Archbald Pothole

Useful Information

Location: 960 Scranton Carbondale Hwy, Archbald, PA 18403.
(41.512130, -75.574290)
Open: 2nd Fri APR to 3rd Sat NOV daily dawn to dusk.
Fee: free.
Classification: GeologyGlacial Mill
Light: n/a
Guided tours: self guided
Photography: allowed
Accessibility: yes
Address: Archbald Pothole State Park, U.S. Business Route 6, Archbald, PA 18403, Tel: +1-570-945-3239.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1884 discovered by coal miner Patrick Mahon while extending a mine shaft.
1887 Colonel Hackley, the landowner, built a fence and retaining wall around the hole.
1914 The widow of Colonel Hackley donates the shaft to the Lackawanna Historical Society.
1940 Lackawanna County park created.
1961 county deeds the property to the Commonwealth of Pennsylvania.
1964 Archbald Pothole State Park created.


Archbald Pothole is a natural geologic feature, a sort of erosional cave, but it was also part of the mining activities. It is a famous tourist destination since 1940, and today it is part of Archbald Pothole State Park.

During the Wisconsin Glacial Period, which ended some 10,000 BP, northeastern Pennsylvania was covered by a glacier. Melting water flowing on top of it broke through a crevasse and fell to the bedrock hundreds of metre below. At the foot of the waterfall, boulders swirl, digging deeper and deeper into the rock. Archbald Pothole was formed between 30,000 and 11,000 years ago. The result is a glacial mill or moulin, 11.5 m deep and 13 by 7 m wide at the top, 5 by 4 m wide at the bottom. It is claimed to be the largest glacier mill in the world, a dubious superlative, especially as there is another glacier mill about 300 m to the north that is said to be larger but still filled with sediment.

The natural shaft was filled with sediments, but it was discovered in 1884 by a coal miner, and subsequently used as a ventilation shaft for the mine. A large fire was kept burning at the bottom of the shaft, the hot air made the pothole function like a chimney, drawing air out of the mine. The shaft was actually discovered from underground. When the coal miner Patrick Mahon detonated a charge, a great amount of water and stones poured out. Because of the blasting, the miners kept a certain safe distance anyway, but still fled for fear of a collapse. The manager of the mining company, Edward Jones, investigated and realized that it was a large pothole. He ordered the area cleared of debris, and 800 to 1,000 tons of small rounded stones were removed.

Colonel Hackley, the landowner, built a fence and retaining wall around the hole in 1887, obviously to avoid people falling down accidentally. Edward Jones, the manager of the mining company, gave many tours of the pothole to local citizens and to noted geologists. As a result the site became a popular tourist attraction. The widow of Colonel Hackley donated the shaft to the Lackawanna Historical Society along with a piece of land of one acre in 1914. The site became a Lackawanna County park, with the addition of 150 acres of land, in 1940. The county deeded the property to the Commonwealth of Pennsylvania in 1961. Archbald Pothole State Park was finally dedicated in 1964.