, and suggest modifications that may improve the prediction capability.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":"1 1","pages":"67-85"},"PeriodicalIF":0.0,"publicationDate":"2021-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43777095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrophysical characterisation of volcanic ejecta to constrain subsurface lithological heterogeneities: implications for edifice stability at basaltic volcanoes","authors":"A. Di Muro, Fabian Schwarzlmuller, U. Kueppers, M. Heap, Donald Bruce Dingwell","doi":"10.30909/VOL.04.01.4166","DOIUrl":"https://doi.org/10.30909/VOL.04.01.4166","url":null,"abstract":"Piton de la Fournaise (PdF) is an active and dominantly e ff usive basaltic volcano. The geologic record preserves evidence of rare explosive eruptions, associated with the seaward sliding of the steep east flank and the collapse of large calderas emplacing lithic-rich breccias. Breccias of PdF o ff er the opportunity to sample a wide range of crustal lithologies. Unaltered blocks are representative of plutonic (gabbros), sub-volcanic (dolerites emplaced in sills and dykes), and volcanic (lavas) units. We document a large variability in density, porosity, P-wave velocity (dry and wet), and uniaxial compressive strength (UCS). The large variation in P-wave velocity and UCS results from the wide ranges in texture and lithology. Notably, some of the dense gabbroic units having experienced several cycles of natural reheating are comparatively weak. We infer that volcano instability should not be interpreted solely in terms of altered rock units. Rather, the large petrophysical heterogeneity of crustal rocks at PdF, and likely at many other basaltic volcanoes, must be considered when interpreting monitoring data and assessing volcano stability. Le Piton de la Fournaise (PdF) est un volcan basaltique actif et à dominante e ff usive. Les archives géologiques conservent des preuves d’éruptions explosives rares, associées au glissement vers la mer du flanc est escarpé et à l’e ff ondrement de grandes calderas produisant des brèches riches en lithiques. Les brèches de PdF o ff rent l’oppor-tunité d’échantillonner une large gamme de lithologies crustales. Les blocs non modifiés sont représentatifs des unités plutoniques (gabbros), subvolcaniques (dolérites placées dans sills et les dykes) et volcaniques (laves). Nous documentons une grande variabilité de la densité, de la porosité, de la vitesse de l’onde P (sèche et humide) et de la résistance à la compression uniaxiale (UCS). La grande variation de la vitesse de l’onde P et du UCS résulte des larges gammes de texture et de lithologie. Notamment, certaines des unités gabbroïques denses ayant subi plusieurs cycles de réchau ff ement naturel sont relativement faibles. Nous en déduisons que l’instabilité du volcan ne doit pas être interprétée uniquement en termes d’unités de roches altérées. Au contraire, la grande hétérogénéité pétrophy-sique des roches crustales à PdF, et probablement dans de nombreux autres volcans basaltiques, doit être prise en compte lors de l’interprétation des données de surveillance et de l’évaluation de la stabilité du volcan.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":"4 1","pages":"41-66"},"PeriodicalIF":0.0,"publicationDate":"2021-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44045594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fault inversion contributes to ground deformation above inflating igneous sills","authors":"J. Norcliffe, C. Magee, C. Jackson, Jonas Kopping, B. Lathrop","doi":"10.30909/VOL.04.01.0121","DOIUrl":"https://doi.org/10.30909/VOL.04.01.0121","url":null,"abstract":"Magma emplacement is commonly accommodated by uplift of the overburden and free surface. By assuming this deformation is purely elastic, we can invert the shape and kinematics of ground deformation to model the geometry and dynamics of underlying intrusions. However, magma emplacement can be accommodated by viscoelastic and/or inelastic processes. We use 3D seismic reflection data to reconstruct how elastic bending and inelastic processes accommodated emplacement of a Late Jurassic sill offshore NW Australia. We restore syn-emplacement ground deformation and compare its relief to sill thickness, showing that: (i) where they are equal, elastic bending accommodated intrusion; but (ii) where sill thickness is greater, inversion of a pre-existing fault and overburden compaction contributed to magma accommodation. Our results support work showing inelastic processes can suppress ground deformation, and demonstrate magmatism can modify fault displacements. Reflection seismology is thus powerful tool for unravelling links between magma emplacement, ground deformation, and faulting.