Artículo de publicación ISILakes formed in the Aysén region of southern Chile after the retreat of mountain glaciers, established by ~17,900 calendar years before present (cal years BP) or earlier, contain numerous late-glacial and Holocene tephra layers derived from >70 eruptions of the volcanoes in the region, including Hudson, the southernmost in the Andean Southern Volcanic Zone (SVZ). Sediment cores fromseven of these lakes contain an unusually thick late-glacial age tephra layer, which based on its distribution and bulk trace-element composition was derived from a large explosive eruption of Hudson volcano between 17,300 and 17,440 cal years BP and is termed Ho. In 13 cores from six of these lakes, each located ~100 km generally northeast of Hudson, the Ho tephra layer ranges between 50 and 88 cm in thickness, and contains pumice grains up to 2 cm in maximum diameter. Comparison with three previously documented large explosive Holocene Hudson eruptions (H1 at 7,750 cal years BP, H2 at 3,920 cal years BP, and H3 in 1991 AD) suggests that Ho was larger, with an estimated tephra volume of >20 km3, the largest post-glacial eruption documented for any volcano in the southern Andes and most likely responsible for the formation of the Hudson caldera. In total, Hudson has erupted ≥45 km3 of pyroclastic material in the last ~17,500 years, making it the most productive volcano in the southern Andes in terms of the total volume erupted since the beginning of deglaciation in the region. Chemical stratification is not seen in the waterlain Ho tephra, but these deposits are bi-modal, consisting of a much greater proportion of dark glassy basaltic-trachyandesite dense fragments and pumice, with glasses which range between 55 and 59 wt.% SiO2, along with volumetrically lesssignificant lighter-colored trachydacite pumice, with glass of 66 wt.% SiO2. In contrast, H1 products are trachyandesitic in composition, H2 ones are more felsic than H1, being composed essentially of trachydacite, and although H3 1991 AD again produced tephra of bi-modal compositions, it erupted a much smaller proportion of mafic compared to felsic material than did Ho. Thus, the repetitive large explosive eruptions of Hudson volcano have evolved to progressively less-mafic overall compositions from late-glacial to historic times, and their volumes have decreased. Sr-isotopic composition of bulk samples of the most mafic dense glass and most felsic pumice components of the Ho tephra, as well as samples from other Hudson eruptions, which overall range from 51 to 66 wt.% SiO2, with 525 to 227 ppm Sr, are all similar (0.70444± 0.00007), indicating that crystal-liquid fractionation rather than crustal assimilation was the main process responsible for these chemical variations.This research was supported by Fondecyt (Chile) grant #1121141, the Institute of Ecology and Biodiversity grants ICM P05–002 and PFB-23, and the Department of Geological Sciences, CU-Boulder. We also would like to thank A. Vichick, T. Ni...
We conducted a lithological mapping of the Viedma volcano, one of five volcanoes in the Andean Austral Volcanic Zone (AVZ), using remote sensing techniques. We used data of the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) sensor which is highly effective in geological research, to understand build-up processes and to deduce compositional variation of the Viedma volcano emerging from the South Patagonian ice field. The volcanic edifice was divided into bright parts that mainly compose the eastern flank of the volcano and dark parts at the central crater area based on the observation in visible and near infrared ranges. The SiO 2 concentration was calculated using the bands in the visible and thermal infrared regions. The dark part and the bright part have approximately 51 wt% and 63 wt% average SiO 2 content respectively, indicating that the exposures of the Viedma volcano have a wide variation in SiO 2 concentration. Although, according to other authors, ejecta from the Viedma volcano have 64-66 wt% SiO 2 and other AVZ volcanoes are essentially monolithologic dacite/andesite volcanoes, the edifice of the Viedma volcano appears to be composed mostly of basalts or older rocks/basement with low silica contents. RESuMEN. Variaciones composicionales reveladas mediante análisis de imágenes ASTER del volcán Viedma, Zona Volcánica Andina Austral. Mediante el uso de técnica de