Diverse Eruptive Activity Revealed by Acoustic and Electromagnetic Observations of the 14 July 2013 Intense Vulcanian Eruption of Tungurahua Volcano, Ecuador

During the powerful July 2013 eruption of Tungurahua volcano, Ecuador, we recorded exceptionally high amplitude, long-period infrasound (1,600-Pa peak-to-peak amplitude, 5.5-s period) on sensors within 2 km of the vent alongside electromagnetic signals from volcanic lightning serendipitously captured as interference. This explosion was one of Tungurahua's most powerful vulcanian eruptions since recent activity began in 1999, and its acoustic wave is among the most powerful volcanic infrasound ever recorded anywhere. We use these data to quantify erupted volume from the main explosion and to classify postexplosive degassing into distinct emission styles. Additionally, we demonstrate a highly effective method of recording lightning-related electromagnetic signals alongside infrasound. Detailed chronologies of powerful vulcanian eruptions are rare; this study demonstrates that diverse eruptive processes can occur in such eruptions and that near-vent infrasound and electromagnetic data can elucidate them. Plain Language Summary Vulcanian-type volcanic eruptions begin when pressurized gas in the vent is abruptly released in a powerful explosion. We recorded pressure waves produced in a powerful vulcanian-type eruption at Volcan Tungurahua (Ecuador) on 14 July 2013. The wave from the main explosion shows that the vent ruptured in a complex 2-s process including uplift followed by multiple distinct bursts, releasing an immense quantity of gas. This was among the most powerful pressure waves ever recorded from a vulcanian-type eruption. Subsequent waves show that the volcano continued to emit gas and ash after the main explosion; this emission occurred in three distinct types. Additionally, volcanic lightning was recorded serendipitously as interference in the acoustic data. Frequent lightning began abruptly 25 s after the eruption onset and became more sporadic 4 min later, finally ceasing 20 min after the explosion. This work shows that explosions and emissions in vulcanian eruptions can be complex and that acoustic recordings near the vent can elucidate these processes, strengthening volcano monitoring, and science.