Devil's Kettle Falls: the east branch (right) drops 50 feet over the rocky cliff; the west branch (left) disappears into a cauldron.
Courtesy Mark RyanWith autumn in full force and snow already in the weekend forecast there’s not much time to get out and get some last looks at some of the many interesting geological wonders we have here in Minnesota. So I thought I’d end the tourist season (at least the geo-tourist season) with one last thing that will keep you pondering all through the dreary days of winter. Hopefully, next spring, when you come out of hibernation you’ll have a solution in hand to this odd geological mystery.
Devil’s Kettle is a puzzling geological phenomenon located on the North Shore of Lake Superior. As the Brule River makes it way toward the lake, it gets split in two by a rocky knob located just above the falls. While the east half tumbles down 50 feet in normal waterfall fashion and continues toward the lake, the west half disappears in a very large pothole and is never seen again. Where does the water go? No one seems to know.
Devil's Kettle: where does all that water go?
Courtesy Mark RyanIt’s a heck of a lot of water (not to mention trees, rocks, and boulders) to just vanish into the ground. There’s been speculation that the underground river ends up somewhere along the shore of Lake Superior (about 1.5 miles away), but it has never been determined where exactly.
One theory has the river following a large fault located somewhere in the lower bedrock. But this is unlikely since it would have to be extremely large to allow for so much water to flow through it. It would also have to be precisely oriented toward the lake. And there’s never been any evidence of such a fault found in the area.
Another theory is that a lava tube formed a billion years ago when the rocks first solidified. Lava tubes can be found in Hawaii where fresh basalt is created by the islands’ volcanoes. The problem with this theory, according to geologist John C. Green, is that the rock at Devil’s Kettle waterfalls isn't basalt - it's rhyolite, and lava tubes never form in rhyolite.
But maybe it's a hidden lava tube located in a layer of basalt directly beneath the rhyolite. After all, geologists have determined that the rocks in that particular region alternate between layers of rhyolites and layers of basalts. Maybe the swirling rock-filled glacial water that formed the pothole at the end of an ice age cut down beyond the rhyolite and into an ancient lava tube. That could have happened right? Well, not likely. For one thing the basalts found in the area aren't the kind in which lava tubes would form. North Shore basalts were flood basalts that spread out on the surface like pancake batter poured onto a griddle. But even if it were the correct kind, the nearest basalt layer to Devil’s Kettle is located much too far underground to be any kind of factor in the mystery.
So where does it all that water go? Over the years, people have tried to figure it out by throwing logs, colored dyes, and even ping-pong balls into Devil’s Kettle in hopes of seeing signs of them show up along the lakeshore. But none ever has, and where it all ends up remains a mystery. (One story claims someone pushed a car into the cauldron, but to get a car to the site and be able to dump it into the kettle from above looked nearly impossible to me. When we were there, my wife remarked it’d be a great place to get rid of a body. That didn’t set well with me – and not because of the difficulty involved in doing it. I made sure she walked ahead of me on the way back.)
Anyway, if you want to go see this remarkable geological conundrum for yourself, Devil’s Kettle is located in Judge C. R. Magney State Park about fifteen miles beyond Grand Marais on Highway 61. To get to the falls you have to walk in about 1-1.5 mile from the park entrance, including climbing down (and up, on the way back) about 200 wooden steps. But the trek is well worth the effort. The park closes for the season at the end of October so if you have a chance this month you should check it out. Who knows - maybe once you see Devil’s Kettle for yourself, you’ll be the one to figure out where all that water goes.
Or maybe some of you already have a theory. If you do, let us know.
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Yellow submarine: While the Beatles' Yellow Submarine looks very funky, the actual research yellow submarine cruising about in Lake Superior is much more plain.
Courtesy Wongx ATIn a collision of Beatles and Gordon Lightfoot song topics, an unmanned, small yellow submarine is puttering about the depths of Lake Superior, providing lake quality data to researchers back on shore. Launched earlier this week, the seven-foot-long, $74,000 device is on a two-week test run to see if it can prove to be a more cost-effective way of monitoring the lake's water quality than by using people on boats.
Is the sub's color a tribute to The Beatles? Not really. Creator Jay Austin of the University of Minnesota-Duluth told the Star-Tribune: "Yellow's the international color of research. It's an easy color to see in the water, so it's very typical to paint your equipment yellow. I've got a research buoy that's the same color."
And so far into the mission's run, no sign of any Blue Meanies in the great waters of Gitchigumi.
Cold but clean: Swimmers at one of Lake Superior's north shore beaches near Duluth, Minnesota.
