The Devil's Kettle waterfall is located on the Brule River, and is the most visited attraction at Judge C.R. Magney State Park near Grand Marais. That's because half the river seems to disappear, and no one can figure out where the water ends up.
If you've never been, let us explain: Just above the falls, the river splits in half. The east side (or the right side of the river in the photo above) acts like a regular waterfall. But the west side is where things get interesting – the water drops into a huge hole in the rocks.
Visitors have thrown sticks or other things down the hole to see if it would show up downstream. Nothing ever did. The DNR says some have thought the stream of water took an underground route out to Lake Superior, but that's not the case.
Hydrologists' theory is the water that enters Devil's Kettle resurfaces downstream somewhere. So they tested this last fall by measuring water flow. You can read all about the science of this here, but basically they found that the water flow above Devil's Kettle and several hundred feet below the waterfall was essentially the same.
This proves the water that enters Devil's Kettle resurges in the river below, DNR spring-shed mapping hydrologist Jeff Green said.
Exactly where the water resurges into the river isn't known, yet. This fall (when the water flow is low), they'll dump a biodegradable dye into the hole, which should show them where the Devil's Kettle stream joins back with the Brule River.
What about all those sticks?
But if the water doesn't just disappear, what happens to all those sticks people drop down the hole?
Well, they disintegrate, Calvin Alexander, who works with Green, says. The water below the kettle is "unbelievably powerful," holding the objects under water and destroying them.
The DNR says this won't happen to the dye they put down the hole, though.