In many of our articles we hope to give our readers a new set of eyes so as they can discover “nature” as they have never seen it before.  Most of our readers have been to Nelson Ledges State Park and are struck be amazing rock formations, but who would have thought that if you stand in the parking lot you could straddle the divide between the Lake Erie and Ohio River watershed? But you can. As you straddle the divide facing east, water on your left side would travel toward Lake Erie down to Lake Ontario; go over Niagara Falls and down the St. Lawrence River to the North Atlantic. Water on your right side would make its way to Eagle Creek, the Mahoning and Ohio Rivers, flow into the Mississippi and end up in the Gulf of Mexico.  This is an example of having “new” eyes, seeing things from a different perspective.

Sandstone formation Hocking Hills Ash Cave
Sandstone formation Hocking Hills Ash Cave

This brings us to our next topic; the geology of Ohio. We hope to give you a new perspective on the rocks and formations you see as you enjoy nearby nature. We will separate this topic into two articles: The Recipe for Rock Cake and W.I.L.M.A., Where Did All This Ice Come From? Geology is not cute, cuddly, or glamorous. But geology has a huge impact on our society. It dictates where we live, our jobs, what we grow, our mode of transportation, and the landscape we see every day. Ohio’s economic success and industrial growth are closely tied to its geology. From the vast corn and soybean farms of western Ohio to the coal mines of eastern Ohio, the limestone and salt mines and the ports of Lake Erie to the Ohio River to the south are a result of geological events. So let’s get into the kitchen by looking into the recipe file for Rock Cake. This recipe has been handed down from generation to generation dating back 1.5 billion years!

In many aspects it is very hard to imagine the drastic changes that have occurred to Ohio’s geology over the course of “geologic time”. Geologic time is defined as the period of time covering the physical formation and development of Earth, especially the period prior to human history. The history of the earth is broken up into a hierarchical set of divisions for describing geologic time. As increasingly smaller units of time, the generally accepted divisions are eon, era, period, epoch, age. Mountain ranges, glaciers, plants and animals, and vast oceans come and go in the blink of an eye relative to geologic time. I think it is easiest to think of Ohio’s geology as layers of cake. Each layer represents a defined “period” in time. If you look at the illustration in the upper right corner, you one can see layer after layer of rock formation, each layer taking millions and millions of years to lay down their material.

The second concept that is hard to fathom are the physical forces at play in shaping our geology.  The outer covering or skin of the earth is called the lithosphere consisting of the upper mantle and the crust. Volcanos erupted and land masses formed. Soon these masses began drifting and crashing into each other creating mountains ranges thousands of miles long. The term used to describe this “drift” is called plate tectonics.  It is very difficult to illustrate the energies involved when a continent crashes into another with such force that mountain ranges are formed, not to mention the abrasive power of a glacier. However, last year we all experienced a 2.5 magnitude earthquake; we have seen video of volcanic activity in Hawaii, and the force of tsunamis generated by earthquakes.

Although relatively flat today, Ohio’s geology can trace its roots to three different mountain building events as a result of the drifting land masses. The erosion that ensued, laid layer upon layer of sediment creating Ohio’s geologic features. In the early stages the western edge of the state was part of the southern extension of Precambrian Shield coming down from Canada, primarily made of granite. The eastern part of the state was part of the Grenville Mountain range that spanned 3000 miles and had peaks higher than Mt. Everest. About 1.3 billion years ago as the earth shifted a huge rift basin was created and over the next 300 million years was gradually filled in by volcanic activity and material eroding from the Grenville range. Unfathomable to think, but over time this range was reduced to rubble; however the roots of this range can still be found 13,000 feet deep as “basement rocks” under two thirds of Ohio.

East-west cross section of Ohio showing relationships of Precambrian rocks and the East Continent Rift Basin to overlying Paleozoic sedimentary rocks.
East-west cross section of Ohio showing relationships of Precambrian rocks and the East Continent
Rift Basin to overlying Paleozoic sedimentary rocks.

 Layer #1 – the Cambrian period ~ 542 million years ago. At this point in geologic time Ohio was 20 degrees south of the equator.  Ohio was covered by the Iapetus Ocean, skeletons and shells of sea creatures fell to the ocean floor thus creating limestone and dolomite. Coarse sediments washing in from erosion created sandstone 400 feet thick in parts of the southwestern Ohio.

Layer #2 – Ordovician period ~ 488 million years ago. Once again Ohio was under a shallow warm sea 100 feet deep and bordered by the new mountain range called the Taconic Mountains. Erosion of these mountains and an abundance of animal life in the sea lead to more limestone, dolomite and the initial shale deposits. Additionally, the coarse sands formed large sandstone deposits which became one of Ohio’s first oil and gas deposits.

Layer #3 – Silurian period ~ 444 million years ago. The Taconic Mountains has now been reduced to rolling hills and sedimentation was greatly reduced. Still under a vast sea, this period is known as the “age of coral”.  As a result layers of limestone and dolomite were deposited. Toward the end of the period the sea was confined to an area where the tropical sun evaporated the water and formed the huge salt deposits 2000 feet below Lake Erie.

Layer #4 – Devonian period ~ 416 million years ago. Known as the “age of fish” and still slightly south of the equator, Ohio was drying out only to be submerged again by the end of the period when the Acadian Mountains were created on the east coast from the American and European tectonic plates colliding.  As the mountains began to erode, only the fine grains of sand and sediment made their way to the ocean covering Ohio forming thick shale layers (Marcellus and Utica), limestone and huge Berea sandstone deposits. At this time in western Pennsylvania, the first significant land vegetation began to develop.  Huge trees and ferns began to cover the landscape. The West Woods, Stebbins Gulch, Penitentiary Glen, and Chapin Woods are excellent areas to see rocks from this period.

Layer #5 –Carboniferous period ~ 359 million years ago. Erosion  from the Acadia range continued and created deltas and swamps covered with lush vegetation. Sediment and sand began accumulating in the shallow sea covering southeastern part of Ohio. Yet another mountain-building event occurred, the formation of the Appalachian Mountains. Over the next several thousand years huge amounts of plant material began to accumulate. Ohio was again covered by seas and over time this material became what we know as coal.  The Sharon conglomerate found in Nelson Ledges was formed during this period as well as the substantial deposits of flint found throughout central Ohio. Around 190 million years ago, the world that we know was beginning to take shape. At this time there was one land mass called Pangaea.  As Pangaea began breaking apart into the continents we know today, the geologic activity slowed.  Volcanic activities in certain areas and the slow accumulation of sediments by erosion were the main geologic forces affecting the landscape. Then it got cold….real cold. But that is part 2 of the story.


Did you Know?

• Ohio is broken down into five Physiographic regions: Till Plains, Huron-Erie Lake Plain, Bluegrass Section, Glaciated Allegany Plateau, and Allegheny Plateau ( we live in the Glaciated Allegany Plateau)

• The western section of Ohio was home to the Great Black Swamp which stretched from Toledo area south to Lima and east to Medina.

• The Lake Erie and Ohio River watershed divide goes through Portage County.

• The state fossil is the Trilobite.

• Ohio produces 70 million tons of limestone and dolomite per year, 60 million tons of sand and gravel, 1.5 million tons of sandstone, and has a 500 year reserve of coal.

• Excluding oil and gas, over 3 billion dollars annually are generated in mineral resources.

• The Utica shale deposits under eastern Ohio hold more natural gas 38 trillion cubic feet of natural gas and 940 million barrels of oil. Marcellus shale formation reaches into eastern Ohio and holds 363 trillion cubic feet of natural gas.

• Ohio’s salt mines lay 2000 feet under Lake Erie and produce 6 million tons of salt (mostly for melting snow and ice) each year.

• The state gemstone is flint.


[toggle title_open=”Less Nearby Nature…” title_closed=”More Nearby Nature…” hide=”yes” border=”no” style=”white” excerpt_length=”0″ read_more_text=”Read More” read_less_text=”Read Less” include_excerpt_html=”no”]Eagle Creek Restoration Project, Hiram College Field Station

Saturday January 12, 2013 (10:00am-Noon)

Come to learn and see how this new preserve is being transformed from a highly impacted landscape to a habitat restoration project that involves reclamation of a section of Eagle Creek, establishment of the floodplain and important wetlands. Meet at the James H. Barrow Field Station (11305 Wheeler Rd. between Hiram and Garrettsville) at 10:00am for a brief discussion of the project and then hike to see the habitat reclamation project. Be prepared for snowy and muddy conditions. For reservations, contact Matt Sorrick at or 330.569.6003.

Beartown Lakes
Sunday, January 20 (11:00am-1:00pm)

Discover Beartown Lakes, a Geauga Park near the interesting tiny community of Taborville in Auburn Township. Join naturalist Bob Faber and hike to view three lakes, several wetlands, meadows and an old growth forest. This preserve is an easy spot for observing wildlife due to the diversity of habitats and plant species. The beech-maple forest section is a classic northeast Ohio landscape. The park is habitat for beavers, mink, muskrat and an occasional bald eagle. Hiking fee $8 for non-members, $6 for members of the Friends of the Field Station. For reservations, contact Matt Sorrick at or 330.569.6003.