Estimación de la temperatura basal del “Glaciar Norte” del volcán Citlaltépetl, México. Modelo para determinar la presencia de permafrost subglaciar

The conditions of temperature and the “Glaciar Norte” ice conductivity in the Citlaltepetl volcano are studied with the aim to determinate its basal permafrost. From temperature records close to surface, the temperature average in internal steady-state of “Glaciar Norte” was estimated using a sinusoidal method, which manage the thermal-conductive properties of ice. Through its temperature profile, an approach to the thermal conditions of Mexico´s main glacier was obtained. The results may suggest the existence of a basal permafrost, which would be due to the ice insulation and the thermal conduction by direct contact between ice and substratum.Se estudian las condiciones de temperatura y la conductividad del hielo del “Glaciar Norte” del volcán Citlaltépetl con el objeto de determinar la existencia de permafrost basal. A partir de registros de temperatura cercanos a la superficie se estimó la temperatura media en estado estacionario del interior del “Glaciar Norte” mediante un método sinusoidal que utiliza las propiedades termo-conductoras del hielo. A través de su perfil de temperatura se obtuvo una aproximación a las condiciones térmicas del principal glaciar de México. Los resultados podrían sugerir la existencia de un permafrost basal, el cual sería producto del aislamiento del hielo y de la conducción térmica por contacto directo entre el hielo y el substrato

Evaluación del peligro por lahares en el flanco NE del volcán Popocatepetl

El presente trabajo muestra los resultados de la evaluación probabilística del peligro por lahares en la población de Santiago Xalitzintla, localizada en Puebla, en el flanco NE del volcán Popocatépetl, México, usando el programa para el modelado de lahares TITAN2F. Con el fin de evaluar la confiabilidad de su uso sobre un modelo de elevación, se compararon los pronósticos del programa con datos de campo del evento lahárico de 2001. Los resultados obtenidos con TITAN2F son comparables con la información generada por estudios de este lahar, permitiendo concluir que el modelado con TITAN2F es confiable. Esta investigación presenta una herramienta útil en el conocimiento del peligro por lahares, en la cual, además de presentar la probabilidad del área de afectación por inundación, se muestra la distribución de probabilidades para niveles de presión dinámica, parámetro útil en la evaluación de riesgos por flujos laháricos. Para realizar un análisis probabilístico, son necesarios un número de escenarios que sean estadísticamente representativos y abarquen todos los casos posibles. Con base en el registro de eventos históricos se definieron dos posibles fuentes para este tipo de flujos correspondientes a las barrancas Huiloac y Alseseca. En cada una de las cuencas se definieron los escenarios hipotéticos identificados por los rangos de condiciones iniciales (velocidad, concentración y volumen) que requiere TITAN2F. Para el análisis probabilístico se realizó un muestreo estratificado mediante el método Hipercúbico Latino (LHS), con el cual se obtiene una muestra representativa con cientos de combinaciones de las condiciones iniciales, las cuales se modelan con TITAN2F. El análisis probabilístico se hace mediante inferencia bayesiana, a través de rutinas de programación en OCTAVE. La distribución probabilística señala que las zonas comunitarias de Santiago Xalitzintla tienen una probabilidad cercana al 80 % de ser alcanzadas por el lahar, pero con bajos niveles de presión dinámica. Se identifica como zona crítica la desembocadura de la Barranca Huiloac en donde la probabilidad de que las presiones dinámicas superen niveles destructivos es alta

Evaluación de la vulnerabilidad de edificaciones ante la génesis de lahares: Caso de estudio en la población de Santiago Xalitzintla, en el flanco NE del volcán Popocatépetl (México)

