Geophysics Department Seminar - Dr. Brandon Schmandt: Seismically Anisotropic Magma Reservoirs Underlying Silicic Super-Eruptions

Speaker: Dr. Brandon Schmandt; Assistant Professor, University of New Mexico Volcanic systems that produce silicic super-eruptions (>500 km3) can have catastrophic regional effects and influence global climate. Additionally, their underlying magmatic systems offer fundamental insight into production of evolved compositions in systems driven by mantle input of basaltic melts. The presentation will focus on new seismic imaging of magmatic systems underlying the 0.76 Ma Long Valley and 0.64 Ma Yellowstone calderas. Seismic tomography shows concentrated velocity anomalies in the uppermost mantle representative of continued supply of mantle melts. Mid-to-upper crustal magma reservoirs at both systems are defined by low isotropic shear velocity and strong radial anisotropy indicative of horizontal layering. Propagation of the Yellowstone hotspot’s silicic volcanism shows that the anisotropic structure diminishes with time, consistent with crystallization of compositionally evolved sill complexes. The similarity of magma reservoirs in varied tectonic settings suggests that such sill complexes may be ubiquitous features of voluminous silicic magmatic systems, and that anisotropy should be considered to seismically estimate melt content and mobility in active systems.