In northern Minnesota, the Bruehl River comes to a forked waterfall. One side is well behaved, goes over the edge and then flows downwards to Lake Superior. The other side goes into a big hole at which point... Half of this river flows into this massive hole at which point it is never seen again. All we know is that half of the Bruehl River disappears into the Devil's Kettle. People have tried to figure this out. Scientists have dumped, dies, hundreds of ping-pong balls, GPS trackers. They've even just shoved logs into this hole. The expectation is that it would come up somewhere in Lake Superior. But none of the things people have tried to track the flow of this water have worked. They simply disappear. What is especially frustrating and confusing for geologists is that this really shouldn't be happening. Geologically speaking, northern Minnesota is full of holes. Sometimes called kettles or cauldrons, these are places where harder rocks get trapped in a softer depression. They swirl around around around and they sort of carve these deep potholes. These can be big. They can be 30 feet deep, plenty large enough to suck an unsuspecting swimmer to their demise. But what they don't do is turn into miles of underground tunnel. If all of this were happening in say limestone, it would make perfect sense. The water would have eroded a passageway and created its own kind of tunnel. But this isn't limestone. It's a much harder rock called rialite. And rialite doesn't form tunnels, at least not naturally. So there's only a few explanations. One possibility is that maybe there's a fault line there. But this isn't a trickle of water. It's half a river's worth of water. A fault line would have to be enormous to accommodate that level of water. And there's no evidence for a fault line anywhere near there. There's a second theory. Maybe the kettle has drilled far enough down that it had a lucky encounter with a lava tube left there for millions of years before. But there's a small problem. Rialite doesn't make lava tubes. And even the basalt, which is far, far below, it wasn't the right kind of lava flow to create such a tunnel. In a lot of ways, we know the answer. The river isn't defying physics. You know, it's flowing downhill and almost certainly ending up in like superior. The thing that has everyone frustrated and confused is how and the harder that scientists and geologists try to solve this mystery and then fail the more mysterious devil's kettle becomes. Where's that water going? Where's it going? Subscribe here and watch more videos here. This is really what this wasn't worth.