Courtesy Mark RyanPublic beaches along the North Shore of Lake Superior in Minnesota are the cleanest beaches of all the Great Lakes states. The National Resources Defense Council did their annual "Testing the Waters" survey and found that only 5 percent of Superior's north shore beaches in Minnesota showed worse levels of pollution than the national standards. Wisconsin had more than double the amount with 13 percent. Read more here.
Middle Falls at Gooseberry Falls State Park: Three separate lava flows form the waterfalls.
Courtesy Mark RyanRecently my wife and I took a day trip to the North Shore of Lake Superior to hike around, take pictures, and see some great geology. Scenic Highway 61 follows the lakeshore all the way into Canada, and along the way several state parks present some of the most stunning scenery and spectacular geology you’ll find in Minnesota.
In Duluth, a brisk wind made the lake a bit choppy down around the harbor entrance and small white caps rolled into the beaches of Park Point, but along the North Shore the wind subsided and the lake was placid and sparkling. It was a beautiful day, with bright sun and cool to moderate temperature, and air that was an especially clear. Across the lake, Wisconsin stood out in bold silhouette on the south shore.
Our first stop was Gooseberry Falls State Park just north of Two Harbors. One of nine state parks along the North Shore, Gooseberry is located just beyond the tunnels that cut through massive diabase ridges known as Silver Cliff and Lafayette Bluff. Diabase is an intermediate volcanic rock that due to its cooling rate, contains coarser-grained crystals than faster cooling basalt and smaller crystals than slower cooling gabbro.
Columnar jointing at Gooseberry: Polygonal jointing is evident across the top flow of the Middle Falls. The joints formed during cooling of the basalt a billion years ago.
Courtesy Mark RyanGooseberry offers easy parking and paved walking trails to view the three main waterfalls (Upper, Middle, and Lower). Despite the brisk afternoon air temperature, the waters of the Gooseberry River were warm and kids were having no problem swimming or standing under the falls. Three tiers of lava flows give the falls their structure partially due to the columnar jointing that took place when the basalt was first cooling from the outside in and shrinking into hexagonal joint structures in the process. The columnar jointing is easily viewed atop the Middle Falls. Down river the upper most flow makes up the ledges along the lakeshore.
You might wonder why so much volcanic rock is found along the North Shore. The reason’s because 1.1 billion years ago, the North America continent began to split apart in what’s called the Midcontinent Rift System. From Michigan up through the middle of Lake Superior, down Minnesota and into Kansas, the continent began to separate, releasing massive amounts of flood basalts and explosive rhyolites across the region during several eruptions. The level of volcanism was incredible, lasting for several million years. In some places along the North Shore it’s estimated that the lava flows are piled up 18 miles thick! But for reasons unknown (and lucky for us) the continental division was aborted, leaving us with interesting geology, several rugged parks, and gorgeous scenery.
Palisade Head and Shovel Point: The extrusive igneous rock, rhyolite, formed these high cliffs. Both were created from the same lava flow but the area between them has been eroded away.
Courtesy Mark RyanOur next stop was Palisade Head located within the boundaries of Tettegouche State Park. A steep road takes you to the parking area at the top of the promenade. There are a couple low walled overlooks built from local rock for viewing but you can also hike around if you want. The view is fantastic. Shovel Point, located in the park proper, can be seen sticking out over the lake to the northeast with the Sawtooth Mountains in the background. Both Palisade Head and Shovel Point were created from the same lava eruption, but one quite different from those that created Gooseberry. Whereas flood basalts created Gooseberry, an explosion of rhyolite formed Palisade Head and Shovel Point. Rhyolite is chemically similar to granite but rather than being an intrusive rock (one that cooled slowly underground) as granite is, rhyolite is extrusive, meaning it cooled relatively quickly on the surface. Evidence shows the lava flow that created both Shovel Point and Palisade Head was one of great explosive energy. As the mass of magma neared the surface pressure dropped and volatiles in its mixture (such as water) expanded its volume and punched it through a vent in the Earth’s crust in a hail of molten ash and rock. The molten material settled into a pancake-shaped mass that eventually cooled into a highly erosion-resistant rock. But the relatively rapid cooling from the outside in once again caused columnar jointing, like that seen in Gooseberry.
Face to face with North Shore geology: Palisade Head's sheer cliffs challenge local rock climbers.
Courtesy Mark RyanThe jointing and high cliffs that reach up 300 feet above the lake make Palisade Head a favorite site for rock-climbing. A group was doing just that when we were there.
Cobble beach at Sugarloaf Cove: Glaciers deposited most of the loose beach stones. Wave action shaped and sorted them.
