The importance of minerals and bubbles: (1) The internal trigger test: mapping overpressure regimes for giant magma bodies (2) Developing and incorporating instructional videos and quizzes as a blended and online learning component in an undergraduate optical microscopy curriculum.

Abstract

It is important to understand what triggers silicic eruptions because of the implications for modern-day systems. Here, we use phase equilibria modeling to determine to what extent magmas within the crust are induced to erupt due to external triggers (e.g. earthquakes; new magma injection) and to what extent they naturally evolve to a point where eruption is inevitable. Modelling the effect of fluid exsolution on the increase in system volume demonstrates that rhyolitic magmas can reach internal triggering. We find that internal triggering is effective in magmas that are stored at 10 km or shallower, revealing a window of eruptibility within the Earth’s shallow crust. Optical mineralogy is a skillset typically introduced in a microscope lab supporting lessons in Earth materials in the classroom. Challenges arise because students do not know what to look for when looking down the microscope. Eight videos were developed with accompanying pre-lab questions and hosted online as part of semester-long, undergraduate Earth materials courses at Vanderbilt University and Illinois State University. Vanderbilt students self-report increased confidence and their testing grades in 2015, when videos were implemented, were comparable or improved compared to the 2014 offering with no videos used.