Eruption Dynamics of 21st Century Hawaiian and Strombolian Volcanism: Insights from High-Resolution Videography

Abstract

This dissertation focuses on mildly explosive eruptions–the most frequent manifestations of subaerial explosive volcanism on Earth. It uses high-speed and high-resolution cameras to record the erupted particles (pyroclasts) in-flight to measure key parameters on very fine temporal and spatial scales and link them to processes in the shallow conduit. This dissertation is composed of three projects that use data acquired at Kīlauea and Stromboli (two of the world’s most active volcanoes) to investigate what drives rapid changes in the style and intensity of weak (mild) explosive eruptions. This work begins by quantifying the frequency, duration, and steadiness (height fluctuation) of explosive events that generated a spectrum of weak activity (from Strombolian jets to Hawaiian fountains) during the 2018 fissure eruption of Kīlauea (Chapter 2). Footage of pyroclasts falling from the highest and longest fountaining phase of this eruption is then used to quantify processes of secondary fragmentation and expansion. The data show that both of these processes strongly alter the grain size of pyroclasts produced by Hawaiian fountaining eruptions (Chapter 3). On the Strombolian end of the spectrum, a detailed characterization of ejection velocity and grain size is used to interpret the observed pulsations (which occur within single explosions) in terms of the sub-second ordering of gas pockets in the shallowest levels of the conduit. My research, which aims to advance understandings of mild explosive volcanic eruptions, is driven equally by the intense public curiosity about active volcanoes and a pragmatic need to assist in improved forecasting of the likely course and footprint of all future eruptions at Stromboli and Kīlauea.