Courtesy Mark RyanOur final stop was Sugarloaf Cove just outside the town of Schroeder. This preserve is a recent addition to the scenic North Shore. From 1943 to 1971, the cove was used by a paper company to ship rafts of pulpwood across the lake to paper mills in Ashland, Wisconsin. But today practically all traces of the business have disappeared and the 34-acre site is being preserved by the State of Minnesota and the Sugarloaf Interpretive Center Association for educational purposes. Seven acres have been designated as a State Scientific and Natural Area. A fenced area protects a native plant restoration project where volunteers planted over 12,000 native trees, plants, flowers, and grasses.
Rock sorting at Sugarloaf Cove: Lake Superior's wave action sorted beach deposits along Cobble Beach. They're all along a 50-yard stretch of the beach.
Courtesy Mark RyanThere’s a one-mile trail that takes you through a pine plantation and alder thicket and down along the lake’s rocky shoreline and to the cove. Across the cove is Sugarloaf Point, which used to be an island but is now connected to the mainland by a tombolo, a shoreline feature formed from wave action depositing sediment over a shallow area of the lakeshore. As you walk the beach toward Sugarloaf Point you’ll notice the beach deposits become increasingly larger in size, going from fine sand to large cobbles, and even an occasional boulder. Glaciers carried most of these stones from areas north and northeast, smoothing their edges in transport and depositing them here as glacial till. Lake Superior’s wave action continued rounding the stones, at the same time sorting out the sand, gravel, and cobbles by size.
Multiple lava flows at Sugarloaf Cove: Zeolites (close up in right photo) show the top of one basalt flow in contact with the bottom of another.
Courtesy Mark RyanOn the south side of Sugarloaf Point several lava flows can be seen piled one atop the other. When lava poured out on the surface a billion years ago, gases within the molten mixture formed bubbles that rose to the top of the flow much like bubbles forming on top of a pancake. As the molten material cooled into rock, these gas pockets – known as vesicles – became trapped. Additional pulses of lava soon covered the old flow and eventually everything became buried under younger sediment. At some point, hot ground water percolated through the buried masses of basalt and deposited different minerals in the vesicles in the process. These mineral deposits are known as amygdules and often appear as lighter crystals (zeolites) or agates inside the basalt layers. So when you see these lighter crystals in a rock sequence at Sugarloaf you know you’re looking at the top of a lava flow.
Lichen and cinqfoil on Sugarloaf Point: Along with wave action, several species of lichen and other plants are constantly at work eroding the North Shore basalts. The Sawtooth Mountains can be seen in the distance.
Courtesy Mark RyanVegetation on the point is very fragile, and visitors are requested not to walk out on it. At the far end of the point several lichens are working hard breaking down the basalt, along with the constant wave action of Lake Superior.
After this trip I’m anxious to go back and visit the other state parks along the North Shore. The area has so much to offer in terms of nature and geology. You can learn more by checking out some of the links below. There’s also a great book by geologist John Green titled Geology on Display that’s all about the geology of the state parks along the North Shore. If you get a chance this summer to visit these or any of the other beauty spots along Superior’s North Shore, take it - you won’t be disappointed.
LINKS
Jay Cooke State Park
Split Rock Lighthouse State Park
Crosby Manitou State Park
Temperance River State Park
Cascade State Park
Judge C. R. Magney State Park
Grand Portage State Park
More about the geological history of northeastern Minnesota
Restoration of Native Plant Communities at Sugarloaf Cove
Duluth Skyline
Courtesy Randen PedersonThis past Wednesday, May 20th at the Sky Harbor Airport in Duluth, MN the temperature rose from 46 ˚F to 86 ˚F in just 20 minutes. The temperature then reached 88 ˚F shortly there after and with in the hour came back down to 45 ˚F.
On average the difference between the high and low temperatures for that area is about 20 ˚F but Wednesday the 42 degree difference came from a shift in the winds. Earlier in the day a northeast wind was coming in off of Lake Superior cooling the bay air but at the same time, up the hill at the Duluth International Airport the temperature was a warm 88 ˚F. With a simple shift to a southwest wind, that warm air came down the hill and created what is in the process of being confirmed, the most rapid temperature change in Minnesota history.
Cargo ships carry invasive species in ballst water
Courtesy AviatorDave A recently released report warns that the Great Lakes have been invaded by foreign aquatic species resulting in ecological and environmental damage amounting to hundreds of millions of dollars.
Monitor, detect, and take required action
The findings support the need for detection and monitoring efforts at those ports believed to be at greatest risk. The report identified 30 nonnative species that pose a medium or high risk of reaching the lakes and 28 others that already have a foothold and could disperse widely.
