Chemical Signals in Tree Rings from Northern Patagonia as Indicators of Calbuco Volcano Eruptions since the 16th Century

The Calbuco volcano ranks third in the specific risk classification of volcanoes in Chile and has a detailed eruption record since 1853. During 2015, Calbuco had a sub-Plinian eruption with negative impacts in Chile and Argentina, highlighting the need to determine the long-term history of its activity at a high-resolution time scale to obtain a better understanding of its eruptive frequency. We developed a continuous eruptive record of Calbuco for the 1514–2016 period by dendrochemical analysis of Fitzroya cupressoides tree rings at a biennium resolution using inductively coupled plasma–mass spectrometry. After comparing the chemical record of 20 elements contained in tree rings with historical eruptions, one group exhibited positive anomalies during (Pb/Sn) and immediately after (Mo/P/Zn/Cu) eruptions, with a Volcanic Explosivity Index (VEI) ≥ 3, and so were classified as chemical tracers of past eruptions (TPE). The tree-ring width chronology also exhibited significant decreases in tree growth associated with eruptions of VEI ≥ 3. According to these records, we identified 11 new eruptive events of Calbuco, extending its eruptive chronology back to the 16th century and determining a mean eruptive frequency of ~23 years. Our results show the potential to use dendrochemical analysis to infer past volcanic eruptions in Northern Patagonia. This information provides a long-term perspective for assessing eruptive history in Northern Patagonia, with implications for territorial planning.

Microstructure and Durability Performance of Mortars with Volcanic Powder from Calbuco Volcano (Chile) after 4 Hardening Years

One of the most popular ways to lessen the impact of the cement industry on the environment consists of substituting clinker by additions. The service life required for real construction elements is generally long, so it would be interesting to obtain information about the effects of new additions after a hardening period of several years. Analyzed here are the effects of the incorporation of volcanic ashes, coming from Calbuco volcano’s last eruption (Chile), as clinker replacement, in the durability and pore structure of mortars, after approximately 4 hardening years (1500 days), in comparison with reference specimens without additions. The substitution percentages of clinker by volcanic powder studied were 10% and 20%. The microstructure was characterized with mercury intrusion porosimetry and impedance spectroscopy. In order to evaluate the pozzolanic activity of the volcanic powder after 1500 days, differential thermal analyses were performed. Water absorption after immersion, steady-state diffusion coefficient and length change were also studied. In accordance with the results obtained, the 10% and 20% substitution of clinker by volcanic powder from the Calbuco volcano showed beneficial effects in the mortars after 4 years, especially regarding the microstructure and chloride diffusion, without noticeable influence in their water absorption.

Petrology of the April 2015 Eruption of Calbuco Volcano, Southern Chile

Understanding the origin of intermediate magmas that commonly erupt from subduction zone volcanoes is important to better constraining the mechanisms of continental crust formation. We performed a detailed mineralogical and petrological study of the eruptive products from the April 2015 eruption of Calbuco volcano, Chile, a three-phase sub-Plinian eruption that produced pyroclastic deposits of andesitic composition. The eruptive products comprise a glass phase and a high but variable proportion of minerals dominated by plagioclase, clinopyroxene, and orthopyroxene, with minor olivine, amphibole, and magnetite. Plagioclase is very strongly zoned with highly anorthitic cores surrounded by more albitic rims, and no intermediate compositions between them. Based on thermodynamic calculations and published experimental data, we estimate that the anorthitic cores crystallized from a basaltic andesite melt containing 3·5–4·5 wt% H2O. The bulk-rock major and trace element variability at Calbuco is best explained by the accumulation of a variable amount of minerals (in relative proportion 72 % plagioclase, 28 % pyroxene) in a dacitic melt. These minerals most probably formed in the crystal mush zone of the magma chamber, at 200–300 MPa (8–11 km depth) according to pyroxene and amphibole compositions. A few weeks to months before the eruption, the crystal mush was disaggregated, perhaps owing to magmatic underplating, and a crystal-bearing dacitic melt migrated into a subsurface storage region where the albitic plagioclase rims crystallized. The eruption was probably internally triggered by over-pressurization in the shallow magma chamber.

Petrology of the April 2015 eruption of Calbuco volcano, southern Chile

<p>Understanding the origin of intermediate magmas that commonly erupt from subduction zone volcanoes is important to better constrain the mechanisms of continental crust formation. We carried out a detailed mineralogical and petrological study of the eruptive products from the last eruption of Calbuco volcano, Chile. In April 2015, Calbuco produced a 3 phase sub-Plinian eruption with pyroclastic fallouts and flows of andesitic composition. Rocks from Calbuco are made up of a glass phase and a high but variable proportion of minerals dominated by plagioclase, clinopyroxene, orthopyroxene and minor olivine, amphibole and magnetite. Plagioclase is very strongly zoned with highly anorthitic cores surrounded by more albitic rims. Based on thermodynamic calculations and using published experimental data, we estimate that the anorthitic cores crystallized from a basaltic andesite containing 3.5-4.5 wt.% H<sub>2</sub>O. Using geochemical modelling, we also estimate that the bulk-rock major and trace element variability of Calbuco is best explained by accumulation of minerals in proportion plagioclase/pyroxene 72/28 in a dacitic melt. Such minerals most likely formed in the crystal mush zone of a magma chamber which, according to pyroxene and amphibole compositions, may have formed at a pressure of 2-3 kbar, corresponding to a depth of 8-11 km. A few weeks to months before the eruption, the crystal mush disaggregated, perhaps due to magmatic underplating, and a crystal-bearing dacitic melt moved upwards into a sub-surface storage region where the anorthite-poor rims formed. The 2015 eruption was probably internally triggered by over-pressurization in the shallow magma chamber.</p>

Administrando la Comunicación de Riesgos en una Emergencia Sanitaria, “El caso de la erupción del Volcán Calbuco”, Chile 2015 = Managing the Risk Communication in a Health Emergency, "The case of the eruption of the Calbuco Volcano", Chile 2015

El siguiente trabajo presenta la estrategia comunicacional desarrollada por la institución Seremi de Salud, durante la emergencia sanitaria por la erupción del Volcán Calbuco (Región de Los Lagos, Chile) en abrildel 2015, para disminuir los riesgos en la salud de las personas y comunidades expuestas a la erupción.Se da cuenta de una estrategia preventiva e informativa a través de diversos materiales, incluyendo las redes sociales, además de la transparencia institucional en términos de información a la comunidad sobre calidad del aire, agua y ceniza. El análisis de las redes sociales institucionales (twitter) indica que los ejes discursivos sanitarios fueron adecuadamente apropiados y difundidos por la comunidad.Palabras clave: Salud pública; Comunicación de riesgos; Redes sociales en salud; Vigilancia ambiental; Vigilancia epidemiológica.AbstractThe following work presents the communicational strategy developed by the Health Seremi institution, during the health emergency due to the eruption of the Calbuco Volcano (Los Lagos Region, Chile) in April 2015, to diminish the risks of health for people and communities exposed to the eruption. A preventive and informative strategy was reported through various resources, including website social networks, as well as institutional transparency in terms of information towards the community regarding air quality, water and ash presence. The analysis of institutional social networks (twitter) indicates that the sanitary discursive cores were properly fitting and spread in this social network.Keywords: Public health; Risk communication; Health social network; Environmental monitoring; Epidemiological surveillance.