With few exceptions, Ohio is not noted for its geologic features. The face of the state is too low and too level. However, the same basic processes which shaped the spectacular scenery of the rest of the planet have also been at work in Ohio.
We should, therefore, expect to find some of the same results of those processes, although on a smaller scale. And we do. Among them are natural arches and bridges, as is the case not too far away from this location. There are gorges and rivers, as we see here.
Erosion, from various sources, has been the architect of the landscape everywhere on the planet we call home. Wind, water, and even friction has changed what we see now from what it was eons ago.
Here, at Fort Hill State Memorial, two processes were most impressive in creating the topology, and, therefore, the scenic value of the area. Glaciers gouged out depressions as their sheer mass slid across the bedrock, pushing softer soils and rock aside. What are seen as high hills and knobs were once the flat landscape of an ocean bed. That is why most knobs and foothills are the same height.
The glaciers stopped their advance as the climate worked against them. The glaciers began to melt. As they did, the gouges received the melt water. The erosion of the flowing water that collected silt and pushed along pebbles and rocks would further shape the depressions. Rain added flow to these creeks and rivers as the water would run down the sides of the resulting contours, taking with it some more abrasive sand, silt and pebbles.
As the depressions deepened, winds were funneled through them. To a minor degree, some of this action would contribute to erosive power of Nature.
As cold air collects in depressions, it can get much colder in a gorge or valley than at the top of the nearby hills. It is not uncommon for the temperature differences to be where frost and/or ice has formed in the humid conditions of the gorge, whereas, the tops of the nearby hills are comparatively balmy. This freezing and thawing loosens the rock as the water freezes and expands. The loose stone, usually rather small particles, are washed away in the melt water and rains, again adding to the erosive abilities of the water's flow.
The combination of these effects will leave harder rock exposed as the softer soils and rock are accumulated in the flow to work it's continuing effects further downstream.
Each type of rock has it's own density and resistance to these effects. Shale is quite soft. Shale will be one of the first rock strata to dislodge. Sandstone is also quite soft as it is simply compressed sand and no chemical bonding holds the particles together, yet it is considerably more dense than shale. It will erode as it is porous and is highly affected by the freezing and thawing. Also, the interlocked particles can easily be dislodged by water and the loose sand and pebbles it contains.
Limestone is a bit harder and can resist these processes more. It can actually deflect the flow by it's resistance. This rerouting of the flow and the erosive properties can make other areas erode faster, leaving a steep rock bank, or a lonesome outcropping.
As flow is directed into these channels, the erosion continues in a more concentrated area. The effect is to remove the heavier particles from some areas, leaving the more resistant rock in place to react to the more subtle forces. The ultimate result are outcropping cliffs, undercut rock overhangs, and chimney rocks.
These processes have been tirelessly reshaping this area since before humans came here, and will continue well beyond when we leave. Eventually, if Mother Nature has her way, the topology will again be level and flat. In the meantime, we can marvel at the scenery and splendor they leave for us.
Thank you for visiting. Be sure to check out the other natural formations in the area. There is quite a lot to see in a very small area.