Date of Award

May 2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology

First Advisor

William Gosnold

Abstract

Using the spatiotemporal record of the 2.1–0 Ma ignimbrite flare-up of the Yellowstone Plateau Volcanic Field (YPVF) as a proxy for batholith formation at depth, this dissertation develops and applies the Finite Difference Heat Flow Simulation (FDHFS) program to model crustal thermal evolution beneath the supervolcano. FDHFS, a modular C++ numerical simulator, solves the transient heat equation incorporating variable thermal conductivity, radiogenic heat production, and directional advection in three-dimensional Cartesian grids. Validation against analytical benchmarks and seafloor-spreading analogs confirms its fidelity for combined conduction-advection processes in heterogeneous crustal settings.

High-resolution volume–time analysis of major ignimbrite pulses (Huckleberry Ridge, Mesa Falls, and Lava Creek Tuffs) reveals episodic extrusion rates (0.003–0.0245 km³ yr⁻¹) up to an order of magnitude higher than the long-term average (0.002 km³ yr⁻¹). Inversion using 3:1 to 5:1 plutonic:volcanic ratios yields peak intrusion rates of 0.009–0.1225 km³ yr⁻¹, documenting the incremental assembly of an estimated 12,990–21,650 km³ of granitic material in the upper crust (5–17 km depth).

Two-dimensional FDHFS simulations illustrate how sustained plume-driven heat input elevates geotherms, crosses the rhyolite solidus at shallow depths, and shallows the brittle–ductile transition through progressive crustal weakening. These results establish a positive thermomechanical feedback between mantle power input, temperature elevation, mechanical failure, and the accumulation of larger rhyolitic magma bodies. The nested caldera architecture further records composite pluton construction over multi-million-year timescales.

Collectively, the findings reinforce the generality of episodic, thermally modulated batholith construction across tectonic settings and provide a robust framework for interpreting active magmatic systems, volcanic hazards, and geothermal resources.

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