[Classifieds] [classifieds] Joint seminar video linked to Clark 271 - by request.

[MBL Classifieds]

Please join us this Friday, February 21, from 3-4 p.m., for the E25-GGG joint seminar which will be v ideo linked to WHOI Clark 271- by request. 

The speaker is Leif Karlstrom , Stanford University. 

Volcanic activity at convergent plate margins is strongly localized along lineaments of active volcanoes that focus rising magma generated within the mantle below. Such volcanic fronts are dynamic structures, often migrating away from the plate boundary (the trench) over millions of years while exhibiting along-strike segmentation into discrete volcanic centers that themselves evolve in eruptive output and style. Considered as a whole, the temporal and spatial dynamics of volcanism at convergent margins reflect coupled mantle flow and melting, tectonics, surface forcing, and magma transport through a crust whose thermal and mechanical structure co-varies. I will talk about two problems in arc magmatic systems that illustrate this complexity. First I will present a new geodynamic model for arc front migration as arising from magmatic crustal thickening, constrained by observed migrations as well as isotopic data from continental and oceanic arcs. This model suggests that arc front migration reflects a mantle wedge corner flow forced away from the trench as crust thickens, with melt volumes that decrease in time as the melt column truncates. I will then talk about the time evolution of a specific volcanic center, Mount Mazama in the Oregon Cascades, which exhibited a large caldera-forming eruption at 7.8 ka after ~0.5 My of eruptive output. Patterns in the timing, spatial locations, geochemistry and volumes of small-volume eruptions in 30-40 ky preceding this climactic event suggest a growing and pressurizing magma chamber controlled the eruptive pattern at Mazama and ultimately caused the Crater Lake caldera forming eruption. 

If anyone in the Woods Hole community would like to attend via video link, please contact David Wang at dtw at whoi.edu . 



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