Literally dig deeper into the earth surface and discover what is lying right under your feet.
A photograph captured by the Mars rover, Curiosity, shows an unconformity in the strata of Mount Sharp, a mountain inside nearby Gale Crater. An unconformity is a geological feature marking a stop in sedimentation and erosion of a surface before the overlying layer is deposited. The photo above shows the two distinct rock layers (marked by a line of white dots) that make up the unconformity. The upper layer, which is tilted left to right in relation to the lower layer, contains no evidence of hydrated minerals found in the lower layer. This idicates the two layers were laid down in different environments.
Check out some amazing footage of mud and debris flowing from nearby mountains during a heavy rainfall in the village of Virgen, Austria. What's cool is that the flows come in pulses, which I guess is typical of this kind of thing there.
Courtesy NASA via UStreamThe Mars rover Curiosity managed to make it through seven minutes of terror and land safely and pretty much flawlessly this morning on the surface of the Red Planet. The amazingly complicated landing, which took place around 12:25 CDT, was broadcast on the internet and on NASA-TV. It was very thrilling to watch, and a great accomplishment for all the scientists involved. They were ecstatic, as you can well imagine.
Courtesy Mark RyanA special group of rock hounds gathered over the weekend in the Twin Cities to celebrate and give praise to agates, those special gemstones found in just about every country of the world. “A Celebration of Agates” was held July 26-29, 2012 at the Lindbergh Center at Hopkins High School in Minnetonka, MN.
Courtesy Mark RyanThe weekend event was hosted by the Minnesota Mineral Club and included presentations, book signings, banquets, plenty of vendors, and lots of agates – piles of them, on tables, in buckets, inside display cases, all there for the public to enjoy.
Each year at the Minnesota State Fair, I man a booth for the Geological Society of Minnesota. It’s great talking geology with visitors, answering their rock and geology questions. But by far the most frequent questions and discussions are about agates - specifically, those found in the Lake Superior region. It’s not surprising that the Lake Superior agate is Minnesota's state gem.
Courtesy Mark RyanThese beautiful gemstones formed inside the empty spaces (vesicles) created by gas bubbles trapped in lava flows that poured out during the Mid-continental Rift (MCR) episode about a billion years ago and cooled into fine-grained basalts. Later, when the basalts were buried deep under sediments, ground water or hydrothermal activity flowing through the sequence deposited minerals (mainly silicon dioxide) inside the empty spaces layer by layer - and from the inside out - forming amygdules. Trace minerals and impurities can add color to each layer, creating bands of different color. In the Lake Superior area, the rocks became exposed again, and the basalts began to weather leaving the harder amygdules to fall out. Glaciers transported agates from the Lake Superior region and deposited them with tons of other rocks forming gravel pits to the south of the lake. Some of the best Lake Superior agates can be found around the Twin Cities.
Courtesy Mark RyanPersonally, I never got into collecting them, I’ve always been mostly into fossils, but I have to admit, some of those agates I saw at the show were stunningly beautiful pieces of natural art. There’s something very attractive about a collection of Lake Superior agates covering a tabletop or laid out inside a display case. But Minnesota’s state rock wasn’t the only agate on display. Participants from many states and several countries including India, Australia, Germany, and South America brought their collections and knowledge to share with other agate lovers.
Courtesy Mark RyanI usually don’t buy rocks, fossils or minerals – I like to find my own – but after I watched one vendor use some sort of strange bolt-cutting tool to break open several large geodes visitors had selected, I had to try my own hand at it.
Buckets of geodes lined a nearby table. The largest were as big as a softball but picked out a modest, three-inch diameter "Mexican Coconut” mined in Chihuahua, Mexico.
Courtesy Mark RyanThese geodes formed in a similar manner as most agates: a hollow space left by gas bubbles in a cooling lava flow allowed for minerals to line the interior and crystals to grow as groundwater flows through it. Sometimes agate (chalcedony i.e. silicon dioxide) forms inside, other times it can be any number of iron-oxides, silicates (quartz), or calcite. The “Coconut” geodes formed in a 44 million year old ash-flow tuff that over time eroded into whitish clay. The geodes are mined from the clay 200 feet below the surface. Geode is a general term for a rock with a hollow space inside. Sometimes geodes can contain agate material such as chalcedony or jasper, and sometimes agates can be considered geodes (if they have a hollow space), but the two terms aren’t always interchangeable.
According to the very helpful vendor, the trick to picking the most primo geode was to find one the feels lighter than others of comparable size. It would logically follow that it has a larger hollow space and therefore possibly more crystal growth inside.
