The Archbald Pothole

A Massive Pothole Created During The Last Ice Age

The Archbald Pothole was revealed in 1884 when a coal mine worker, Patrick Mahon set off explosives during a mine extension project. The explosion set off a cascade of water and stone in to the mine shaft. Patrick Mahon and the men evacuated the mine, fearing the unknown reason for the resulting chaos.

Mahon reported the incident and the mine company’s manager, Edward Jones investigated the hazard. Jones ordered the debris removed and after approximately 1000 tons of earth and stone were removed, he realized that it was a pothole of exceptional size.

The pothole was used as a ventilation shaft for the miners, as worked progressed in the coal mines.  Eventually, the mine’s owner, Colonel Hackley, built a fence around the pothole and welcomed tourists. The site attracted visitors from around the area and from neighboring states, with Edward Jones conducting most of the tours. Some attendees were well-known geologist interested in the large pothole and how it was formed.

After Colonel Hackley’s death, his widow gave one acre of land, which included the Archbald pothole, to the Lackawanna Historical Society, which in turn made it public in 1914. The historical society eventually obtained ownership of an additional 150 acres of land around the area of the pothole in 1940. All the land obtained was made into a county park until 1961 when the property and the Archbald Pothole was then given to the Commonwealth of Pennsylvania, which created a state park in 1964, appropriately called, The Archbald Pothole State Park.

Archbald Pothole measures 38 feet deep and is 42 feet wide at its maximum diameter.  At the bottom it is 17 feet by 14 feet. A geological pothole (unlike those found on our roadways) is a hole that is usually formed in the bedrock of a stream in strong rapids or at the base of a waterfall. The force of the water spins rock fragments, sand and gravel into a small indentation in the bedrock. After years and years of constant spinning, the stones and sands carve out an elliptical hole.  Archbald Pothole is an example of a pothole formed by glacial melting.

Archbald Pothole was original created the last glacier passed through the region (no one can be certain if the pothole was formed when the glacier advanced, or receded).  As the glacier melted, a stream that flowed on top may have broken through, or fallen into a crevasse and then cascaded onto the bedrock. The force of the falling water created a pothole in much the same way that a waterfall creates a pothole. The pothole was filled by falling sand, rocks and gravel. As the glacier slowly moved it created other potholes.  Archbald Pothole was preserved underground for nearly 13,000 years until its discovery by Patrick Mahon.

The Archbald Pothole State Park is located in Lackawanna County, PA.

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