Judge C. R. Magney State Park is a state park of Minnesota, USA, on the North Shore of Lake Superior. The park is best known for “The Devil’s Kettle”, an unusual waterfall located on the Brule River 1.5 miles (2.4 km) from its mouth. The river splits in two to flow around a mass of rhyolite rock. The eastern flow goes over a two-step, 50-foot (15 m) waterfall and continues downstream. The western flow surges into a pothole, falling at least 10 feet (3.0 m), and disappears underground. It is believed the water rejoins the main channel of the river or has a separate outlet into Lake Superior, but it has never been located. Researchers have dropped brightly colored dyes, ping pong balls, and other objects into the Devil’s Kettle without result. There is even a legend that someone pushed a car into the fissure, but given that the Devil’s Kettle is wholly inaccessible by road, most commentators dismiss this as hyperbole.
Not only is the outlet unknown, but there is currently no satisfactory geological explanation for the Devil’s Kettle. Certainly riverbed potholes are known to form from rocks and grit swirling in an eddy with such force that they eventually drill a vertical shaft in the bedrock. How the flow is conducted away laterally, however, remains enigmatic.