Multiple melt bodies fed the AD 2011 eruption of Puyehue-Cordon Caulle, Chile

Artículo de publicación ISIWithin the volcanological community there is a growing awareness that many large-to smallscale, point-source eruptive events can be fed by multiple melt bodies rather than from a single magma reservoir. In this study, glass shard major-and trace-element compositions were determined from tephra systematically sampled from the outset of the Puyehue-Corden Caulle (PCC) eruption (similar to 1 km(3)) in southern Chile which commenced on June 4th, 2011. Three distinct but cogenetic magma bodies were simultaneously tapped during the paroxysmal phase of this eruption. These are readily identified by clear compositional gaps in CaO, and by Sr/Zr and Sr/Y ratios, resulting from dominantly plagioclase extraction at slightly different pressures, with incompatible elements controlled by zircon crystallisation. Our results clearly demonstrate the utility of glass shard major-and trace-element data in defining the contribution of multiple magma bodies to an explosive eruption. The complex spatial association of the PCC fissure zone with the Liquine-Ofqui Fault zone was likely an influential factor that impeded the ascent of the parent magma and allowed the formation of discrete melt bodies within the sub-volcanic system that continued to independently fractionate.Argentine PIP CONICET 2011 0311 FONCYT PICT 2010 2046 Iniciativa Cientifica Milenio grants P02-51 NC120066 Chilean Fondecyt 115146

An 18,000 year-long eruptive record from Volcán Chaitén, northwestern Patagonia:Paleoenvironmental and hazard-assessment implications

The 2008 eruption of Volcán Chaitén (VCha) in northwestern Patagonia was the first explosive rhyolitic eruption to have occurred within a century and provided an unprecedented scientific opportunity to examine all facets of the eruption ranging from magma rheology/ascent rates to ash-fall effects on biota and infrastructure. Up to very recently it was thought that the latest eruption prior to the 2008 event occurred c. 9750 cal. a BP. Although a number of researchers have recognised additional eruptive products, but their stratigraphy, age, and geochemical attributes have not been systematically described and/or recorded. In this study, we provide a detailed examination of andic cover-beds and tephra-bearing lake sequences located both proximally and distally to VCha, which record a series of hitherto unknown rhyolitic eruptive products and place all previous observations firmly within a coherent stratigraphic framework. Through major- and trace-element glass shard geochemistry we are able to confidently verify eruptive source. A total of 20 discrete tephra beds are recognised, with at least 10 having widespread areal distributions and/or depositional imprints broadly comparable to, or greater than, the 2008-tephra event. This record indicates that VCha has been continuously but intermittently active as far back as the end of the Last Glacial Maximum (c. 18,000 cal a BP) with two dominant, genetically related magma types and an intermediary ¿mixed¿ type. Before this the eruptive record has been largely obscured and/or erased by widespread Andean piedmont glaciation. However, based on the tempo of VCha activity over the last c. 18,000 years, older VCha eruptives can be anticipated to occur as well as future hazardous explosive events. The new eruptive inventory will ultimately be useful for correlating equivalent-aged sequences and refining long-term eruptive tempo as well as corresponding temporal changes in magmatic evolution

The development and validation of an urbanicity scale in a multi-country study

Background : Although urban residence is consistently identified as one of the primary correlates of non-communicable disease in low- and middle-income countries, it is not clear why or how urban settings predispose individuals and populations to non-communicable disease (NCD), or how this relationship could be modified to slow the spread of NCD. The urban–rural dichotomy used in most population health research lacks the nuance and specificity necessary to understand the complex relationship between urbanicity and NCD risk. Previous studies have developed and validated quantitative tools to measure urbanicity continuously along several dimensions but all have been isolated to a single country. The purposes of this study were 1) To assess the feasibility and validity of a multi-country urbanicity scale; 2) To report some of the considerations that arise in applying such a scale in different countries; and, 3) To assess how this scale compares with previously validated scales of urbanicity. Methods : Household and community-level data from the Young Lives longitudinal study of childhood poverty in 59 communities in Ethiopia, India and Peru collected in 2006/2007 were used. Household-level data include parents’ occupations and education level, household possessions and access to resources. Community-level data include population size, availability of health facilities and types of roads. Variables were selected for inclusion in the urbanicity scale based on inspection of the data and a review of literature on urbanicity and health. Seven domains were constructed within the scale: Population Size, Economic Activity, Built Environment, Communication, Education, Diversity and Health Services. Results : The scale ranged from 11 to 61 (mean 35) with significant between country differences in mean urbanicity; Ethiopia (30.7), India (33.2), Peru (39.4). Construct validity was supported by factor analysis and high corrected item-scale correlations suggest good internal consistency. High agreement was observed between this scale and a dichotomized version of the urbanicity scale (Kappa 0.76; Spearman’s rank-correlation coefficient 0.84 (p < 0.0001). Linear regression of socioeconomic indicators on the urbanicity scale supported construct validity in all three countries (p < 0.05). Conclusions : This study demonstrates and validates a robust multidimensional, multi-country urbanicity scale. It is an important step on the path to creating a tool to assess complex processes like urbanization. This scale provides the means to understand which elements of urbanization have the greatest impact on health