Courtesy Mark RyanSo, I picked out a good one, and the vendor took it and tightened what looked like a large bike chain around the stone, then applied pressure on the cutter handle. After a sharp crack of sound, the geode broke open and fell into his hand in two equal halves. Inside each was a beautiful blue, milky lining of quartz dotted with dark, rod-like crystals of goethite, a hydrated iron oxide.
The event also featured a black-light tent for viewing florescent minerals, videos about agates, hourly drawings, on-going silent auctions, geological tools and lapidary supplies for sale, a ton of agates, and a whole flock of agate-lovers more than happy to show their favorite finds to the droves of rock hounds who came to see them.
Courtesy Mark RyanI think my favorites were the three stunning grapefruit-sized agates that grace the cover of a recent book titled Agates of Lake Superior written by Dan and Bob Lynch from Two Harbors, Minnesota. They had all three beauties on display. Two were found in the Two Harbors area, and the other in a gravel pit near Forest Lake, MN.
Courtesy Mark Ryan CollectionIn 1879, on the High Plains of Wyoming Territory, fieldworker William Harlow Reed discovered the first bones of a nearly complete dinosaur skeleton that Yale paleontologist Othniel Marsh would eventually name Brontosaurus excelsus. Arthur Lakes (another of Marsh's fieldworkers) made a watercolor portraying Reed (right) and helper Edward Ashley sitting among the sauropod's bones at Como Bluff's Quarry #10 (scroll to bottom of link page to see the painting). More about the discovery can be found here. The mounted skeleton still stands at Yale's Peabody Museum in New Haven, Connecticut.
Courtesy Mark Ryan
The long spell of unusually hot weather (see Thor's post) may have you looking for some relief, so let me suggest you head for northern Minnesota. No, I’m not talking about Duluth or the North Shore of Lake Superior (it’s been hot there, too), but way up north to the Soudan Underground Mine State Park on the southeast shore of Lake Vermilion (Map). The Soudan Mine is one of several underground mines that once operated in the Ely area, and was the oldest and deepest mine in Minnesota. It’s the perfect place to bring the whole family to learn about Minnesota’s iron mining past and descend a half mile into the earth where you can experience for yourself what it was like to work in an underground mine. An added perk during these steamy summer days is the fact temperature in the mine year-round is a cool 51°F.
In June, my brother Pat and I made one of our frequent geo-tours north, and this time our primary goal was to visit the Soudan mine. After some time exploring Manitou Falls near Superior, Wisconsin, and the eerily fog-shrouded Palisades on the North Shore, we made a beeline up to Ely where we spent the night. The next morning we drove the twenty miles west to Soudan, arriving just after 9am. As we neared our destination, the headframe of Shaft #8 could be seen looming above the ridge-line, making it fairly easy to find the park. Shaft #8 is the operational shaft that takes you underground.
Courtesy Mark RyanThere are two tours into the mine available to the public: the High Energy Physics Lab tour and the Mine History tour. These are separate tours and can't be taken together, and since our time was somewhat limited, Pat and I opted for the history tour. It was slightly longer (about 90 minutes) , included some geology, and seemed like the way to go. So we bought our tickets and while waiting for the tour to start, we checked out the grounds and buildings where the implements and artifacts once used for mining can still be seen. These included the crushing house, the dry house, and drill shop.
Courtesy Mark RyanThe machinery in all these buildings stand idle today, but not so with the engine house. The equipment there still drives the cables and hoist that delivers visitors to and from the mine. Beneath the headframe, Pat sighted several bats fluttering up from the shaft. Three bat species inhabit the mine: the little brown, Eastern pipistrelle, and Northern myotis. But don’t worry, they weren’t any bother at all during the tour.
Across the road from the headframe is a deep, long gash in the ground overgrown with vegetation that was once one of the original open pit mines. Staring down into the hole, it’s not hard to imagine the difficulty the miners faced extracting ore from its steep walls. Pat and I didn’t have time to take the hiking trail far enough to see the much-photographed Soudan Iron Formation outcrop – something I regret - but we did see a couple other open pit mines on the property.
