Archbald Pothole – Archbald, Pennsylvania - Atlas Obscura
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Archbald Pothole

Archbald, Pennsylvania

It would take 35 firetrucks to fill this enormous glacial pothole.  


All too often potholes can result in your car getting a busted tire or a lost hubcap. However, there is a pothole along Route 6 in Pennsylvania that could swallow your whole car and still have room for dessert.

Back in 1884, a coal miner by the name Patrick Mahon was setting off explosives to extend a mine shaft when suddenly stones and water began to flood the area. Mahon and the other workers fled the mine so as not to get killed. Once almost 1,000 tons of debris was cleared from the hole, the miners realized they discovered an enormous pothole.

The pothole is believed to have been formed around 15,000 to 20,000 years ago by whirling glacial waters combined with sand and stones. In 1884, geologist John C. Branner determined that the pothole formed as a plunge pool at the base of an incline waterfall that fell through a crack in a glacier. In 1886, another geologist by the name of Charles Ashburner hypothesized that there was no waterfall and that the pothole had been carved mainly by subglacial meltwater. 

Regardless of its formation, this glacial pothole is a geological wonder: At 38 feet deep and 42 feet by 24 feet wide at its largest diameter, it could hold up to 140,000 gallons of liquid and would take 35 firetruck tankers to fill. 

The pothole was used briefly as a ventilation shaft for the mine, acting as a chimney for a large mine fire burning under the ground. In 1887 Colonel Hackley, the landowner, constructed a retaining wall and fence around the pothole, allowing tours to be given to tourists and geologists. The land was obtained by the commonwealth of Pennsylvania in 1961, and the state formally opened Archbald Pothole State Park in 1964.

Although the Archbald Pothole is often referred to as the world’s largest glacier-formed pothole, a second pothole was discovered roughly 1,000 feet northeast of the first. Unfortunately, due to lack of funds it was never cleared out, but it is believed that the second pothole may be even larger.

Know Before You Go

The park is open daily and is located off of US Business Route 6 in Archbald, Pennsylvania. The sign can be seen clearly from the road, and there is a large viewing platform overlooking the pothole.

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