Se analiza la vulnerabilidad estructural a partir de presiones dinámicas debidas al impacto por lahares en la población de Santiago Xalitzintla (México). El proceso de determinación de la vulnerabilidad se realizó de manera independiente a la amenaza (lahar), razón por la cual, se hizo una clasificación para todas y cada una de las construcciones. La tipificación se desarrolló teniendo en cuenta los materiales empleados en la construcción de las edificaciones, y cuánto éstos aportan a su resistencia, de dos maneras. a) Mediante trabajo de campo, con el fin de identificar las características estructurales y las posibles zonas críticas en el lugar. b) Utilizando la herramienta Street Viewde Google Earth como complemento, ya que por diversos factores limitantes durante el reconocimiento directo, no fue posible la identificación de la totalidad de las estructuras. La vulnerabilidad se estableció de manera semi-cuantitativa, teniendo como base varios estudios que permitieron elaborar un mapa de vulnerabilidad estructural ante daño total para la población, donde se identificó que el 62 % de las edificaciones poseen una vulnerabilidad baja, el 16 % una vulnerabilidad media y el 12 % una vulnerabilidad alta. Sin embargo, no se lograron identificar algunas construcciones (aproximadamente el 10 % del total) a las cuales se les asignó el rotulo “sin datos”. Mediante el empleo de curvas de probabilidad de destrucción total se elaboraron potenciales situaciones para Santiago Xalitzintla. En éstas, se evidencia que la probabilidad de destrucción total de las estructuras, según su tipología, cambia de acuerdo a las presiones dinámicas, con lo cual es posible evaluar diferentes escenarios de vulnerabilidad en la localidad

Un sistema automatizado de pronóstico de dispersión de cenizas y su monitoreo en tiempo real para el volcán Popocatépetl

El volcán Popocatépetl ha estado muy activo desde el 21 de diciembre de 1994. Su actividad, a lo largo de los casi 30 años de actividad eruptiva ha sido de carácter explosivo (principalmente de tipo vulcaniano), alternado con actividad efusiva (construcción de domos de lava). La actividad explosiva ha producido columnas de cenizas con diferentes tamaños, de hasta ~20 km de altitud y con una dispersión que ha llegado hasta los EUA. Sin embargo, la lluvia de cenizas importante se ha restringido a los ~65 km alrededor del cráter con evidencias de caída de cenizas en las ciudades de México y Puebla principalmente. El monitoreo de la actividad eruptiva ha sido llevado a cabo por el Centro Nacional de Prevención de Desastres, conjuntamente con investigadores de la Universidad Nacional Autónoma de México, principalmente del Instituto de Geofísica, durante los años que lleva en actividad el volcán. Este monitoreo ha consistido principalmente en la vigilancia sísmica, la deformación, las emisiones de gases volcánicos y el monitoreo de aguas de manantiales cercanos, entre otras líneas de trabajo

Breathing and Coughing: The Extraordinarily High Degassing of Popocatépetl Volcano Investigated With an SO2 Camera

How do lava domes release volcanic gases? Studying this problem is crucial to understand, and potentially anticipate, the generation of the sudden and dangerous explosive eruptions that frequently accompany dome extrusions. Since its awakening in 1994, Popocatépetl volcano has produced more than 50 lava domes and has been consistently among the strongest permanent emitters of volcanic gases. In this work, we have characterized the passive and explosive degassing between 2013 and 2016 at a high time resolution using an SO2 camera, to achieve a better understanding of the conduit processes. Our 4-year average SO2 flux is 45 kg/s, in line with the long-term average of the whole current eruptive period. We show that Popocatépetl volcano is essentially an open system and that passive degassing, i.e., degassing with no associated emission of lava or ash, dominates >95% of the time. This passive degassing is continuous and sustained, whether the crater contains a lava dome or not. It shows most of the time a strong periodic component, with a pseudo-period of ~5 min, and amplitudes of 30 to 60% of the average value. We could distinguish two types of explosions based on their SO2 flux patterns. The first type (E1) occurs in the middle of the normal passive degassing and is followed by a rapid return of the SO2 flux down to its pre-explosive level. The second type (E2), which corresponds to the strongest events, is anticipated by a rapid decrease of the SO2 flux to abnormally low values and is followed by a return to its normal values. The E2 explosions are probably caused by the accumulation of gas below a rapidly compacting permeable dome. We suggest that transient episodes of gravitational compaction of the usually permeable dome and the upper conduit is the only mechanism that is fast enough to explain the sharp decrease of the SO2 flux that anticipates the E2 explosions. Our model is potentially applicable to a large number of andesitic volcanoes that undergo passive degassing interspersed with short-lived explosions

