High-resolution video characterisation of vulcanian plumes at Sabancaya Volcano, Peru

Since November 2016, volcanic activity at Sabancaya volcano (Peru) has been characterized by multiple short-lived Vulcanian explosions per day. These Vulcanian-type explosions and related volcanic plumes were also recorded in visible light during July and August 2018. Specific objectives of this work are to: i) develop a new algorithm to identify and isolate the plume pixels; ii) extract the main geometrical parameters of the eruptive column, such as the height and width as a function of time; iii) determine quantitative information related to the plume motion (e.g. the rise velocity and air entrainment coefficient), based on the physical quantities obtained through the first-order analysis; iv) characterize the eruption dynamics of Vulcanian plumes at Sabancaya. The results show that the algorithm traces well the plume boundaries and is also capable of automatically calculating the geometrical parameters (height of the top, maximum width and rise velocity of the plume head). We focussed on 8 explosions that are characterized by optimal weather and plume rise conditions. The calculated height for these selected explosions ranges from 180 to 715 m within 30 seconds after ejection, while the exit velocities are up to 96.5 m/s. The air entrainment coefficients were also estimated, and lie around 0.15 ± 0.04. Moreover, we found that plumes at Sabancaya have a transient/thermal behaviour, dominated by an unsteady release of pyroclastic material that strongly controls its features and evolution. Thus, high resolution video analysis, quantitative measurements and numerical modelling are merged here to improve the understanding of volcanic explosions at Sabancaya volcano and of volcanic plumes in general.