A Multidisciplinary Study on the Crustal Nature of Volcanic Conduits and Magma Reservoirs

Abstract

Volcanic settings vary widely not only in their eruptive style and products, but in the manner magma travels from deep sources to individual eruptive centers. Imaging these pathways, and their associated crustal reservoirs, provides unique and unprecedented views into these environments. Imaging techniques are varied with the strength of the technique often based on data availability. As such, we focus on two methods—gravity and seismic—in two different settings, each with its own unique volcanic environments, crustal structures, and associated data resources. The first, the Hawaiian Islands, are the most geologically studied hot-spot islands in the world, yet the only large- scale compilation of marine and land gravity data is more than 45 years old. We present a new chain-wide gravity compilation allowing us to locate current and former volcanic centers, major rift zones, a previously suggested volcano, and show that volcanoes along the chain are composed of a small proportion of intrusive material (< 30% by volume). At the second area, the arc-volcanism of southern Washington, we used ambient seismic noise methods to constrain the crustal pathways of deep-sourced melt to the surface. We image two zones of reduced velocity, one of which correlates with a proposed extensive zone of mid-crustal partial melt which likely supplies evolved magmas to the surrounding volcanoes and vents, including Mounts St. Helens and Adams.