Courtesy Mark RyanThe first iron ore mined in Minnesota was taken from an open pit in Soudan, and shipped by train to Two Harbors at Lake Superior in the early 1880s. The promise of gold had attracted a lot of prospectors to the Arrowhead Region of Minnesota, including George Stuntz, a Duluth civil engineer who established the Vermilion Trail into the area. But instead of gold, he found iron ore. The Vermilion Range, with its rich iron ore, would be the first of several major iron ranges discovered across northern Minnesota. In nearly 80 year of operation, Soudan produced nearly16 million tons of rich iron ore that were shipped across the Great Lakes to steel mills in the East or in later years, sent by train down to the steel mill in Duluth. (I worked at the US Steel mill in Duluth for a year. My first job was on the high-line tracks where iron ore and other steel-making materials were delivered by train to the open hearth furnaces. During lunch, I’d watch my co-workers tap the furnaces. When the molten steel was ready to go, alarms and sirens would sound as a small bomb was sent into the furnace that would blow out the plug, forcing the molten steel to pour out into giant multi-ton ladles. Very impressive and extremely noisy!).
At 10am sharp we gathered with other visitors for the tour. After a quick video explaining an overview of the mine and its history, everyone grabbed a hardhat and loaded into the shaft’s elevator or “man cage” as the miners called it. A dozen of us crammed into the cage for the ride down. It wasn't too bad but it bordered on stuffy, especially in the heat. Our tour guide, a very pleasant young woman, eagerly imparted her knowledge of the mine’s history and the safety issues involved with the tour. She informed us that back when the mine was operational eighteen miners usually wedged into the cage for each transport.
Courtesy Minnesota Geological SurveyThe ride down to Level 27 took under three minutes. The shaft is angled about 78 degrees so besides traveling half a mile underground we also moved 500 feet north of the headframe and underneath the nearby old open pit mine. During our rattling, rapid descent, our guide held her flashlight against the scuffed window so we could see something - the occasional reflection of dim light as we shot past levels - otherwise it would've been a pretty dark ride. Two levels (#12 and #22) were lighted because they’re still used to pump out the relatively little water seeping into the mine.
Courtesy Mark RyanLevel 27, the deepest level in the shaft, was lighted, too, at least where the elevator stopped. The physics lab is located on the same level and we could see its entrance as we exited the elevator. We were joined by a couple more guides who herded us into small rail cars for the last leg of the trip, this time horizontally through a dimly-lit 3/4 mile passageway called a drift. The mineshaft and drift were dug out through Ely greenstone. As promised the temperature in the mine was a cool 51°F and a refreshing break from the surface heat. At least I thought so. Some folks were wearing sweatshirts or light jackets, but I was comfortable in just a t-shirt and shorts.
Courtesy Mark RyanAt the end of the tunnel we detrained and were led up a metal spiral staircase (the miners used ladders) to reach the stope, a large, cavernous space carved into of the ore layer. Our guide pointed out some of the geological features including adjacent greenstone layers, mineral veins of copper, and of course, hematite. She explained how holes were drilled into the walls of the ore body, and explosives placed inside for blasting. After the controlled explosion, and before any miners were allowed in, a barman was sent in to knock down any loose rock from the ceiling. Barring was one of the higher paying jobs in the mine but probably the most dangerous.
The miners used the “cut and fill” method to mine the ore from the ceiling. Waste rock was let drop and used to create an ever-rising artificial floor that remained pretty much the same distance from the ceiling being mined. This eliminated waste rock disposal to the surface. The dense ore, which weighed as much as 325 pounds per cubic foot, was sent down chutes into granby cars on the level below them for transportation back to the skip that carried it up to the top. The granby cars and skip each held 6 tons of ore and miners were paid according to the amount of ore they sent up to the surface. There, the ore was dumped into larry cars and transported to the crusher house for crushing, then either loaded into waiting train cars or stockpiled for later shipping.
Courtesy Jvstin via FlickrThe iron deposits found at Soudan precipitated out of an ancient sea during the Early Precambrian period about 2.7 billion years ago. The iron was deposited on pillow basalts extruded during earlier volcanic activity. Pillow basalts form when molten rock comes in contact with water. The iron, which also originated from volcanic activity, interbedded with deposits of mud and sand forming what’s called a banded iron formation or BIF. Unlike the large and extensive single bed of iron ore occurring in the Mesabi Range, the iron ore at Soudan was laid out in small lenses. More pillow basalt flowed atop the iron layers. Later, probably through hydrologic processes, the iron content was enriched and the entire sequence tightly folded and deformed by tectonic forces from regional mountain-building episodes (orogenies) and later baked by the underground upwelling of magma during intrusion of the Duluth Complex gabbro. The heat and pressure metamorphosed the sequence, transforming the basalt into Ely greenstone (shist). The entire sequence eventually ended up nearly vertical in an anticline with layers of hematite, jasper, and chert sandwiched between layers of greenstone (also known as chlorite).
