John Lyons – Research Geophysicist from the USGS Alaska Volcano Observatory
Title: Fire and ice (water): What infrasound reveals about recent volcanic eruptions in Alaska and Hawaii
Abstract: Erupting volcanoes produce low-frequency sound (or infrasound) when they disturb the atmosphere, and volcanologists use those signals to monitor and study volcanic activity. Improvements in instrumentation and data processing are leading to more infrasound recordings of increasingly diverse volcanic activity across the world, with some surprising and exciting discoveries about how volcanoes generate infrasound. Here, we’ll explore the infrasound from two very different recent eruptions in Alaska and Hawaii, and show how infrasound is capable of revealing unique details of the eruption mechanics that would have otherwise escaped detection.
Bogoslof volcano is a remote, back-arc volcano in the Aleutian Islands of Alaska with a shallowly (<100 m) submerged vent that produced more than 70 explosive eruptions from December 2016 to August 2017. The eruptions produced abundant infrasound recorded from 60 to 850 km from the volcano, and these data are the first from a shallowly submarine, explosive eruption. We model the distinct low-frequency infrasound signals as the nonlinear oscillation and rupture of explosion generated gas bubbles at the water-air interface, and constrain the size of the bubbles (spoiler: they were giant). In Hawaii, the 2018 eruption of Kilauea volcano was one of the most significant and destructive eruptions there in several centuries. The Lower East Rift Zone portion of the eruption was focused at Fissure 8 for nearly two months, providing an unprecedented opportunity to observe and characterize activity at the vent and along the 300 m spillway that drained the lava pond around the vent. The vent + spillway was a dynamic area, with many features capable of sound production, including standing waves, pulsing spillway outflow, shooting flow, and variable gas emissions; many of these sources are similar to the processes that generate fluvial infrasound. We investigate the characteristics of the infrasound and compare them with time-lapse photography, thermal imagery, and unoccupied aircraft systems (UAS) footage in order to elucidate the nature of the sources of the vent and spillway infrasound.
Where: RUCH 103
When: Monday, October 21st