John Hora
Graduate Student
Igneous Petrology and Geochemistry
Office: 333 Weeks Hall, 1215 W. Dayton St., Madison WI 53706
Email: jhora@geology.wisc.edu
View my CV (pdf)
Research
My study focuses on the evolution of magmatic plumbing systems beneath arc volcanoes over time. Growth of arc volcanic edifices is episodic, with intervening periods of low eruptive flux and/or destruction of those edifices by gravitational collapse. Likewise, the underlying magmatic plumbing system changes over the lifetime of an arc volcano, with periodic introductions of new magma batches into the system and variable amounts of interaction among magmas populating the system during a given time period.
Linking spatial, chemical, and volume information with time allows a better understanding of how events that take place in the magmatic reservoir(s) at depth affect changes in rates of eruption at the surface. Specifically, the questions I am working toward answering are: (1) How quickly do arc volcanoes get built and how much variability in eruptive rate is there over their lifetimes? (2) What effect does crustal thickness have on those rates? (3) What is the interconnectivity of sub-volcanic magma reservoirs, and how does that change over time, especially when new magma begins recharging the system? (4) What relationships exist between times of crystallization and magma storage, chemical composition, and rates of eruption? My research entails detailed mapping, chemical and isotopic tracer analysis as well as 40Ar/39Ar and U-series geochronology, which provide quantitative timelines of eruption and crystallization, respectively.
My field site is Volcán Parinacota, in the Central Volcanic Zone of the Andes, a region of high elevations due to the extremely thick continental crust. It is an ideal site for answering the questions above since it has had a varied history involving two edifice building episodes separated by a debris avalanche which destroyed much of the early volcanic cone, and its magmatic system has been the site of episodic mafic recharge during that same time period.