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John Brady Colloquium Abstract (Jan 17, 2018)

Subduction Zone Pseudomorphs: Windows on High Pressure Grain Scale Processes

News has reached geologists that mysterious changes are occurring mere kilometers beneath the Earth's surface along convergent Plate Boundaries.  Despite its proximity, at subduction travel speeds of only a few centimeters per year, a field trip down a Wadati-Benioff zone to investigate the purported activity takes too long to be practical.  So to find out what is happening, ancient rock travelers who have had time to descend and return must be identified and interrogated.  This task has been assigned to special investigators known as metamorphic petrologists.  Their approach is to question minerals, individually and in small groups, paying attention to posturing, inconsistent answers, and possible imposters. Although they can be fooled, petrologists are empowered with information from previous travelers whose trips to high pressure realms are well-documented.  And they are guided by the wisdom of their Yoda, J. Willard Gibbs.  During this lecture, details about the subduction zone experiences of several attractive but puzzling rocks found on the Greek island of Syros will be revealed.  Although most of the minerals observed have common names like calcite, quartz, muscovite, albite, epidote, and hornblende, careful investigation has implicated less well-known participants such as aragonite, phengite, clinozoisite, lawsonite, and glaucophane.  What were these minerals doing together in the Aegean subduction zone, 50 km beneath the surface and 50 million years ago?  Can a reasonable scenario be constructed from the evidence given by the Syros rocks?  Attend the lecture and join the jury.


Technical Talk: Creating an Online Petrology Textbook

I am writing an online textbook for an intermediate geoscience course on igneous and metamorphic petrology.  My goal in writing the textbook as a website is to take pedagogical advantage of the features of the Internet that we all use daily: images, sound, video, animation, access to data, and especially interactivity.  Students who read this text will be prompted to engage with the concepts and information presented through questions and responses that require exploration that includes clicking on images, changing graphs with sliders, entering data for calculations, searching for information, and more.  I have already created a number of interactive pages that clearly demonstrate the potential of the medium, providing learning tools that have not been previously available.  It is my hope that when you see what is possible the talk will evolve into a discussion of pedagogical design.  What features or incentives will encourage student readers to use the tools to learn important petrological concepts?