Part 2
The Bedrock Foundation
The land we call Ross County began about 420 million years ago in the bottom of an ocean, at a time when plants had just begun to colonize dry land and fishes were the most highly developed animals.
First, lime sifted down into the deep ocean. Then the sea grew shallower, and clay and silt washed in from dry land, often with organic debris. As the sea receded further about 320 million years ago, sand collected near the new seashore.
More sediment collected on top of the old. Chemical change and pressure solidified these sediments into rock - the lime into limestone, clay and silt into shale and siltstone, the sand into sandstone. As this was happenening, the earth's crust settled around an old balloon of magma in western Ohio where the crust had tried to split apart, allowing our rock layers to tilt downward to the east.
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The Greenfield Dolomite is dramatically exposed in the Rocky Fork Creek canyon in the vicinity of Seven Caves.
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Paint Creek's canyon at Rapid Forge Road also features the Greenfield Dolomite, with the waterway weaving through channels and wandering among potholes in the stone.
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The Ohio and Bedford shale forms steep slopes and is easily cut into by waterways, such as by Paint Creek here in Alum Cliffs Gorge.
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The Ohio and Bedford shale sometimes has many chemicals in it including sulphur compounds, with can also include copper - thus this exposure of the rock at "Copperas Mountain" near the Paint Valley Schools.
Copperas Mountain is the namesake of Paint Valley and Paint Creek, supposedly because Native Americans used the reddish clay residue from the shale as warpaint.
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The Waverly Sandstone is hard and strong and forms a durable cap atop the easily eroded shale below it. It usually is the top of any cliffs, such as Buzzards Roost.
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A cross-section of Ohio shows the massive deep chunks of solidified magma holding up bedrock layers in the west (left side), and how the layers have sagged downward to the east (right side), exposing ribbons of different bedrock layers east-to-west.
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A series of diagrams from a booklet on the landscape in the Hocking Hills shows the progress of our landscape from sea sediments (A and B), to a tilted and uplifted eroded land (C) that is levelled (D) and then raised again (E) and then met with glacial ice (F).
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A New Land
Then about 245 million years ago, as the age of the dinosaurs began, the young rock was raised above sea level along with the Appalachian Mountains to the east, forming new land.
Streams formed and began cutting down through the rock, seeking the ocean. Gradually the rough land was worn level, into a peneplain.
Then again it was raised up, and again erosion began. Some of the older level plain survives as the tops of our highest hills, such as the Mount Logan range and Copperas Mountain.
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Erosion works its way on the landscape in a natural progression. New land is sloping and uneven, forming rills and gulleys which widen and merge into gorges and then valleys. Eventually, all the upland is ground down into a level plain.
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A symptom of poor farming pratices is actually a sign of an early stage of landscape evolution.
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'Pine Forest Creek' in the Buzzard's Roost Nature Preserve illustrates a youthful stage of erosion.
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Small waterways merge and create larger ones, adding tributaries and power, carving out valleys and wearing down the terrain.
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Larger waterways carve their own path through a mature landscape, such as Paint Valley.
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The tips of the State Seal range of hills from Sugarloaf Mountain on the left (north), to Mount Logan on the right (south), mark an ancient level plain that erosion had ground the terrain down to - before the land rose up again and started the whole process over. These surviving high points, called "monadnocks," may also be caused by particularly hard bedrock at their location, especially since the grinding waters of the Teays River had flowed past them far longer than the Scioto's have.
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The Teays River ruled most of Ohio, flowing from the North Carolina Appalachians into Ohio and on to the sea.
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The Ancient Rivers
The waterway that ruled the our primordial landscape was the Teays River, which flowed across the nearly leveled mountains. But about 65 million years ago, as the dinosaurs' empire came to an end, the Appalachians rose up again, and streams began their work anew.
That did not stop the Teays - it just cut a gorge through the rising land, flowing from western North Carolina, actually through the mountains in the New River Gorge, down the Kanawha and Ohio valleys, up parts of the Scioto, and through Ross County. It continued westward into Indiana and Illinois to the Mississippi - or it continued northward into the Lake Erie valley and out the St. Lawrence Valley - or one and then the other after being rerouted by an early glacier. On this river floated seeds and animals from the south, some of which still survive in south-central Ohio.
But parts of the peneplains remained as tableland and the flat tops of hills. By about 2 million years ago the land had become much as we know it now - except for the its glazing by the great ice sheets.
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An ODNR map of "Bedrock Topography" shows what Ohio would look like if everything atop the underlying stone were removed - with a rainbow of colors showing the elevation of the bedrock. The Teays River Valley is clearly visible, as well as other fascinating features now long-buried.
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The Teays system brought plants northward from southern areas, some of which have weathered the vissitudes of climate change and eons of time, still remaining in Ohio... |