Diurnal and seasonal active layer and permafrost dynamics from boreholes of the Latin American permafrost network

Permafrost is present in the high-altitude mountains of the Trans-Mexican Volcanic Belt as well as the Andes, even in the extreme dry Atacama highland. The permafrost and active layer termal state are characterized at Latin American Permafrost Network study sites. Ice rich or extremely dry permafrost was observed during drilling operations from Mexico (Pico de Orizaba, 5636m a.s.l. Iztaccíhuatl, 5230m a.s.l.), Colombia, Ecuador (Chimborazo, 6263m a.s.l.), Peru (Coropuna 5250 m a.s.l., Ampato 5850 m a.s.l., Chachani 5600 m a.s.l.) including the highest human habitation in the world: La Rinconada 5100 m a.s.l., Bolivia (Chacaltaya 5300 m a.s.l. where glacier disappeared in 2005), and the Chilean/Argentinian border (up to 6750 m a.s.l. including Parinacota, Aucanquilcha, Ojos del Salado, Llullaillaco, Tupungato and Tupungatito). The Lower Limit of Alpine Permafrost (LLAP) is redrawn from this study between latitude 19˚N and 40˚S where it is mainly in the tropical and arid Andes. This is not a rock glacier monitoring program that not mapping sporadic permafrost, but continuous permafrost terrains for long term temperature monitoring and understanding for local hydrological problems such as glacier/snow melt runoff or sublimation rate of higher elevations. The maximum active layer is typically influenced by the diurnal fluctuations which is between 12-30 cm deep however, maximum 2m depth of the seasonal active layer was observed at Ojos del Salado near the LLAP (5200 m a.s.l.). Daily severe frost shattering occurs near the ground surface, producing a dusty, fine-material horizon at an active layer near the LLAP, however a few freeze-thaw actions are higher than 6400 m. The snow-covered periods are important for providing protection from strong tropic solar radiation

The first two Meetings of Latin American Volcano Observatories (Encuentro de Observatorios Vulcanológicos de Latinoamérica)

The development of volcanology in Latin America is marked by a common regional scenario, with countries sharing borders, socio-cultural characteristics and facing similar scientific challenges. This scenario illustrates the need to create and promote regional networks. In this abstract we present the Jóvenes Volcanólogos Latinoamericanos (JVLA) network, a specific strategy that gathers early career volcanologists from Latin America and aims to strengthen volcanology in the region by encouraging the active participation of new generations. A benchmark in the construction of this network was the CoV9 conference (2016, Chile), where the 1st meeting of Young Latin American Volcanologists took place. As a response to the needs identified during that meeting, JVLA, together with the Asociación Latinoamericana de Volcanología (ALVO), developed an internship program in volcano observatories for highly motivated Latin American volcanology students. In addition to offering the young volcanologists scientific training and experience working in a volcano observatory, this program aims to promote the interaction and cooperation between universities and observatories. With the financial support of IAVCEI, a pilot test of the program will be carried out during the 2018 austral winter at the Observatorio Volcanológico de los Andes del Sur (OVDAS), in Chile. Among other actions, JVLA has been using social media and specialized newsletters (i.e., Gaceta ALVO and IAVCEI Newsletter) to distribute relevant information and to share personal experiences. Recently, on 25 April 2018, JVLA organized the 2nd Meeting of Young Latin American Volcanologist in Arequipa, Peru. In the future, the JVLA network expects to continue promoting new activities and initiatives (e.g., meetings, summer schools, internship programs) that strengthen the bonds between the new generations of Latin American volcanologists and to enhance the development of volcanology at a regional, and consequently, world-wide scale

The eruptive history of the Tequila volcanic field, western Mexico: ages, volumes, and relative proportions of lava types

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47808/1/445_2005_Article_434.pd

Synoptic analysis of a decade of daily measurements of SO2 emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change

Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality