Layering in Yellowstone Rhyolite
The layered structure of much of the rhyolite of Yellowstone National Park consists of either a wavy lamination or a coarse stratification. Iddings attributed the layering to spreading of heterogeneous lava. Evidence is herein presented in favor of that hypothesis. Brouwer has suggested that the development of some of the coarser stratification was influenced by crystallization along planes developed by shear when the lava was in a highly viscous state and no longer able to spread. The writer suggests an additional possibility-that the crystallization of some of the layers may have been induced by vapors not originally included within the lava, but which invaded pervious bands originally determined by flowage.