Effusive pulse at El Reventador volcano, October 2025: Andesitic lava flow and lava front collapse-induced pyroclastic density currents

El Reventador, one of Ecuador’s most active volcanoes, has experienced near-continuous eruptive activity since 2002. In 2025, beginning on 3 October, summit explosive activity declined sharply. On 6 October, continuous gas emissions increased and a lava flow from the east-southeast vent began advancing. Over the following days, SO2 emissions were detected by satellite, while the summit explosion rate and seismic noise plummeted. On 12 October, a prolonged collapse of the lava flow front triggered pyroclastic density currents (PDCs) with runouts of up to 2.25 km, the longest observed at the volcano since 2017. The effusive pulse, which produced approximately 2.8–3.2 million m3 of andesitic lava, ended by 28 October, when explosive activity resumed. This episode highlighted the importance of multiparametric monitoring and targeted fieldwork to track eruptive transitions, reconstruct eruption dynamics, and improve hazard assessment and early warning in remote volcanic regions.