Rocks can become pocked with pits over time.

Dear Naturalist,

Why are there pot-hole type formations in the rock along the Flat Rock Trail on the Blue Ridge Parkway? — SJ, Boone


Those pits are the result of a positive feedback loop — a process in which an interaction between two things produces an effect that amplifies change overtime. The entire natural world is composed of millions of positive and negative loops intertwined.

For example, a simple positive loop is that between a plant and soil. As plants die and decompose they, themselves, produce soil. The deeper the soil, the more plants can grow. When more plants grow, more plants die and more soil is produced.

Positive loops are not always positive, however. They can be downright harmful. One such relationship is between careless hikers and erosion.

When faced with a muddy or eroded trail, a careless hiker might choose to avoid uneven footing and, instead, walk on the edge of the trail or through the vegetation alongside the trail. Overtime, this leads to more erosion, more environmental degradation and, possibly, even more people choosing to hike further off the trail.

Places that were once abundant with life can erode away in just a few weeks in our most fragile habitat, like that atop Grandfather Mountain.

Flat Rock’s weathering pits are also the result of a feedback loop that involves erosion. In a weathering pit, the depression itself traps water. The water, in turn, chemically dissolves the rock making the depression deeper and deeper. The deeper the weathering pit, the longer the water remains trapped in the pit. And the cycle continues for millenia.

The grains of sand that are dissolved from the rock by the water are occasionally removed from the pit by wind or heavy rain.

And so the pits get deeper, bigger and even more fun to sit in each time you visit Flat Rock. Did I mention that you should stay on the trail on your way there?

If you have a question concerning flora and fauna, please email All of your questions will be answered. One or two will be featured next week. See you on the trails!

Amy Renfranz is the Chief Naturalist for the Grandfather Mountain Stewardship Foundation. She is a Certified Naturalist through the Yellowstone Institute and a Certified Environmental Educator in the state of North Carolina.

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