Magmatic connectivity among six Galápagos volcanoes revealed by satellite geodesy.

Shallow magmatic reservoirs that produce measurable volcanic surface deformation are often considered as discrete independent systems. However, petrological analyses of erupted products suggest that these may be the shallowest expression of extensive, heterogeneous magmatic systems that we show may be interconnected. We analyse time series of satellite-radar-measured displacements at Western Galápagos volcanoes from 2017 to 2022 and revisit historical displacements. We demonstrate that these volcanoes consistently experience correlated displacements during periods of heightened magma supply to the shallow crust. We rule out changes in static stress, shallow hydraulic connections, and data processing and analysis artefacts. We propose that episodic surges of magma into interconnected magmatic systems affect neighbouring volcanoes, simultaneously causing correlations in volcanic uplift and subsidence. While expected to occur globally, such processes are uniquely observable at the dense cluster of Western Galápagos volcanoes, thanks to the high rate of surface displacements and the wealth of geodetic measurements.

Forecasting mechanical failure and the 26 June 2018 eruption of Sierra Negra Volcano, Galápagos, Ecuador.

Using recent advancements in high-performance computing data assimilation to combine satellite InSAR data with numerical models, the prolonged unrest of the Sierra Negra volcano in the Galápagos was tracked to provide a fortuitous, but successful, forecast 5 months in advance of the 26 June 2018 eruption. Subsequent numerical simulations reveal that the evolution of the stress state in the host rock surrounding the Sierra Negra magma system likely controlled eruption timing. While changes in magma reservoir pressure remained modest (<15 MPa), modeled widespread Mohr-Coulomb failure is coincident with the timing of the 26 June 2018 moment magnitude 5.4 earthquake and subsequent eruption. Coulomb stress transfer models suggest that the faulting event triggered the 2018 eruption by encouraging tensile failure along the northern portion of the caldera. These findings provide a critical framework for understanding Sierra Negra's eruption cycles and evaluating the potential and timing of future eruptions.

Ecological consequences of post-Columbian indigenous depopulation in the Andean-Amazonian corridor.

European colonization of South America instigated a continental-scale depopulation of its indigenous peoples. The impact of depopulation on the tropical forests of South America varied across the continent. Furthermore, the role that indigenous peoples played in transforming the biodiverse tropical forests of the Andean-Amazonian corridor before AD 1492 remains unknown. Here, we reconstruct the past 1,000 years of changing human impact on the cloud forest of Ecuador at a key trade route, which connected the Inkan Empire to the peoples of Amazonia. We compare this historical landscape with the pre-human arrival (around 44,000-42,000 years ago) and modern environments. We demonstrate that intensive land-use within the cloud forest before European arrival deforested the landscape to a greater extent than modern (post-AD 1950) cattle farming. Intensive indigenous land-use ended abruptly around AD 1588 following a catastrophic population decline. Forest succession then took around 130 years to establish a structurally intact forest-one comparable to that which occurred before the arrival of the first humans to the continent. We show that nineteenth-century descriptions of the Andean-Amazonian corridor as a pristine wilderness record a shifted ecological baseline-one that less than 250 years earlier had consisted of a heavily managed and cultivated landscape.

Areas prone to slow slip events impede earthquake rupture propagation and promote afterslip.

At subduction zones, transient aseismic slip occurs either as afterslip following a large earthquake or as episodic slow slip events during the interseismic period. Afterslip and slow slip events are usually considered as distinct processes occurring on separate fault areas governed by different frictional properties. Continuous GPS (Global Positioning System) measurements following the 2016 Mw (moment magnitude) 7.8 Ecuador earthquake reveal that large and rapid afterslip developed at discrete areas of the megathrust that had previously hosted slow slip events. Regardless of whether they were locked or not before the earthquake, these areas appear to persistently release stress by aseismic slip throughout the earthquake cycle and outline the seismic rupture, an observation potentially leading to a better anticipation of future large earthquakes.

Aquatic community response to volcanic eruptions on the Ecuadorian Andean flank: evidence from the palaeoecological record.

Aquatic ecosystems in the tropical Andes are under increasing pressure from human modification of the landscape (deforestation and dams) and climatic change (increase of extreme events and 1.5 °C on average temperatures are projected for AD 2100). However, the resilience of these ecosystems to perturbations is poorly understood. Here we use a multi-proxy palaeoecological approach to assess the response of aquatic ecosystems to a major mechanism for natural disturbance, volcanic ash deposition. Specifically, we present data from two Neotropical lakes located on the eastern Andean flank of Ecuador. Laguna Pindo (1°27.132'S-78°04.847'W) is a tectonically formed closed basin surrounded by a dense mid-elevation forest, whereas Laguna Baños (0°19.328'S-78°09.175'W) is a glacially formed lake with an inflow and outflow in high Andean Páramo grasslands. In each lake we examined the dynamics of chironomids and other aquatic and semi-aquatic organisms to explore the effect of thick (> 5 cm) volcanic deposits on the aquatic communities in these two systems with different catchment features. In both lakes past volcanic ash deposition was evident from four large tephras dated to c.850 cal year BP (Pindo), and 4600, 3600 and 1500 cal year BP (Baños). Examination of the chironomid and aquatic assemblages before and after the ash depositions revealed no shift in composition at Pindo, but a major change at Baños occurred after the last event around 1500 cal year BP. Chironomids at Baños changed from an assemblage dominated by Pseudochironomus and Polypedilum nubifer-type to Cricotopus/Paratrichocladius type-II, and such a dominance lasted for approximately 380 years. We suggest that, despite potential changes in the water chemistry, the major effect on the chironomid community resulted from the thickness of the tephra being deposited, which acted to shallow the water body beyond a depth threshold. Changes in the aquatic flora and fauna at the base of the trophic chain can promote cascade effects that may deteriorate the ecosystem, especially when already influenced by human activities, such as deforestation and dams, which is frequent in the high Andes.

