Observations of infrasonic volcanic jet noise: A review

Explosive volcanic eruptions are among the most powerful sources of infrasound observed on Earth and are characterized by rapid gas expansions and turbulent multiphase flow. Sustained, explosive volcanic eruptions, which can lead to tall eruptive ash columns, may be thought of as turbulent, free-shear jet flows that transition with altitude into buoyancy-driven volcanic plumes. Jet flow is also important in smaller-scale strombolian or vulcanian eruptions, which involve both violent blast-type explosions and jet flow. A wide variety of volcanic eruption phenomena have now been observed with targeted infrasound, seismo-acoustic, and multi-technology geophysical and geological field campaigns. These field studies have investigated the source mechanisms, acoustic propagation, and wavefield directivity of infrasound from volcanic eruptions. Infrasound signals from larger explosive eruptions may propagate in the atmosphere over distances of thousands of kilometers under favorable conditions, and over the past decade, infrasound technology has become increasingly integrated into volcano monitoring operations worldwide. Here I present an overview of recent observations and advances in the understanding of infrasound from volcanic eruptions. Quantitative source models for volcanic aeroacoustic infrasound can be improved through multi-disciplinary integration of field observations with numerical and laboratory experiments.