Cotopaxi volcano, Ecuador, experienced notable restlessness in 2015 that was a major deviation from its normal background activity. Starting in April and continuing through November 2015 strong seismic activity, infrasound registry, hikes in SO 2 degassing and flank deformation with small displacements were some of the geophysical anomalies that were registered. Obvious superficial changes, such as small hydromagmatic eruptions, emission of vapor and ash columns, thermal hotspots around the crater and in nearby orifices and exacerbated glacier melting were also observed. Our contribution provides an overview of the 2015 Cotopaxi unrest by presenting the patterns of geophysical data and the sequence of events produced by the volcano. Cotopaxi's last important VEI 4 eruption was in 1877. Then it had devastating effects because of the transit of huge lahars down 3 major drainages. Comparatively, the 2015 activity never surpassed a magnitude VEI 2 and principally produced limited hydromagmatic explosions and semi-continuous low energy emissions and light ashfalls. Given the potential of major destruction from a large Cotopaxi eruption it is important to understand the geophysical fingerprints that characterized the 2015 episode with an eye to identifying onset of future restless periods. Overall, the monitoring activities, the data interpretation, formulation of reasonable eruptive scenarios, and finally, the preparation of a stream of constant information being relayed to concerned authorities and the public, was a real test of the IGEPN's capacity to deal with a complicated eruption situation whose outcome was not apparent at the beginning, but which concluded in a very small eruptive episode.
ResumenEn 2015 el volcán Cotopaxi, Ecuador experimento un notable cambio, que fue una desviación importante de su actividad normal de base. A partir de abril y hasta noviembre de 2015 fuerte actividad sísmica, registros de infrasonido, incremento en la desgasificación de SO 2 y pequeños cambios en la deformación de los flancos fueron algunas de las anomalías geofísicas registradas. Evidentes cambios superficiales también fueron observados como pequeñas erupciones hidromagmaticas, emisión de vapor, columnas de cenizas, puntos calientes alrededor del cráter y el deshielo de los glaciares. Nuestra contribución proporciona una visión general de las anomalías del Cotopaxi en el 2015, mediante la presentación de patrones de los datos geofísicos y la secuencia de eventos producidos por el volcán. La última erupción importante del Cotopaxi fue un VEI 4 en 1877. Esta tuvo efectos devastadores debido al descenso de enormes lahares por sus tres drenajes mayores. Comparativamente, la actividad del año 2015 nunca superó una magnitud VEI 2, principalmente produciendo explosiones hidromagmaticas, escasas emisiones y leves caídas de ceniza. Debido a la potencial destrucción por una eventual erupción grande del Cotopaxi es importante entender los registros geofísicos que caracterizó el episodio de 2015 para poder identificar el inic...