Linking electrical activity to explosive eruption styles during the 2021 Cumbre Vieja eruption

The 2021 Tajogaite eruption of Cumbre Vieja on the island of La Palma (Canary Islands, Spain) started on 19 September 2021 and was characterized by lava flows and a variety of explosive activity. Since lightning was frequently observed in the plume during different explosive phases, this eruption provided the rare opportunity to monitor variations in the electrical activity on various time scales continuously over several weeks.

A lightning detector was used to measure the electrical activity within the extremely low frequency range (1-45 Hz) at a sample rate of 100 Hz. The sensor was initially installed NNW (Tacande) at a distance of 2.65 km from the active vents and then relocated SW (Las Manchas) at a distance of 1.77 km, where it recorded continuously until the end of the eruption on 13 December 2021.

Throughout the eruption, an abundance of volcanic lightning was detected. Fluctuations in the electrical discharge rates were likely controlled by variations in the mass eruption rate and/or changes in the type of electrical activity produced by changes in the explosive eruption style. Comparing the ash-affected flight levels reported by Toulouse Volcanic Ash Advisory Centre to atmospheric temperature data, it can be concluded that silicate charging was the main plume electrification mechanism during the 2021 Tajogaite eruption.

Four types of electrical activity were observed, which can be linked to different explosive eruption styles as determined from thermal and visual images. Strong ash emissions, producing high volcanic ash plumes, generated hours-long periods of high-intensity volcanic lightning, while weak ash emissions only produced faint electrical discharges. Bursts of continuous low-intensity electrical discharges were detected during phases of gas jetting, Strombolian activity and lava fountaining, which only ejected relatively small amounts of ash. The duration of these bursts increases with increasing kinetic energy, height and duration of the explosion.

This study is the first to correlate electrical signatures with explosive eruption styles throughout a single eruption, which holds promise for obtaining near real-time information on the evolution of explosive volcanic activity through electrostatic monitoring in the future.