Supereruptions are geologically instantaneous events that eject enormous amounts of magma (>1,000 km³) onto the Earth’s surface. Supereruptions have not been observed directly by modern humans, such that all our knowledge about these potentially devastating events comes from the study of past eruptions preserved in the geological record. Some supereruptions have relatively high abundances of crystals (20-40%), and the mechanisms whereby these magmas evolve in the subsurface and erupt to the surface are not very well understood. This award focused on the evolution and architecture of two magmatic systems that fed crystal-rich supereruptions: the Whakamaru group of eruptions in the Taupō Volcanic Zone, New Zealand; and the Ora Ignimbrite in northern Italy. Some of the important questions we tried to address in the study of these deposits were: How is magma organized in the shallow crust just prior to supereruptions? What are the conditions that promote accumulation of unusually high amounts of eruptible magma in the shallow crust? How do magma systems that feed supereruptions evolve to a state that leads to a supereruption? What are the timescales over which these magma bodies differentiate, stall, and erupt?

The work developed as part of this award focused primarily on the compositional characterization of volcanic glass from the two deposits. We used scanning electron microscopy-based energy-dispersive spectrometry (for major elements, in concentrations of 0.1 wt.% and above) and laser-ablation inductively coupled mass spectrometry (for trace elements, in concentrations of a few to hundreds of parts per million). We also characterized the textures of the studied rocks (i.e., the physical arrangement crystals, bubble casts, and glass) using optical and electron microscopy. This allowed us to identify different magma types that participated in the studied supereruptions.

The studies performed as part of this award provide important evidence that the shallow crust (<15 km depth), in the moments leading to supereruptions, is characterized by a complex network of laterally juxtaposed magma bodies. These magma bodies seem to persist over time, and complex eruptions are able to simultaneously tap magmas from multiple adjacent magma bodies. The studies also reveal important clues about the depths at which magma mush – the magmas from which melt-dominated magmas are extracted – appear in the crust. We also infer a complex network of different types of magma mush that coexist laterally and over time. Our results add to the growing evidence that magmatic systems encompass the whole continental crust. In the cases we studied, we find evidence for a tiered system, in which there are crustal levels in which magma is abundant, while other levels have little to no melt.

The award partly funded three PhD students at Vanderbilt University, and it also provided many opportunities for other students and postdoctoral fellows to participate in field activities in New Zealand and Italy. The project also fostered collaborations between the Vanderbilt group and colleagues at the University of Canterbury (New Zealand), and from Università Roma Tre and the Geological Survey of Bolzano (Italy). The PI offered month-long field courses in New Zealand for Vanderbilt undergraduates, which helped disseminate the findings of the project, as well as fostered an introduction to Earth Sciences, volcanology, and the methods of science to non-Earth Science students at Vanderbilt. Findings of this project have been presented in national and international scientific meetings, and they are being published as journal articles in the literature. Four complete articles have already been published or accepted for publication, and at least two others are currently in the final stages of preparation for submission.

Last Modified: 01/31/2024
Modified by: Guilherme Gualda