sensoría remota se ha desarrollado un mapeo litoló-gico del volcán Viedma, uno de los cinco volcanes de la Zona Volcánica Andina Austral (ZVA). Para este efecto, se ha utilizado el radiómetro 'Advanced Spaceborne Thermal Emission and Reflection' (ASTER) que es muy efectivo en investigación geológica, para entender los procesos que han controlado la estructura y deducir las variaciones composi-cionales del volcán Viedma, que sobresale levemente de la superficie del campo de hielo Patagónico Sur. Sobre la base de la observación en el intervalo del espectro visible e infrarrojo cercano, en el edificio se distinguen partes brillantes que corresponden al flanco oriental del volcán y partes oscuras en el área del cráter central. La concentración de SiO 2 se calculó a través del uso de las bandas en las regiones visibles e infrarrojo termal. Las partes oscura y brillante tienen un promedio aproximado de 51% y 63% de SiO 2 en peso, respectivamente, lo que indica que el volcán Viedma expone una amplia diferenciación de las concentraciones de SiO 2. Aunque, según otros autores, las muestras analizadas de material piroclástico del volcán Viedma tienen contenidos de 64-66% SiO 2 y que otros aparatos de la ZVA son volcanes esencialmente monolitológicos dacíticos/andesíticos, el edificio del volcán Viedma estaría compuesto principalmente de basaltos o las rocas más antiguas de su basamento tienen un bajo contenido de sílice.
Neste artigo, pretendemos pensar o processo de produção industrial de imagens como parte de um programa de educação visual, cujas origens históricas antecedem o atual desenvolvimento industrial. Nossa hipótese é de que a valorização irrefletida da produção e do consumo de imagens através de aparelhos tecnológicos reproduz e intensifica a desvalorização dos sentidos na produção de conhecimento e revaloriza o pensamento "cartesiano", educando o olho a ver o homem e o mundo conforme as possibilidades e os limites destas formas de representação da realidade. A ausência de uma atitude crítica em relação aos processos de produção destas imagens e o desconhecimento de suas origens históricas fazem com que a escola incorpore, de forma conservadora, o programa de educação visual acima referido e eduque, de forma alienada, o olho a ver a realidade.
Este texto apresenta um estudo/relato de experiência de um método cartográfica que pretende refletir o fazer cinema com alunos de 8 a 11 anos (3º ao 5º ano da Educação Básica) de uma escola pública do interior do estado de São Paulo. O trabalho se deu por meio de oficinas dentro do programa Mais Educação do Governo Federal e tinham como objetivo a criação de territórios existenciais permeados de subjetividade e nuances, inspiradas em Manoel de Barros. As oficinas utilizaram diferentes dispositivos de criação de imagens, procurando replicar os gestos cinematográficos de escolha, disposição e ataque propostos por BERGALA. Esta experiência demonstrou que o encontro com o cinema na escola é um encontro com um “estrangeiro”, capaz de produzir conflitos estéticos e cognitivos, tensões criativas e muitos questionamentos que propiciam a invenção ou reinvenção da escola como espaço de práticas culturais democráticas.
En este trabajo se propone la solución de dos de los principales problemas que deben ser resueltos en las primeras etapas del proyecto de los parques eólicos, la estructura que deberá tener el parque y su rentabilidad. Se aplica un modelo matemático desarrollado a partir del método paramétrico que permite determinar de forma rápida y con aceptable precisión el costo capital mediante parámetros técnicos relevantes. El modelo fue calibrado mediante una base de datos representativa de los países de América Latina que mayor utilización hacen de la energía eólica. Se utilizó para definir la estructura más adecuada del proyecto de cinco parques en la provincia de Chimborazo, en Ecuador. Se concluye que el número de máquinas, sus potencias y alturas de las torres son los tres parámetros que determinan el costo del parque y al mismo tiempo, son los que definen la energía producida y la rentabilidad, por lo que un modelo de costo que integre esas variables resulta una importante herramienta cuando se aplican criterios de validación económicos-financieros como el Valor Presente Neto, el Costo nivelado de la Energía, el Costo del Ciclo de Vida y otros.
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