Geology of the Overhang – Greene County Parks & Trails

Indian Mound Reserve

Geology of the Overhang

Overhangs at the Indian Mound Reserve

There are several examples of overhangs at the Indian Mound Reserve, but this location, called the Large Overhang, is by far the best to observe this natural process.

Overhang Formulation — As water – which is already one of nature’s most powerful forces – flows downstream, it carries with it eroded and loosened sediments which add to it an extra grit.¹

Overhang Formulation — As a result, Massie Creek cuts away at the rock bodies on either side of the gorge. However, different rocks erode at different rates and in different ways due to their chemical makeup. Therefore, every rock layer will look a little different as it erodes.

Overhang Formulation — Massie Shale erodes very easily. You can actually break it apart between two fingers! This makes it very fragile. As a result, it erodes the most easily and rapidly of the three rock layers.

Overhang Formulation — Springfield Dolomite resists erosion much more than Massie Shale can, but is still susceptible to erosion by water as it fractures in a brick-like pattern.

Overhang Formulation — Cedarville Dolomite is the strongest against erosion of the three, especially because it does not have a specific fracture pattern.

Overhang Formulation — Because of the erosive properties of these three rock layers and their varying levels of resistance against erosion, the result is an upside-down stair-step formation.

REFERENCES

Illig, A., & Rice, T. (2020). Geologic History of the Overhang at the Indian Mound Reserve. personal.

Content developed by Audrey Illig.

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