The mystery of Minnesota’s disappearing river

Posted: March 18, 2016 by oldbrew in Uncategorized

Devil's Kettle at Judge C. R. Magney State Park [image credit: Chris857 / Wikipedia]

Devil’s Kettle at Judge C. R. Magney State Park [image credit: Chris857 / Wikipedia]

OK, slight exaggeration – Wikipedia says: ‘Judge C. R. Magney State Park is a state park of Minnesota, USA, on the North Shore of Lake Superior…best known for the Devil’s Kettle, an unusual waterfall and rock formation in which half of the Brule River disappears into a pothole.’
So where does it go?

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.

As geologist John C. Green writes:
‘One [theory] is that, after dropping down the pothole, the river runs along a fault underground, or as a variant, that it enters an underground channel and comes out somewhere under Lake Superior. Both of these ideas have one valid aspect in common: they recognize that water must move downhill! But the main problem is creating a channel or conduit large enough to conduct the impressive flow of half the Brule River! Faulting commonly has the effect of crushing and fracturing the rock along the fault plane. This could certainly increase the permeability of the rock — its capacity to transmit water — but the connected open spaces needed to drain half the river would be essentially impossible, especially for such a distance.

Furthermore, there is no geologic evidence for such a fault at the Devil’s Kettle. Large, continuous openings generally do not occur in rocks, except for caves in limestone terranes. The nearest limestone is probably in southeastern Minnesota, so that doesn’t help… Maybe the Devil’s Kettle bottoms out fortuitously in a great lava tube that conducts the water to the Lake… Unfortunately for this idea, they are not the right kind of volcanic rocks! Rhyolites, such as the great flow at this locality, never form lava tubes, which only develop in fluid basaltic lava. Even the basalts in this area may not be the “right kind”, being flood basalts that spread laterally as a sheet from fissures, not down the slopes of a volcano. No lava tubes have been found in the hundreds of basalt flows exposed along the North Shore. Furthermore, the nearest basalt is so far below the river bed, and even if it did contain an empty lava tube (very unlikely after its long history of deep burial) the tube would have to be both oriented in the right direction (south) and blocked above this site so that it isn’t already full of debris. And there are no reports of trees or other floating debris suddenly appearing at one spot offshore in Lake Superior. The mystery persists.’

Source: Judge C. R. Magney State Park – Wikipedia, the free encyclopedia

  1. Joe Public says:

    “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.”

    The roof of the Senate House at Cambridge University is also wholly inaccessible by road but ……

    Never underestimate the ingenuity of pranksters 😉

  2. oldbrew says:

    ‘Researchers have dropped brightly colored dyes, ping pong balls, and other objects into the Devil’s Kettle without result.’

    They could try another approach: divert the disappearing water back into the main river and see if anything dries up nearby 😉

  3. E.M.Smith says:

    We have siesmic surveys of oil and minerals all over. Can’t they do that there?

    Also, why fixate on a “channel”? A river into an aquifer would rapidly diffuse into a circular drift as Pi x diameter flow rate drop… We are not surprised by rivers that come out of mountains, draining ground water…

  4. ntesdorf says:

    It’s very good to read of a good old-fashioned mystery of Nature upon which the whole fate of Mankind does not depend.

  5. p.g.sharrow says:

    When massive lava flows over run an area, they flow along existing river or stream channels and fill them, covering the existing sand and gravel. During later erosion, springs appear along the edges and speed the local erosion. Generally the water from the old underground river channel adds to the new one’s flow. In this case the new river is adding to the lower river channel sand and gravel channel that exits in it’s buried alluvial deposits. There are many such buried streams where I live some of which were mined for the gold buried in the old sand and gravel. In one such stream that was tapped from a side drift tunnel a flow of 20 second feet was measured in the channel that came from the side and fell away into the darkness below. A Second foot of water is 480 gallons per minute. One second foot of water is a nice sized stream, 20 of them is a small river. There is no known outlet for this stream of water.

    It seems to me that the waterfall pot hole eroded through into the lower gravel bed. From time to time the gravel is over loaded and water is diverted enough to erode the secondary channel and keep it open. In time the subsurface channel will stay plugged and disappear as the water fall moves up stream…pg

  6. Power Grab says:

    I like the block-it-and-see-what-dries-up idea. 🙂

  7. Rob R says:

    From time to time rivers carry quite a lot of sediment. The hole would fill up and become blocked if it was not connected with a good sized resurgence, which could be miles away.

  8. Keith Willshaw says:

    The trouble with the techniques mentioned is that the passage time through underground aquifers can be many years. Medicine Lake in Alberta near Jasper remerges into Maligne Lake just 10 miles away but dye tracing shows that the water takes a period of time that varies from half a day to a week to travel that distance. There are disappearing rivers in Idaho which feeds into the Snake River aquifer and may not emerge for many years as the aquifiers are almost 2000 ft thick in some places.