The response of vegetation on the Andean flank in western Amazonia to Pleistocene climate change.

A reconstruction of past environmental change from Ecuador reveals the response of lower montane forest on the Andean flank in western Amazonia to glacial-interglacial global climate change. Radiometric dating of volcanic ash indicates that deposition occurred ~324,000 to 193,000 years ago during parts of Marine Isotope Stages 9, 7, and 6. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest altered radically in response to glacial-interglacial climate change. The presence of Podocarpus macrofossils ~1000 meters below the lower limit of their modern distribution indicates a relative cooling of at least 5°C during glacials and persistence of wet conditions. Interglacial deposits contain thermophilic palms suggesting warm and wet climates. Hence, global temperature change can radically alter vegetation communities and biodiversity in this region.

Observación instrumental de lahares en el volcán Tungurahua entre abril - 2000 y agosto - 2001

La presencia de lahares ha sido una de las consecuencias de la fase eruptiva del volcan Tungurahua iniciada en octubre de 1999. dado que estos eventos resultan peligrosos en ciertos lugares del volcán, dos instrumentos de detección de lahares (Acoustic Flow Monitors) fueron instalados para la vigilancia de este tipo de fenómenos volcánicos. Los registros de los equipos instalados, recibidos en tiempo real, permitieron alertar sobre la presencia de lahares, así como pronosticar ciertas características del flujo. Además, estimar el volumen de material desalojado por cada periodo abril 2000- agosto 2001.(AU)

Estimaciones del volumen global del depósito de ceniza de la erupción de agosto del 2001 del volcán Tungurahua

La fase eruptiva relativamente intensa del volcán Tungurahua durante el mes de agosto del 2001 produjo un notable deposito de ceniza, ubicado principalmente al oeste del edificio. Se midió los espesores de la capa de ceniza en noventa sitios para establecer un mapa con doce isópacas. En este articulo, se presentan las estimaciones preliminares del volumen global del deposito de ceniza, las cuales fueron calculadas utilizando varios modelos propuestos recientemente en la literatura especializada. Según el modelo utilizado, los resultados obtenidos caen en el rango entre 3.3 a 8.75x10 m3. De estos valores podemos concluir que el índice de explosividad volcánica ("VEI") de la fase eruptiva de agosto del 2001 fue de 3. (AU)

Caracterización de los flujos piroclásticos producidos por el volcán Tungurahua (Ecuador) : Evidencias de dichos flujos en la ciudad de Baños

Los flujos piroclásticos han sido un fenómeno importante durante muchas de las erupciones del volcán Tungurahua. En este estudio se caracteriza los tres tipos de depósitos de flujos piroclásticos identificados en los alrededores del volcán, los cuales han tenido una clara incidencia en el pasado reciente. Al igual que el resto de flancos del volcán, el sitio del actual asentamiento de la ciudad de baños ha estado expuesto al impacto de estos fenómenos altamente destructivos. Sin embargo, hasta la fecha las evidencias de que el actual Baños ha sido afectado por flujos piroclásticos son escasas, a excepción de un relato histórico relativo a la erupción de 1773, en el cual se menciona que un flujo "caliente"afectó el valle del Río Vazcún e inclusive alcanzó el sitio de la antigua iglesia de Baños. Los trabajos en estratigrafía realizados recientemente en la ciudad de Baños muestran claramente la existencia de depósitos de flujos incandescentes en el actual casco urbano de la ciudad, los cuales fueron relacionados con erupciones importantes del Tungurahua. (AU)

El complejo volcánico Cayambe : Síntesis geológica, actividad holocénica y evaluación de los peligros volcánicos

El complejo volcánico Cayambe esta constituido por tres edificios: a) un antiguo edificio efusivo, el "Viejo Cayambe"; b) el volcán joven "Nevado Cayambe" caracterizado por una historia mucho mas compleja y dinamismos eruptivos más explosivos; c) un cono satélite construido en el extremo oriental del complejo, el "Cono de la Virgen". La actividad reciente del Nevado Cayambe (últimos 4000, aBP) ha presentado trees ciclos de actividad de 300, 600 y 900 años de duración, separados por periodos de calma de 600 y 1000 años respectivamente. El último periodo eruptivo, iniciado hace 100 años, se ha caracterizado por el crecimiento de domos de lava, la generación de flujos piroclásticos de colapso de domo, la producción de lahares asociados a la fusión del casquete glaciar y una limitada distribución de piroclastos. Una síntesis de estos de estos datos permite proponer un primer mapa de peligros volcánicos asociados a este volcán. (AU)

Manual de defensa civil para educadores ecuatorianos. Para la elaboración del plan de defensa civil ante desastres de planteles educativos / Manual of Civil Defense for Ecuadorian Educators. To Build the Civil Defense Plan Before Disasters in Educative Establishments

Acuerdo de institucionalización del Plan de Defensa Civil de Autoprotección ante Desastres.- Fenómenos naturales: sismos, erupciones volcßnicas, inundaciones, derrumbes y deslizamientos.- La Defensa Civil en el Ecuador.- Medidas de autoprotección.- Plan de defensa civil de autoprotección.- Elaboración del plan.- Anexos: Formato y modelo del Plan desarrollado