Electronic Theses and Dissertations Archive

Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Earth Sciences

Committee Chair

Eunseo Choi

Committee Member

Christodoulos Kyriakopoulos

Committee Member

Mitchell Withers

Committee Member

Randel Cox

Committee Member

Robert Smalley Jr.

Abstract

Continental rift evolution emerges from the dynamic interaction among far-field tectonic forces, mantle processes, and lithospheric rheology. Variations in plate-scale stress transmission and thermomechanical perturbations associated with mantle upwelling exert first-order control on strain localization, crustal thinning, and the transition toward continental breakup or rift failure. Allowing plate motion to emerge from internal force balance, rather than prescribing kinematic boundary conditions, provides a physically consistent framework for investigating these interactions. Time-dependent changes in far-field driving stresses and mantle plume activity can modify the mechanical state of the lithosphere and extension velocities, influencing whether a rift matures into a plate boundary or becomes a failed system. First, we investigate the effects of temporally varying driving forces on rift evolution using the open-source mantle convection code ASPECT. Far-field stresses decreasing over time, potentially associated with variations in slab dynamics, are implemented through time-dependent boundary tractions. Results show that later initiation of traction reduction and slower force decay promote sustained extension and increase the likelihood of continental breakup. A traction reduction of 25\% can still lead to breakup under favorable conditions, whereas greater reductions of 50–75\% produce stalled or failed rift systems. The models exhibit non-monotonic evolution of extension velocity ($V_E$), including transient increases during periods of decreasing driving force. Semi-analytic models confirm that this behavior results from dynamically evolving force balance, indicating that rifts may accelerate toward breakup even when present-day extension rates are low. Second, we examine the role of mantle plume forcing in rifts driven by diminishing far-field tractions. Time-dependent thermal boundary conditions simulate plume arrival, persistence, and decay. Varying the magnitude and duration of thermal anomalies produces both plume-assisted breakup and plume-modulated rift failure. Models reproduce multiple subsidence and uplift episodes reflecting thermal weakening and conductive cooling. Reducing far-field traction by 40 MPa results in rapid breakup (50–60 Ma), whereas larger reductions (120 MPa) sustain long-lived rifting ($\sim$150 Ma). Short-lived thermal perturbations (15–20 Ma) lead to rift termination, while prolonged forcing ($\ge$25 Ma) promotes sustained deformation and breakup.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest/Clarivate.

Notes

Open Access.

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