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Cracking under pressure: Investigating ductile failure in magmatic systems

Alexcia N. Dunn 1, Patricia M. Gregg1, David Ehrhardt2, Madison L Myers3

  • Affiliations: 1Department of Earth Science & Environmental Change, University of Illinois, Urbana-Champaign, IL, USA; 2Advanced Materials Testing and Evaluation Laboratory, Department of Aerospace Engineering, University of Illinois, Urbana-Champaign, IL, USA; 3Department of Earth Sciences, Montana State University, Bozeman, MT, USA   

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 86

  • Programme No: 3.16.13

  • Theme 3 > Session 16

Abstract

A critical outstanding question in modeling dike initiation from a magma system is how failure occurs in ductile regions. To better forecast and evaluate the eruption potential of a magma system, it is necessary to understand the rheological processes that control its stability, failure, and rupture, accomplished through understanding temperature-dependent variables. In elastic materials, Young's modulus characterizes stiffness and resistance to deformation. Whereas in ductile materials, the hardening modulus describes how strength evolves beyond the yield point as the material responds to sustained stress. Constraining these mechanical properties is essential for identifying the variables governing dike initiation in ductile regions. At high strain rates, ductile material is hypothesized to behave elastically due to strain hardening, allowing cracks to initiate when stresses increase beyond a failure point. However, experimental data to understand strain hardening in ductile materials are limited. In this study, uniaxial compressive strength tests are conducted using welded ignimbrite samples from Yellowstone's Lava Creek Tuff to investigate the thermal and strain rate controls on ductile fatigue and failure. Core samples (19x39 mm, maintaining a length-to-diameter ratio of 2) of fine-grained, rhyolitic tuff are used to represent the host rock surrounding a regional magma chamber. We use a thermomechanical Instron Model 1331 at a variety of temperatures (150-750°C) to investigate the temperature dependence of the unconfined rock's hardening moduli and the failure at high temperatures. The results of this study provide key parameters for modeling magma system evolution and constraining the conditions that lead to dike initiation and eruption.