Compression in Multiple Regimes: Studies of Plagioclase, Cu, and MgO 
Melissa Sims wearing a blue shirt and glasses

Dr. Melissa Sims, Postdoc
Johns Hopkins – Earth and Planetary Sciences

Wednesday, May 12th, 2021
1pm – via zoom

Geoscience problems, from meteorite impacts to exoplanet interiors, require study of timescales that span orders of magnitude.  However, the shock and static experiments required to examine these processes occur over limited timescales, strain-rates, and temperatures compared to natural systems. The effects of kinetics and strain-rate are relatively unconstrained. It is therefore important to understand their effects during the experiments used to determine phase diagrams and equation of state models.  In meteoritic systems, understanding kinetic and strain-rate effects is vital due to the millisecond timescales of impact processes. Temperature, kinetics and strain-rate studies are important to the analysis of exoplanets because rheological properties, such as viscosity, are dependent on phase identities and deformation mechanisms. In this presentation, I will discuss high pressure deformation and phase relations in plagioclase, copper, and MgO across compression regimes. In plagioclase, I examine the effects of compression-rate and kinetics on deformation, transition mechanisms, and subsequent phase formation using laser heated membrane driven compression. In copper, we compare computational work to laser shock experiments and examine textural changes across the fcc to bcc phase transition. In MgO, we study the effect of temperature on the B1-B2 transition. We compare our ramp experiments to shock data collected along the Hugoniot. These studies allow us to more accurately examine geological events with timescales from microseconds to billions of years.