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45290625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental constraints on volcanic ash generation and clast morphometrics in pyroclastic density currents and granular flows","authors":"A. Hornby, U. Kueppers, Benedikt Mauer, Carina Poetsch, Donald Bruce Dingwell","doi":"10.30909/vol.03.02.263283","DOIUrl":"https://doi.org/10.30909/vol.03.02.263283","url":null,"abstract":"<p>Pyroclastic density currents (PDCs) present perhaps the greatest proximal primary hazard of volcanic activity and produce abundant fine ash that can present a range of health, environment and infrastructure hazards. However, direct, fully quantitative observation of ash production in PDCs is lacking, and little direct evidence exists to constrain the parameters controlling ash generation in PDCs. Here, we use an experimental approach to investigate the effects of starting mass, material density and ash removal on the efficiency of ash generation and concurrent clast rounding in the dense basal flow of PDCs. We employ a rotary drum to tumble pumice and scoria lapilli clasts over multiple transport &#8220;distance&#8221; steps (from 0.2 to 6&#160;km). We observe increased ash generation rates with the periodic removal of ash during the experiments and with increasing starting mass. By scaling to the bed height and clast diameter we obtain a general description for ash production in all experiments as a function of flow distance, bed height and average clast diameter. We confirm that changes in lapilli shape factors correlate with the ash fraction generated and that the grain size of ash produced decreases with distance. Finally, we estimate shear rate in our experiments and calculate the inertial number, which describes the ratio between clast-scale and flow-scale rearrangement during flow. We show that, under certain conditions, fractional ash production can be calculated accurately for any starting mass solely as a function of the inertial number and the flow distance. This work sheds light on some of the first systematic and generalizable experimental parameterizations of ash production and associated clast evolution in PDCs and should advance our ability to understand flow mobility and associated hazards.</p>","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43739456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Segment tip geometry of sheet intrusions, II: Field observations of tip geometries and a model for evolving emplacement mechanisms","authors":"T. Stephens, R. Walker, D. Healy, A. Bubeck","doi":"10.31223/x5sw28","DOIUrl":"https://doi.org/10.31223/x5sw28","url":null,"abstract":"Igneous sheet intrusions are segmented across several orders of magnitude, with segment tip geometry commonly considered indicative of the propagation mechanism (brittle or non-brittle). Proposed propagation mechanisms are inferred to represent host rock mechanical properties during initial magma emplacement; typically, these models do not account for segment sets that show a range of tip geometries within the same lithology. We present a detailed structural characterization of basaltic sill segments and their associated host rock deformation from the Little Minch Sill Complex, Isle of Skye, UK, and a broader comparison with segment geometries in three additional intrusive suites (Utah, USA; and Mull and Orkney, UK).  Each separate host lithology shows multiple tip geometries and styles of host rock deformation, from elastic-brittle fracture, to viscous indentation and fluidisation. We attribute this range of host rock deformations to evolving conditions that occur at the tips both during sheet growth and arrest.  ","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45415021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling source parameters of quasi-periodic tremor","authors":"J. Traphagan, J. Lees","doi":"10.30909/vol.03.02.251262","DOIUrl":"https://doi.org/10.30909/vol.03.02.251262","url":null,"abstract":"Modeling harmonic tremor recorded at volcanoes is an essential practice in improving eruption forecasting methods and warning systems. We model the conduit dynamics of quasi-periodic tremor (chugging) recorded at Karymsky, Tungurahua, and Fuego volcanoes to estimate its source characteristics. Chugging mechanisms are estimated using two theoretical models originally derived in Garcés [1997, doi: https://doi.org/10.1029/1999JB900096] and Girona et al. [2019, doi: https://doi.org/10.1029/2019JB017482], respectively. Comparisons of the conduit and fluid output parameters suggests that chugging is primarily limited to near-surface oscillations and outgassing due to an accumulation of gas between eruptive episodes. The modeled results indicate clustered release of volatiles exsolved from a deeper magma conduit region, triggered by an initial explosion. This interpretation is consistent with both infrasonic and seismic observations at each volcano.","PeriodicalId":33053,"journal":{"name":"Volcanica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47660246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}