Thermal imaging and analysis of short-lived Vulcanian explosions at Volcán de Colima, Mexico

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Vulcanian explosions present a major hazard at many active volcanoes, but they also provide useful insights into the underlying behaviour of the volcanic system and therefore require close monitoring. Thermal infrared cameras are an effective tool for imaging Vulcanian explosion plumes since they capture detailed temperature information, and can reveal the internal dynamics of the plume-forming explosions. High spatial resolution thermal images of 200 small to moderate sized Vulcanian explosions from the summit crater of Volcán de Colima, Mexico, recorded between 2006 and 2011, were analysed to distinguish different event types and develop an explosion classification scheme. Explosions display a broad spectrum of sizes and characteristics, ranging between two typical end-members: “large-impulsive” events producing rapidly ascending explosion plumes up to heights of 600–1600m above the crater rim, and “small-diffusive” events with plumes restricted to heights <600m. Most explosion plumes comprise a steady “gas-thrust” feeder plume below a convecting plume front. Others, that lack sufficient kinetic energy, rise buoyantly throughout the explosion, with steady buoyant ascent velocities ranging from ~1ms−1 to ~29ms−1. A time-series of thermal imagery throughout the period 2006–2011 reveals a weak relationship between apparent plume temperatures and lava dome extrusion, with the highest explosion temperatures coinciding with the onset of dome growth in early 2007. Temporal variations in the source locations of explosions across the summit crater are also identified and appear to show a close relationship to the patterns of lava dome growth and thermal evolution, with explosion source locations associated with the highest temperature thermal features.