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Why Cincinnati Rocks?

March 21, 2022
A child holds a A rock with the traces of ancient marine life fossilized within it
A rock with the traces of ancient marine life fossilized within it

by Bob Buring, Naturalist

Our wonderful town is famous both nationally and worldwide for a multitude of reasons. Most people do not realize our rocks also put us on the map. Why?

Under our feet, past a little soil, are timeless and deep layers of rock, averaging one mile in depth. They are known as sedimentary rocks, originating as deposits on a shallow sea floor many millions of years ago when the climate was warm and mild. These sediments were comprised of both living and non-living things. The enormous pressure of overlying, younger layers squeezed out the water, forming rock. Of these, some are also cemented by the chemicals within ancient marine animals.

Planetary scientists, over many years, have studied these many levels of rock and fossils to reconstruct the physical and biological history of our world.

How do our local rocks stand out in this global crowd? It begins with the dance of the continents.

A child holds a A rock with the traces of ancient marine life fossilized within it
A rock with the traces of ancient marine life fossilized within it

To start, our planet and solar system are 4.6 billion years old. Initially the earth was very hot, with diffuse volcanic activity and bombardment by extraplanetary bodies. This was the “Hadean” eon, lasting about 600 million years. When the earth finally cooled, land masses formed – our continents.

Due to forces beneath, these solid pieces of earth have been slowing moving. Beginning about 3.1 billion years ago, they occasionally collided with one another. When enough of these behemoths came together, they formed a “supercontinent”. Of the eleven that have existed, “Pangaea” is the most famous.

One of the most important results of colliding land masses is mountain-building, or “orogeny”. As two massive objects meet, there is nowhere to go but “up”, and a mountain range is created.

While the early mountains to our east were formed in this manner, our immediate region was thrust upward, eroding the younger, overlying layers and exposing more ancient rocks below. These older sedimentary rocks in Cincinnati, in a narrow region thirty to fifty miles east and west of our town, were the first of their age studied by geologists and are named for the region.

Virtually nowhere else in the world are our 450,000,000 year-old “Ordovician” rocks exposed at the surface, so geologists named these layers the “Cincinnatian Series.”

As a result, we have a rock-solid spot on the map of planetary history – and the dance continues………...