1,720,996 research outputs found
Unusual volcanic instability and sector collapse configuration at Chimpa volcano, central Andes
No full textUpper Miocene Chimpa volcano is one of the largest stratovolcanoes of the back–arc region of the central Andes. The gentle–sloped volcano underwent previously unrecognized volcanic instability, consisting of ≈ 2 km3 mass– wasting processes and catastrophic sector collapse, whose characteristics have been identified by means of stratigraphy, geological mapping and structural analysis. The origin of instability at Chimpa can be attributed to tectonic faulting, hydrothermal alteration and overloading. These common promoting and triggering factors have produced an unusual configuration of the volcano gravitational instability, characterized by parallel landslide scars delimiting unstable sectors on eastern and western volcano flanks, with large toreva blocks sliding in opposite directions, perpendicular to the flow direction of a subsequent long–run out debris avalanche. Even if the style of such a complex volcanic instability has never been described before, its identification may be also useful to study volcano sector failures and mass–wasting deposits in other volcanoes worldwide.Fil: Norini, Gianluca. Consiglio Nazionale delle Ricerche; Italia. Istituto di Geologia Ambientale e Geoingegneria; ItaliaFil: Bustos, Emilce. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Arnosio, José Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Baez, Walter Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Zuluaga, María Clara. Servicio Geologico Colombiano.; ColombiaFil: Roverato, Matteo. Yachay Tech University; Ecuado
MECANISMOS DE EMPLAZAMIENTO Y DESTRUCCIÓN DE LOS DOMOS LÁVICOS ASOCIADOS A LA CALDERA DEL CERRO BLANCO, PUNA AUSTRAL
No full textUsing digital elevation models for morphological analysis of La Hoyada Volcanic Complex
Full text linkLas formas volcánicas resultan del balance de procesos constructivos y destructivos que afectan a los edificios volcánicos, por lo tanto el estudio de los rasgos volcánicos contribuye al entendimiento de la evolución del volcanismo de una zona. El Complejo Volcánico La Hoyada (Mioceno superior-Plioceno) se encuentra en el flanco oriental de la cordillera de San Buenaventura, en la provincia de Catamarca, Argentina. Esta contribución presenta una aplicación de modelos de elevación digital para el análisis morfológico del Complejo Volcánico La Hoyada, con el objetivo de identificar y evaluar las formas volcánicas de la región, para entender la evolución de este complejo volcánico antiguo con respecto a las manifestaciones volcánicas de la zona. El análisis morfológico se realizó usando los modelos de elevación digital ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) y SRTM (Shuttle Radar Topographic Mission), además de la evaluación de imágenes SPOT. Se realizaron distintos productos derivados de los modelos de elevación digital para llevar a cabo la identificación de morfologías areales. A través del análisis de los datos se identificaron 6 dominios morfológicos, cada uno representa un volcán individual de este Complejo. La actividad tectónica de la Puna Austral y el volcanismo moderno de la zona son los factores responsables de la destrucción de estos edificios volcánicos. Los rasgos volcánicos están mejor preservados hacia el norte del complejo, por lo tanto el grado de conservación podría indicar una migración de la evolución del volcanismo de sur a norte. Esta metodología constituye una herramienta fundamental para comprender la evolución volcánica de complejos volcánicos erodados de larga duración.Volcanoes´ shapes result from constructional and destructional events; consequently, the study of volcanic features gives insight into the volcanic evolution. La Hoyada Volcanic Complex (Upper Miocene- Pliocene) is located in the eastern flank of San Buenaventura ridge, in Catamarca, Argentina. This study shows an application of digital elevation models for the volcanic area La Hoyada. The aim of this study is to examine the volcanic landforms because volcanic feature understanding of La Hoyada Volcanic Complex is an important tool for unravelling the evolution of this ancient and eroded volcanic complex. Morphological analysis of La Hoyada was performed using ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) and SRTM (Shuttle Radar Topographic Mission) Digital Elevation Models. The morphological evaluation was complemented by using high resolution images SPOT. Several products were derived from both Digital Elevation Models to identify areal morphologies. Through the evaluation of Digital Elevation Models derived data, as much as 6 morphological domains can be recognized each one representing a single volcano.Tectonic activity and modern volcanism in this area are responsible for the destruction of the volcanic edifices of La Hoyada. The partially conserved volcanic features are more distinguishable towards the north; hence, the grade of preservation could indicate that the evolution of this volcanic center was from south to north. This methodology provides a powerful tool for understanding the volcanic evolution of eroded long-lived volcanic complexes.Fil: Bustos, Emilce. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energia No Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energia No Convencional; ArgentinaFil: Arnosio, José Marcelo. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energia No Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energia No Convencional; ArgentinaFil: Norini, Gianluca. Consiglio Nazionale delle Ricerche; Itali
Volcanic debris avalanche transport and emplacement at Chimpa volcano (Central Puna, Argentina): Insights from morphology, grain-size and clast surficial textures