The spatial structure of lithic landscapes : the late holocene record of east-central Argentina as a case study

Fil: Barrientos, Gustavo. División Antropología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Catella, Luciana. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Oliva, Fernando. Centro Estudios Arqueológicos Regionales. Facultad de Humanidades y Artes. Universidad Nacional de Rosario; Argentin

Multiple melt bodies fed the AD 2011 eruption of Puyehue-Cord\uf3n Caulle, Chile

Within the volcanological community there is a growing awareness that many large- to small-scale, point-source eruptive events can be fed by multiple melt bodies rather than from a single magma reservoir. In this study, glass shard major- and trace-element compositions were determined from tephra systematically sampled from the outset of the Puyehue-Cord\uf3n Caulle (PCC) eruption ( 3c1 km3) in southern Chile which commenced on June 4th, 2011. Three distinct but cogenetic magma bodies were simultaneously tapped during the paroxysmal phase of this eruption. These are readily identified by clear compositional gaps in CaO, and by Sr/Zr and Sr/Y ratios, resulting from dominantly plagioclase extraction at slightly different pressures, with incompatible elements controlled by zircon crystallisation. Our results clearly demonstrate the utility of glass shard major- and trace-element data in defining the contribution of multiple magma bodies to an explosive eruption. The complex spatial association of the PCC fissure zone with the Liqui\uf1e-Ofqui Fault zone was likely an influential factor that impeded the ascent of the parent magma and allowed the formation of discrete melt bodies within the sub-volcanic system that continued to independently fractionate

Cost Effectiveness of Bemiparin Sodium versus Unfractionated Heparin and Oral Anticoagulants in the Acute and Long-Term Treatment of Deep Vein Thrombosis

Introduction: Low-molecular-weight heparins (LMWHs) are at least as effective and well tolerated as unfractionated heparin (UFH) in the treatment of deep vein thrombosis (DVT), offering easier administration and obviating the need for anticoagulant monitoring, but have a higher acquisition cost than UFH. Objective: To quantify the potential economic impact of two regimens of subcutaneous bemiparin 115 IU/kg/day for 7-10 days (plus oral anticoagulants [OAC] or followed by long-term bemiparin 3500IU) versus dose-adjusted intravenous UFH for 7 days plus OAC for 3 months in the acute and long-term treatment of DVT. The representative patient was a 62-year-old, 77kg male with proximal DVT of the lower limbs. Methods: A cost-effectiveness analysis was performed using a decision-tree modelling approach. The results were expressed in terms of costs (_, 2002 values) and incremental cost effectiveness. The treatment costs (hospital stay, physician services, drug administration) and costs incurred due to complications (pulmonary embolism, recurrent DVT, bleeding events, thrombocytopenia and deaths) during the 3-month study period were considered for the primary analysis. Life expectancy and QALYs were considered for the secondary analysis. The study was performed in the setting of the Spanish National Health System. Results: Bemiparin plus OAC or long-term bemiparin for 3 months provided net cost savings of _769 and _908 per patient, respectively, compared with UFH plus OAC (UFH plus OAC _4128 vs bemiparin plus OAC _3359 vs long-term bemiparin _3220). Bemiparin plus OAC and long-term bemiparin for 3 months were calculated to avoid 27 and 7 additional VTE events, respectively, per 1000 patients treated. Bemiparin plus OAC or long-term bemiparin increased quality-adjusted life expectancy by approximately 1.72 and 0.74 years, respectively, compared with UFH plus OAC. The univariate sensitivity analysis supported the cost effectiveness of bemiparin in all the ranges tested for complications and costs. Conclusions: Our model suggests that bemiparin plus OAC or long-term bemiparin for 3 months may be dominant strategies over UFH plus OAC in the treatment of DVT from the Spanish National Health System perspective, offering better outcomes and cost savings. Long-term bemiparin may be a cost-neutral alternative to bemiparin plus OAC.Anticoagulants, Bemiparin-sodium, Cost-effectiveness, Cost-utility, Deep-vein-thrombosis, Heparin, Thromboembolism

