Five discontinuity criteria have been proposed as tools in an effort to locate the pre-Flood/Flood boundary. On the basis of these criteria, a boundary has been proposed high in the Precambrian section for the eastern Grand Canyon and about midway in the Precambrian section of the eastern Mojave Desert. Examination of these criteria, based on certain assumptions of the pre-Flood world, suggests that changes should be considered for both the criteria and previously proposed boundaries. In general, the pre-Flood/Flood boundary is likely to occur lower in the strata—probably close to the top of the igneous/metamorphic basement.