Location and setting: Ecuador; Eastern Cordillera of Ecuadorean Andes; composite continental-arc volcano
Background information: Cotopaxi is one of the largest and most hazardous stratovolcanoes in the Northern Andes with an andesitic and rhyolitic magmatic history. It is formed by a large symmetrical cone with 3000 m of relief and a 22 km basal diameter. Its upper flanks are covered by a glacier with a volume of 1.0 km3 approximately. Periodic alternation of rhyolitic and andesitic eruptions is clearly observed in the last eruptive period that started 13 ka ago. About 4,500 years ago a dome and sector collapse on Cotopaxi’s NE flank generated one of the largest cohesive debris flows, the Chillos Valley lahar. Recent eruptions have been characterized by lithic-rich pyroclastic flows, infrequent lava flows, andesitic lapilli and ash falls, and large debris flows.
Relevance to project: Cotopaxi with its bimodal magmatic composition, is one of the most active and hazardous volcanoes in Ecuador. Recent studies estimated an average recurrence of one explosive, lahar triggering event every 117 years over the last millennia. Cotopaxi has been monitored by the Instituto Geofisico since 1977. Since 2001 increased levels of seismicity and fumarolic activity has been observed and continue today. The current activity has major implications regarding heat transfer into Cotopaxi’s ice-cap with a potential for generation of catastrophic lahars.
Monitoring data available to consortium: 1988 - present: analogue seismic records; 1989: digital seismic records of a short period instrument; 1992 - present: short period digital records of a 4 station network; 2006 - present: continuous broad band seismic and infrasound data from a 5-station digital network; sporadic broad band data: one month in 2002, three months in 2007.