The National Center for Environmental Assessment issued the warning in a study released (Jan 5, 09). It identified 30 nonnative species that pose a medium or high risk of reaching the lakes and 28 others that already have a foothold and could disperse widely. (click here to access report)
Flush out ship's ballast tanks with salt water
One preventive measure that works 99% of the time is to flush out the ballast tanks with salty sea water. This usually kills any foreign marine life hitch hiking a ride in the ballast tank water. Both Canada and the United States have made this a requirement for almost two decades now. Both nations also recently have ordered them to rinse empty tanks with seawater in hopes of killing organisms lurking in residual pools on the bottom.
Learn more about invasive species in the Great Lakes
- Great Lakes Facing Wide Alien Species Invasion" Discovery.com
- National Center for Environmental Assessment (EPA) report
- Great Lakes and "Invasive Species" pages on EPA website
Doomed ship: The SS Edmund Fitzgerald in quieter times.
Courtesy WikipediaThirty-three years ago today, the Great Lakes freighter SS Edmund Fitzgerald sank in a Lake Superior storm taking with it all 29 hands. 
Storm on Lake Superior: The top of the lighthouse sets about 50 feet above the lake surface at the end of the north breakwater of Duluth's canal (click on thumbnail image for a cleaner version).
Courtesy Lake Superior Marine Museum AssociationUnsecured hatches and rogue waves whipped up by the winter gale are thought to have caused the sinking.The wave sequence to the right gives a good illustration of how nasty Lake Superior can get during one of its storms.Wreckage of the Fitz was later discovered in 530 feet of water about 17 miles west of the entrance to Whitefish Bay. The disaster was immortalized in Gordon Lightfoot's song The Wreck of the Edmund Fitzgerald, and every year the Mariners' Church in Detroit, Michigan memorializes the sinking by ringing its bell 29 times, once for each life lost in the disaster.
This seems to be a big week for the Great Lakes, especially their restoration and preservation. The Great Lakes Legacy Act is making its way through Congress; presidential candidate Barack Obama has promised to set up a five billion dollar trust fund for protection of the 5 inland seas (in the spirit of non-partisan fairness here’s the Republicans’ response); the new Omnifilm, Mysteries of the Great Lakes just opened and is playing here at the SMM Omnitheater; and a new debate has started regarding the long-held practice of swabbing debris from the decks of Great Lake freighters once they get out on the lakes.
Great Lakes from space: Photo by NASAThe five Great Lakes, Superior, Michigan, Huron, Erie, and Ontario contain something like 20 percent of the world’s fresh water, and are the source of drinking water for millions of Canadians and Americans who live around them. I grew up along the shores of Lake Superior (our hillside neighborhood in Duluth set on the prehistoric lake bottom of a larger Ice Age ancestor) so I’m partial to good old Gichigami and its siblings, and I’m really glad to see some serious attention is being paid to their clean-up and preservation.
Lake Superior Day: Swimmers enjoy the waters of Lake Superior in Duluth, Minnesota's Canal Park.
Courtesy Mark RyanHow do you celebrate one of the largest pools of freshwater on Earth? By participating in the annual Lake Superior Day, that’s how! This Sunday, July 20, is Lake Superior Day, a day of celebrations for the world’s largest and cleanest freshwater lake.
Towns and communities lining the shores of Superior in Michigan, Minnesota, and Wisconsin, and the Canadian province of Ontario are planning all sorts of events in tribute to the greatest of the Great Lakes.
Picnics, beach clean-ups, library displays, kite flying, concerts, hikes, an essay contest, and government proclamations are all part of the day’s celebration to bring attention to this huge body of water that holds 10 percent of Earth’s fresh water. Events are planned all around the lake. For example, games and activities promoting water conservation will take place in Red Rock, Ontario. A family picnic is scheduled at Silver Harbour in Thunder Bay, Canada. Afternoon events will take place on Barker’s Island Festival Park in the city of Superior, Wisconsin, and scientists and lake area experts will be on hand at the Lake Superior Maritime Visitor Center at Canal Park in Duluth with information about the lake’s natural history, regional culture, and invasive aquatic species.
The annual event takes place on the third Sunday of July, and is sponsored by the Lake Superior Binational Forum, the U.S. Environmental Protection Agency, and Environment Canada. So, if you're anywhere near Gichigami this coming Sunday, join in the festivities, or just go jump in the lake!
Since 2005, an ebola-like virus has been killing fish in the Great Lakes. A major die-off was recently reported near Milwaukee, affecting some 30 species. While the disease does not affect humans, it could devastate sport and commercial fishing in the region. Though the disease has not hit Lake Superior yet, it is starting to spread out from the Great Lakes region, thanks to infected fish swimming into rivers and streams.
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