Miners working the underground mine at Soudan often referred to it as the “The Cadillac of Mines”. Compared with other underground mines near Ely, it was relatively dry, the temperature was a comfortable 51 degrees year round, and fresh air permeated all the levels. But to show that it wasn’t all rosy, our guide demonstrated what it must have been like for the miners before electricity. The mine chamber was well lighted for us tourists but to give us an idea what the early miners experienced she extinguished all the lights and held a single burning candle near her face. It wasn’t very bright at all and kind of spooky.
Courtesy Mark RyanLater, when electricity was put in, lighting improved, and power drills were used in the mining process. After a sufficient warning, our guide played for us a recording of the sound made by a single drill at work just to give us an idea of the noise level produced. The decibel level I remember from working in the steel mill was nothing compared to what the miners must have endured when several drills were going at once. It’s no wonder many of them suffered hearing loss after years working the mine.
As steelmaking processes were refined, the need for Soudan’s rich ore diminished. Using low-grade iron taconite became more economical for use with new oxygen-fed furnaces. Soudan shut down operations in 1962. The next year, after all the stockpiled ore had been shipped, US Steel Corporation gave the mine and an additional 1100 acres of land to the state of Minnesota for $1. The stipulation was that the site be used for educational purposes. Minnesota turned the site into a state park in 1965.
Courtesy Mark RyanI found the Soudan Underground Mine State Park well worth the trip. Where else can you travel a half-mile underground into 2.7 billion year-old rock formations and cool off at the same time? (The temperature at the bottom of the Grand Canyon is much hotter than at the top). Soudan's a great place to learn about Minnesota mining history, see area wildlife and check out some of the unique geology in the Lake Vermilion region that helped make Minnesota a leading iron ore producer.
Entry to the park is free and requires no state park sticker. The mine tours, however, require a fee. Pat and I paid $12 each. Kids are cheaper. The tours begin on the hour from 10am to 4pm daily. Tours for the High Energy Physics Lab occur only twice each day, the first at 10am and the second at 4pm. As I mentioned before, you can't combine tours so you have to pick either the historic one or the physics one. Mine tours are available from late May until the end of September. Follow this link for additional information.
On our way home, Pat and I agreed we'd come back sometime soon for the High Energy Physics Lab tour where physicists investigate things like the particle mass of neutrinos, and detect other dark matter particles. The lab is run by the University of Minnesota. However, I recently learned there’s a third mine tour available at Soudan, one offered only to organized groups. This one is more geology-focused and instead of riding the train through the 3/4 mile of Ely greenstone to the ore body, participants walk through the drift and are given a detailed lesson in geology along the way. I definitely have to join me up with one of those groups. Maybe next summer.
Did I mention it’s 51°F in the mine?
Short video of Soudan Underground Mine tour
Minnesota mining history
More DNR Soudan info
Gigapan of Soudan Mine site
Soudan at Wikipedia
DNR Soudan Mine site
MN Conservation Volunteer article on Soudan Mine
The Denver Post website contains some tragic and spectacular photos of the wildfires blazing in the foothills west of Colorado Springs. Tens of thousands of people are being evacuated as whole neighborhoods are going up in flame, The wildfire doubled in size overnight and is now nearing Garden of the Gods. The park has closed until further notice.
I've been checking out some of the visual material taken of yesterday's massive flooding in Duluth and thought this one was pretty interesting. The video of the raging Miller Creek in Lincoln Park was taken while it was still raining and you see can visible change in the water level by the end of it.
Courtesy Mark RynThe recent floods in Duluth and other communities in northern Minnesota illustrate the incredible erosive power of running water. I was living in Duluth in 1972 when floods then ripped up the entire length of 6th Avenue East from top to bottom. This go-round appears to be even more devastating. I was particularly saddened to hear that the Swinging Bridge at Jay Cooke State Park has been destroyed by the force of the St. Louis River. The Lake Superior Zoo was inundated with water killing several of animals there. Several animals escaped, including the polar bear which was quickly tranquilized, recaptured, and sent to Como Zoo in St. Paul. One seal was more successful in its escape and made it out of the zoo compound to Grand Avenue where it stopped traffic. Recovery from all the damage is going take a while.
Last month's earthquakes in Northern Italy produced some interesting examples of soil liquefaction, a phenomenon, that occurs often during earthquakes when soil or other uncompacted ground material suddenly loses its strength and structure and begins to act like a liquid.