No full textUnderstanding the flow dynamics in debris avalanches is an important tool to advance the knowledge about lateral failures of volcanoes, a fundamental step towards an accurate risk assessment and mitigation in volcanic areas. We describe the morphological, grain-size, and clast surficial textures of the Casana volcanic debris avalanche deposit emplaced by the sector collapse of Chimpa volcano (Central Puna, Argentina). We focused our analysis on the volcanic debris avalanche deposit, characterized by ridges, reduction in downflow matrix grainsize, jigsaw-cracked blocks in the whole extent of the deposit, collision superficial textures in grains (fractures, percussion marks, and voids). Sedimentological and textural analysis show a progressive disintegration and fracturing of the larger particles with greater distance in a dry, granular flow with minimal internal deformation during propagation. Casana avalanche behaved like a rigid body in the proximal area and as a granular flow in the medial and distal reach. Block sliding mechanisms generated the toreva block in the proximal region whereas granular flow produced the debris avalanche deposits. This is an example of how different mechanisms can interact during debris avalanche emplacement, which are strictly related to the cause of the volcano instability, the lithology and the degree of alteration of the source mass, and its interaction with paleotopography. Although the geological risk of the proposed study area is low, the study of Casana VDAD is important to understand similar processes in other volcanoes providing constraints to hazard assessment.Fil: Bustos, Emilce. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Capra, Lucía. Universidad Nacional Autónoma de México. Centro de Geociencias, Campus Juriquilla, Querétaro; MéxicoFil: Arnosio, José Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Norini, Gianluca. Consiglio Nazionale delle Ricerche; Itali
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Estratigrafía y evolución del Complejo Volcánico Cerro Blanco, Puna Austral, Argentina
Full text linkCerro Blanco Volcanic Complex is located in Catamarca Province in the southern limit of Andean plateau. It corresponds to a system of nested calderas, with associated domes and pyroclastic deposits. All erupted products are rhyolitic/rhyodacitic in composition and constitute the youngest (Middle Pleistocene-Holocene) collapse calderas system in the Southern Central Andes based on the available radiometric ages. The Cerro Blanco Volcanic Complex hosts an active, small geothermal field and is subsiding with an average velocity of 0.87 cm/year. Despite the existence of numerous studies on regional volcanism of the southern edge of the Andean plateau, the stratigraphy of most of eruptive centers in the region is poorly understood. This study presents a new stratigraphic scheme for the Cerro Blanco Volcanic Complex using a combination of lithostratigraphic units and Unconformity Bounded Stratigraphic Units, plus the application of volcanic activity units and lithosome concept. The results allowed to reconstruct the Cerro Blanco Volcanic Complex evolution in three main eruptive epochs that constitute an eruptive period: i) the Cortaderas eruptive epoch (Middle Pleistocene) is represented by the homonymous synthem and characterized by explosive boiling over eruptions with the generation of huge volumes of pyroclastic density currents (Barranca Blanca and Carachi ignimbrites). The source of these eruptions remains unknown. ii) The Campo de la Piedra Pómez eruptive epoch (Upper Pleistocene), represented by the homonymous synthem and formed by at least one boiling over, explosive eruption. This eruption had two main eruptive phases represented by synthems UI and UII and was characterized by the generation of huge volumes of pyroclastic density currents (Ignimbrita Campo de la Piedra Pómez). A preliminary model is proposed in which the Campo de la Piedra Pómez eruptive epoch is associated with a volcano-tectonic depression. iii) The Cerro Blanco eruptive epoch (Holocene), represented by the homonymous synthem which includes the pre-, syn-and post-Cerro Blanco Caldera collapse (subsynthems CB1, CB2 and CB3 respectively). The pre-caldera activity was effusive and is indirectly represented by block and ash flow deposits. The syn-caldera activity was explosive with a plinian/subplinian eruptive style with simultaneous pyroclastic density currents generation, represented by Cerro Blanco Ignimbrite and associated pyroclastic fall deposits. The post-caldera activity was effusive/explosive and is represented by post-caldera domes and associated block and ash and vulcanian fall deposits. The results indicate that over the past 100000 years the Cerro Blanco Volcanic Complex had at least two large-scale eruptions (Volcanic Explosivity Index ≥ 6). Particularly, the caldera-forming Cerro Blanco eruption constitutes one of the greatest Holocene volcanic events in the Central Andes. Finally, the results presented in this study could contribute to the evaluation of the potential hazard associated with a possible renewal of explosive activity at Cerro Blanco Volcanic Complex
Thermobarometry applied to the long-lived Cordillera de San Buenaventura volcanic complex in Central Andes. Part I: Supra-solidus phase equilibria modelling
No full textThe long-lived Neogene-Holocene Cordillera de San Buenaventura (CSB) volcanic system in Southern Puna (NW Argentina), represents a valuable archive of information for the understanding of eruptive behaviors and magma dynamics and to decipher the anatomy of the trans-crustal plumbing system from the depth of the reservoir to the subsurface magmatic plexus. The CSB is characterized by cyclic mafic-intermediate eruptive styles, spanning from lava flows to caldera-forming events with a nearly continuous compositional series of erupted material from basaltic trachyandesites to high-silica rhyolites. For this reason, the CSB has recently been the focus of petrological studies through a general approach integrating textural observation and conventional thermobarometric models. However, due to intrinsic limits of the formulations, conventional models are not able to define either the P-T conditions of the solidus reaction nor the extent of the pre-eruptive supra-solidus environment. Moreover, conventional models cannot reconstruct either the amount or composition of the residual liquids at given pre-eruptive P-T values. Consequently, the published reconstructions and conceptual models that focus on the pre-eruptive state of the magmatic system are poorly constrained. To address this, the application of forward modelling thermobarometry based on the P-T-X pseudosection methods could represent an effective approach to better-constrain the pre-eruptive supra-solidus environment, to independently assess the effectiveness of thermobaric estimates from conventional modelling, and to evaluate if the modelled raw whole-rock composition is representative or not of the relic pre-eruptive magmatic equilibrium
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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