Recent Sabbatical: Between January and June of 2000 I had the opportunity to travel to Chile with the principle purposes of teaching a course in advanced petrology at Universidad de Chile in Santiago and initiating a research project on Volcán Villarrica. The volcano is the most frequently active in South America, and has been continuously active - supporting a lava lake with mild strombolian activity for at least the last 17 years (note on nomenclature). The frequent activity, association with convergent plate margins, and generally mafic to intermediate chemical composition resembles other famous volcanoes such as Arenal (Costa Rica), Stromboli and Etna (Italy), albeit Villarrica is somewhat more mafic. The prominent distinguishing feature of Villarrica is the production of mafic pyroclastic flows (also see refs. 2 and 3). Two of these, the Pucón and Licán Ignimbrites, were sufficiently voluminous to have produced calderas.
Research Objectives: Mafic magmas, such as are erupted at Volcán Villarrica, are usually nearly anhydrous after they have ascended from regions of partial melting into upper crustal magma chambers, producing passive effusive-types of eruptions. Volcán Villarrica is one of a relatively few exceptions to this rule, having produced numerous explosive eruptions of basaltic andesite composition. One of the most perplexing issues regarding the origin of mafic explosive volcanism at Volcán Villarrica is the source of volatiles required to drive the eruptions. Working hypotheses may be divided into two types: 1. the eruptions occurred in response to processes external to the source magma chamber; 2. the eruptions occurred in response to processes internal to the chamber. The former requires ingestion of large amounts of meteoric water into the magma, in order to produce a catastrophic phreatomagmatic (hydrovolcanic) explosion. The latter emphasizes processes within the chamber, such as fractionation crystallization (graphical ref.) and assimilation, which may act to increase the volatile content of the magma in situ. The objective of our project has been to use oxygen isotopes as a parameter for distinguishing between these two plausible ideas.
SSAGI III Meeting : SSAGI Meetings are biannual international meetings devoted to the advancement of isotope geochemistry in South America. This year the meeting is to be held in Pucón, Chile, at the foot of Villarrica Volcano. I have teamed up with Keegan Schmidt (University of Southern California) to present an examination of the intriguing Pucón Ignimbrite.
Research Paper: Petrology and Oxygen Isotope Geochemistry of the Pucón Ignimbrite - Southern Andean Volcanic Zone, Chile: Implications for Genesis of Mafic Ignimbrites. Click on the left icon to read the summary or on the right icon to download a PDF file of the extended abstract.
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Journals of Volcán Villarrica
(JPEG photos and QuickTime Movies)
|The Geology of Volcán Villarrica and the Pucón Ignimbrite (brief overview of the geologic evolution of the volcano, emphasizing features of the Pucón Ignimbrite)|
|Ascent of Villarrica (Climb the north flank of Volcán Villarrica and view an active lava lake)|
|East Side of Volcán Villarrica (Beautiful, strange - at least to a Gringo - forests, glaciers, caldera, view of the east flank of Villarrica, and a spectacular intra-caldera ice field)|
* Nomenclature (definitions of geologic terms): Geology, like all scientific disciplines, is rife with arcane jargon. Terms highlighted in blue are linked to relevant reference pages on the web. I also recommend linking to the dictionary at the Volcano World web site.
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