PoreLab Lecture this Wednesday at 15:00 (Central Europe) on Zoom. To join, please follow the link below the abstract or add this event to your calendar by opening the attached calendar ics-file.
When: Wednesday 24 February at 15:00 (Oslo time)
Where: online (see below)
Title: Healing of crystal-rich granular materials in volcanic environments by solid-state sintering:
implications for fluid flow, deformation and explosivity
Speaker: Dr. Amy Ryan
Affiliation: Postdoctoral associate, Rock and Mineral Physics Laboratory, University of Minnesota
In volcanic systems, the volume and pressure state of magmatic gases control eruptive behavior. Where gases can vent out of a volcano, eruptions can be quiescent. However, where outgassing is suppressed, explosivity is likely. At the elevated pressure-temperature conditions endemic to volcanic environments, permeable pathways that allow gas transmission are ephemeral and can be destroyed by densification processes. Predictions of the intensity and timing of explosive eruptions depend on an understanding of the mechanisms that create and destroy permeable pathways, and their operational timescales. Solid-state sintering is a diffusion-driven process that converts unconsolidated, crystalline aggregates into dense, low-permeability composites. Elevated temperatures and pressures and substantial dwell times facilitate densification and lithification by solid-state sintering. However, solid-state sintering has largely been discounted in volcanic systems because its operational timescales were assumed to be long.
In this talk I will present results from field and experimental studies that support solid-state sintering occurring in volcanic settings on timescales short enough to influence eruptive activity. I will introduce a quantitative model, developed from experimental results, that predicts the time-dependent evolution of material density as a result of solid-state sintering, and will show how it can be applied to determine timescales of porosity and permeability reduction in various volcanic environments. Finally, I will discuss how simultaneous densification and lithification can hinder fluid flow and modulate eruptive behavior, including promoting cyclical explosivity.
Attached figure (pdf): The experimental starting material (a crystal-rich rock powder; left) and a representative product of hot-pressing experiments – a competent rock core (center) that show microscopic evidence of solid-state sintering (right), including the formation of patches of coalesced particles and “necks” of crystalline materials that now join grains.
Join by H.323:
Meeting ID: 673 5647 1922