Field Update 2013: Examining the Magmatic Evolution of the Lassen Volcanic Center

Lassen Peak in the southern Cascades of California. The dacite from the 1915 eruption can be seen as a small tongue of black lava just below (to the right) of the main summit. Image: Erik Klemetti, July 2013. So, what have I been up to the week? It has been all about the National Science Foundation project I have going about the Lassen Volcanic Center. Last year, I had a collaborative proposal with other faculty from UC Davis, Fresno State and Sacramento State get funded by NSF and I've been collecting new samples and data this summer with one of my summer research students. My part of this proposal looks at the longterm context of the magmatic system at the Lassen Volcanic Center (LVC) by examining the zircon record from over a dozen different lavas and tephras erupted since ~620,000 years ago and as recently as 1915. So far, my students and I have tackled three of these eruptions -- the 1915 dacite of Lassen Peak (see above), the rhyodacite of Chaos Crags (from 1,100 years ago) and the 25,000-year-old dacite of Lassen Peak. Next week, we'll tackle the zircon from the rhyodacite of Eagle Peak (from ~64,000 years ago) along with the surface of some zircon from the 1915 dacite and Chaos Crags rhyodacite. Hopefully, I'll be presenting on this work at the American Geophysical Union meeting this December. Now, this past week we collected a pile of new samples to add to the collection. These samples are representative andesite to rhyolite lavas and tephras from the lifetime of the modern Lassen Volcanic Center -- chosen because these types of lava are likely to contain zircon that can be dated by methods like uranium-thorium and uranium-lead isotopic analyses. We hit quite a few places across the park, so I thought I'd show you some pictures of the lava/tephra we sampled. Rhyodacite of Sunflower Flats (~41,000 years old)