|Spectacular Blackhand Sandstone
Spectacular Blackhand Sandstone can only be found through a small portion of southeast Ohio. It is located, in a crooked strip, from the hills around Newark through the southern part of the Hocking Hills area around Logan.
This sandstone got its name “Blackhand” from a large black handprint that was sketched on a sandstone cliff that overlooked the Licking River near Newark.
It was believed that the handprint was drawn by prehistoric Indians showing the direction to flint deposits at an area now known as Flint Ridge. The remains of this cliff can still be seen at the Blackhand Gorge State Nature Preserve.
Blackhand Sandstone was formed over 300 million years ago when most of Ohio was covered by a shallow sea. Sand was eroded from distant mountains and floated down the streams into Ohio’s sea where it collected in a long, narrow delta.
Then, the currents changed, and for a while the sands were deposited into the delta at an angle. This created what is called cross-bedding. When the currents returned to normal, the sand was once again deposited in the delta in flat, horizontal layers.
Fine sand and silt was deposited over top of the heavy sands and buried it. The heavy weight of this covering compressed the heavy sands. As groundwater, with iron oxide in it, seeped through the layers of heavy sands the iron cemented the sands grains into solid rock. This rock was as thin as 80 feet thick, but in some places it was 250 feet thick!
The same waters that helped form the Blackhand Sandstone, also eroded it over time. The groundwater slowly washed away the cement holding the particles of sand together and eventually began washing away the sand itself.
As the water worked its way into the joints and crevices of the sandstone, it easily cut through layers of rock. Since the middle layer of the sandstone was cross-bedded, and not as tightly cemented, it was eroded much faster, leaving the upper and lower layers in place.
These upper and lower layers of Blackhand Sandstone form the ceilings and floors of recess caves and rock shelters, which are found in areas where this sandstone is located. The largest recess cave in Ohio is Ash Cave in Hocking Hills State Park.
The vertical surfaces of Blackhand Sandstone continue to be eroded by wind and water. Interesting formations can be found on these surfaces where there is softer rock mixed with the harder rock. One formation is called honeycomb, which looks like a very large honeycomb in a bees hive.
Another formation is called concretion, which occurs when a large amount of the cementing agent, most times iron oxide, is highly concentrated turning the sandstone a dark brown-red color.
Slump blocks are also common in areas where there are outcrops of Blackhand Sandstone. Slump blocks occur when a joint is eroded to the point that the chunk of rock can no longer be held to the surface of the rock face and it falls away.
Blackhand Sandstone sure is spectacular, don’t you think?
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