Active volcano fumarole 6 volcanic eruption 6 Eruptive column 4 Peteroa Volcano 4 Plinia 4 Sup-plinian eruption 4 Tephra 4 Volcanic plume 4 crystal 4 plume 4 tephra 4 volcanic glass 4 Copahue 2 Copahue volcano 2 Fluid geochemistry 2 Geochemical monitoring 2 Hydrothermal system 2 Neuquen 2 Southern Volcanic Zone 2 carbon monoxide 2 chemical composition 2 geochemistry 2 hydrocarbon 2 hydrogen 2 hydrothermal system 2 isotopic composition 2 volcanic gas 2 Ciencias de la Tierra y Medio Ambiente 1 Copahue (Neuquén, Patagonia Argentina) 1