Growing up in Cincinnati, I came to know its varied neighborhoods, towns, parks and suburbs but paid little attention to its topography and hydrology. Today, more than 40 years later, I recognize that this city, famous for its "Seven Hills," is draped across two broad ridges that rise along the Ohio River and merge north of the metropolitan area. The Mill Creek Valley separates these uplands, receiving tributaries from both ridges; the western flank of the west ridge drains into the Great Miami River while the east slope of the eastern ridge drops into the valley of the Little Miami River.
These three major streams and their numerous creeks expose the Ordovician bedrock of Greater Cincinnati; deposited in shallow seas about 500 million years ago, the layers of shale and limestone harbor fossils of early marine life, including trilobites and bryozoans, that lived 300 million years before dinosaurs roamed our planet. These ancient sediments remain near the surface since they overlie the Cincinnati-Kankakee Arch, a ridge of deep, Precambrian basement rock that forms the eastern rim of the Illinois Basin.
Understanding the geologic and natural history of any given region increases our appreciation of the evolutionary process and how it produced our modern landscape. We also come to recognize the impact that humans have had on that natural landscape, highlighted in Cincinnati by the industrialized and channelized Mill Creek Valley. Some disruption of nature is, of course, unavoidable, but, when we look beneath the veneer of roads, houses and buildings, we can still see nature's handiwork; it, in turn, inspires us to protect what remains of our natural heritage.
