The Mystery Behind Minnesota’s Devil’s Kettle Waterfall Has Been Solved

Minnesota’s Brule River is the source of a unique phenomenon that’s been puzzling locals, tourists, and scientists alike. Flowing not too far from the northern shore of Lake Superior, the Brule hits a divide as it travels through a cluster of volcanic rock that juts out in Judge C. R. Magney State Park. Split in two by the rocky fork, the river begins flowing both east and west. To the east, a waterfall is born, cascading half the river down into a pool, where it eventually meets up with the lake. But that western fork is a whole different story.

Unlike its eastern twin, the waterfall at the other end of this fork seemingly pours into nothingness. Called the “Devil’s Kettle,” this natural, rocky void has no obvious explanation on or below the surface. People have tried to solve the case of the bottomless waterfall by dropping ping pong balls into the pothole and casting dyes in an attempt to mark the water, but none of those plans have given anyone any clue as to where all this water is going. That is until Minnesota’s Department of Natural Resources got involved.

By measuring the water volume both above and below the Kettle, two hydrologists, Heather Emerson and Jon Libbey, found the numbers at each location were nearly identical. This finding suggests that the Devil’s Kettle waterfall likely rejoins the river underground shortly after the fork.

"What we think is happening is the water is going in the kettle, and coming up pretty close to immediately downstream of the falls," Jeff Green, a hydrologist for the Minnesota Department of Natural Resources, told Minnesota Public Radio.

The volume of water was flowing 123 cubic feet per second above the falls and 121 cubic feet per second several hundred feet downstream from the Kettle. In the fall of 2017, Green and retired University of Minnesota professor Calvin Alexander are planning to pour a biodegradable dye into the Kettle to get a more accurate reading on where and how the water meets back up with the river downstream.

So will the end of the mystery also mean the end of the Kettle’s allure? For some people, perhaps, but as Green points out, “it will still be a fascinating spot, and a beautiful spot."

Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful

Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

Big Questions
Just How Hot Is Lava?

Like the bubbling cheese of a pizza consumed too quickly, lava has been anointed as one of the most scorching substances on Earth. But just how hot is lava? How quickly could it consume your flesh and destroy everything in its path?

You may already know that lava is actually molten rock that oozes or spurts out of volcanoes because of the extreme temperatures found miles deep in the Earth. As the rocks melt, they begin to rise toward the surface. (Lava is typically referred to as magma until it reaches the surface.) As you can imagine, the heat that's needed to melt rock is pretty staggering. Cooler lava—relatively speaking—could be around 570°F, about the same as the inside of your typical pizza oven. On the extreme side, volcanoes can produce lava in excess of 2120°F, according to the United States Geological Survey.

Why is there so much variation? Different environments produce different chemical compositions and minerals that can affect temperature. Lava found in Hawaii from basalt rock, for example, tends to be on the hotter side, while minerals like the ones found near the Pacific Northwest's Mt. Saint Helens could be a few hundred degrees cooler.

After lava has erupted and its temperature begins to lower, it will eventually return to solid rock. Hotter lava flows more quickly—perhaps several feet per minute—and then slows as it cools, sometimes traveling only a couple of feet in a day.

Because moving lava takes its sweet time getting anywhere, there's not much danger. But what if you did, in some tremendously unfortunate circumstance, get exposed to lava—say, by being thrown into a lava pit like a villain in a fantasy film? First, you're unlikely to sink rapidly into it. Lava is three times as dense as water and won't simply move out of the way as quickly. You would, however, burn like a S'more at those temperatures, even if you wouldn't quite melt. It's more likely the radiant heat would singe you before you even made contact with the hypothetical lava lake, or that you'd burst into flames on contact.

Because lava is so super-heated, you might also wonder how researchers are even able to measure its temperature and answer the burning question—how hot is lava, exactly—without destroying their instrumentation. Using a meat thermometer isn't the right move, since the mercury inside would boil while the glass would shatter. Instead, volcanologists use thermocouples, or two wires joined to the same electrical source. A user can measure the resistance of the electricity at the tip and convert it to a readable temperature. Thermocouples are made from ceramic and stainless steel, and both have melting points higher than even the hottest lava. We still don't recommend using them on pizza.

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