Dept. of Earth and Environmental Science invites you to the EES Seminar Series.

Presenter: Dr. Steven Kidder, Associate Professor, Department of  Earth & Atmospheric Science, The City College of New York

Title: The Middle Crust Under Stress: Insights from Quartz Microstructures in Experiments and Nature

Abstract: This talk reviews experimental and observational methods for reconstructing the deformation history of rocks in the middle crust, focusing on stress: how large it is, and how it varies in space and time. Stress matters because it controls how the crust deforms, from earthquakes to the slow movement of tectonic plates. At middle-crustal depths, rocks mostly respond by flowing slowly rather than breaking. As they flow, minerals like quartz often recrystallize into new grains, and the size of those grains records the stress the rock experienced. I’ll describe laboratory experiments in which quartz was squeezed and recrystallized under both constant and changing stress, and compare the results with natural rocks from active tectonic regions (New Zealand and Taiwan). Reconstructing a rock’s history also requires knowing its temperature, and I’ll show an example of how the titanium content of quartz can act as a deformation thermometer. Together, these microscopic physical and geochemical records in quartz provide useful constraints on crustal strength and improve understanding of lithospheric dynamics. 

Location: Beury Hall Room 305 (the presenter will be remote)