Geological Survey Professional Paper 729—B Volcanic Stratigraphy of the Quaternary Rhyolite Plateau in Yellowstone National Park

Because rocks related to the second eruptive cycle of the Yellowstone region are not exposed within the national park, we do not introduce formally any of these formations in this paper other than the Mesa Falls Tuff, already defined. However, in order to emphasize the cyclic nature of Quaternary volcanic activity in the region, we make brief reference to them here. The Mesa Falls Tuff was erupted from the area of the Island Park caldera, and late collapse of that area was related to that eruption. Basaltic and rhyolitic lavas were closely associated in space and time with this volcanism. As in the first and third cycles, some associated lavas predate and others postdate the major ash flow tuff.