Evacuations and Other Impacts from Large Ash Producing Eruptions: Perspectives from Patagonia

Overview: Impacts from large silicic eruptions in Patagonia (southern South America) Evacuations Infrastructure disruption Agricultural impacts Is it possible to identify vulnerability thresholds? Managing volcanic ash risk...some perspective

A past-millennium maximum in postglacial activity from Volc\ue1n Chait\ue9n, southern Chile

Volc\ue1n Chait\ue9n (southern Chile, ~43\ub0S) initiated an historically unprecedented eruption in A.D. 2008, surprising the local inhabitants, Chilean and Argentine authorities, and the geologic community. Available data at the time indicated an absence of explosive eruptions from this rhyolitic volcano since a large-magnitude eruptive event dated at ca. 10,500 yr B.P. We present lake-sediment data from Lago Teo, a small closed-basin lake located in the immediate vicinity of both Chait\ue9n township and the volcano, that spans the past ~10,000 yr and contains 26 pyroclastic fallout deposits. Glass-shard electron microprobe analyses revealed ten rhyolitic tephras indistinguishable in composition from the 2008 Volc\ue1n Chait\ue9n eruption, and ten others potentially derived from the Michinmahuida volcanic complex. Among the rhyolites, we detected three closely spaced tephras deposited between ca. 9460 and 9680 yr B.P., followed by two thick tephras dated at ca. 7700 and ca. 5080 yr B.P. Three other closely spaced tephras occur between ca. 600 and 850 yr B.P., the most recent prehistoric event at ca. 420 yr B.P., and a 3-cm-thick tephra deposited during the 2008 event. We calculate a median recurrence of ~310 yr between eruptive events from all sources over the past ~10,000 yr, and ~200 yr between Volc\ue1n Chait\ue9n events over the past millennium. Our results not only challenge the notion of an ~10,500-yr-long quiescence for Volc\ue1n Chait\ue9n activity, but also suggest that the 2008 eruption was an overdue phenomenon in the context of its postglacial eruptive history, illustrating the advantage and absolute necessity of utilizing lake-sediment archives for developing continuous well-dated time series inventories of explosive volcanic events

Impact of the 1960 major subduction earthquake in Northern Patagonia (Chile, Argentina)

The recent sedimentation processes in four contrasting lacustrine and marine basins of Northern Patagonia are documented by high-resolution seismic reflection profiling and short cores at selected sites in deep lacustrine basins. The regional correlation of the cores is provided by the combination of ¹³⁷Cs dating in lakes Puyehue (Chile) and Frías (Argentina), and by the identification of Cordon Caulle 1921–22 and 1960 tephras in lakes Puyehue and Nahuel Huapi (Argentina) and in their catchment areas. This event stratigraphy allows correlation of the formation of striking sedimentary events in these basins with the consequences of the May–June 1960 earthquakes and the induced Cordon Caulle eruption along the Liquiñe-Ofqui Fault Zone (LOFZ) in the Andes. While this catastrophe induced a major hyperpycnal flood deposit of ca. 3×10⁶ m³ in the proximal basin of Lago Puyehue, it only triggered an unusual organic rich layer in the proximal basin of Lago Frías, as well as destructive waves and a large sub-aqueous slide in the distal basin of Lago Nahuel Huapi. A very recent mega-turbidite in the two distal basins of Reloncavi fjord located close to the LOFZ suggests that 1960 co-seismic movements in this area may have triggered the remobilization of ca. 187×10⁶ m³ of marine sediments