If you have ever worried that we have solved all the mysteries of nature, fear not. Minnesota’s Devil’s Kettle Falls has been perplexing hikers and geologists for generations. The Devil's Kettle is a mystifying geological wonder situated inside Judge C. R. Magney State Park in Minnesota, in USA, just off the North Shore of Lake Superior. The Brule River makes its way through the park; it drops 800 feet in elevation and makes plentiful waterfalls in the process.
One of these waterfalls is quite distinct. Approximately 2.4 km before the river empties into Lake Superior; it gets split in two by a rocky outcrop. The eastern part drops 50 feet below and continues towards Lake Superior. The western part falls 10 feet into a massive pothole, which is called the “Devil's Kettle” and disappears. No one knows where the water goes. It is thought there must be an exit point somewhere underneath Lake Superior, but it has never been located. From the last several years, investigators have dropped brightly colored dyes, ping pong balls, and many other things into the Devil's Kettle.
Surprisingly none of them have ever been found. One philosophy is that the river flows along a subversive fault and comes out somewhere under Lake Superior. This is dubious, because for this to happen, the fault would have to be exactly oriented towards the lake, and would have to be big enough to let the flow of half the river. Even if such a fault is real, it would have probably been clogged over the years as rocks, sand, logs and other materials fell into the kettle. Besides, there is no sign of such a fault in the area. One more theory is found when millions of years ago a lava tube formed when the rocks first solidified.
The issue with this theory is that the rock at Devil’s Kettle waterfalls is rhyolite, and lava tubes never form in rhyolite. Lava tubes form in basalt flowing down the slopes of volcanoes, and the adjacent basalt layer to Devil’s Kettle is situated much too far underground to be any kind of factor in the mystery. The existence of a big underground cave is also ruled out because underground caves form in limestone rock, and there is no limestone in the area. The mystery is compounded by the fact no floating debris suddenly appearing at one spot offshore in Lake Superior has ever been reported.