Eoghan P. Holohan, Valentin R. Troll, Benjamin van Wyk de Vries, John J. Walsh, Thomas R. Walter; Unzipping Long Valley: An explanation for vent migration patterns during an elliptical ring fracture eruption. Geology 2008; 36 (4): 323-326. doi: 10.1130/G24329A.1
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Long Valley caldera, California, formed during the cataclysmic Pleistocene eruption of the Bishop Tuff. Previous stratigraphic and petrologic studies of this eruption deciphered an intriguing pattern of vent migration, thought to mirror the lateral propagation (“unzipping”) of magma-tapping ring fractures during caldera collapse. From scaled analog models, we show that this unzipping pattern was intrinsically related to the high plan-view ellipticity of the precollapse magma chamber roof. We also provide a first-order kinematic explanation for the systematic location of initial elliptical roof failure and for the lateral propagation of highly elliptical ring fractures.