Jul
25
2012

Soudan Underground Mine tour offers history, geology, and relief from the heat

The Soudan Underground Mine entrance: Shaft #8 headframe (center) once transported miners to various levels up and down the mine shaft. Today it delivers park visitors to Level 27 for tours of the iron ore mine. It also transports scientists to and from the High Energy Physics Lab on the same level.
The Soudan Underground Mine entrance: Shaft #8 headframe (center) once transported miners to various levels up and down the mine shaft. Today it delivers park visitors to Level 27 for tours of the iron ore mine. It also transports scientists to and from the High Energy Physics Lab on the same level.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.

The crushing house at Soudan: Iron ore from the mine was crushed here into seven-inch chunks before shipping.
The crushing house at Soudan: Iron ore from the mine was crushed here into seven-inch chunks before shipping.Courtesy Mark Ryan
There 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. Engine house at Soudan: the equipment still operates the hoist that delivers visitors in and out of the mine shaft.
Engine house at Soudan: the equipment still operates the hoist that delivers visitors in and out of the mine shaft.Courtesy Mark Ryan
The 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.

Minnesota's first iron ore mine: This open pit mine at Soudan produced the first iron ore shipped from Minnesota.
Minnesota's first iron ore mine: This open pit mine at Soudan produced the first iron ore shipped from Minnesota.Courtesy Mark Ryan
The 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.

Generalized view of Soudan Mine c. 1898: the shaft extends down 27 levels parallel to the ore body.
Generalized view of Soudan Mine c. 1898: the shaft extends down 27 levels parallel to the ore body.Courtesy Minnesota Geological Survey
The 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.

Riding through the drift: In the old days miners had to walk the 3/4 mile tunnel to the stope in the dark.
Riding through the drift: In the old days miners had to walk the 3/4 mile tunnel to the stope in the dark.Courtesy Mark Ryan
Level 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.

Level 27 stope: Our guide explains some of the rock formations found inside the mining chamber.
Level 27 stope: Our guide explains some of the rock formations found inside the mining chamber.Courtesy Mark Ryan
At 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.

Soudan Iron Formation: This banded iron formation seen at Soudan Underground Mine State Park was deposited in a marine environment 2.7 billion years ago.
Soudan Iron Formation: This banded iron formation seen at Soudan Underground Mine State Park was deposited in a marine environment 2.7 billion years ago.Courtesy Jvstin via Flickr
The 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.

Mining the stope: Mannequins fill the role miners once held in a Level 27 diorama.
Mining the stope: Mannequins fill the role miners once held in a Level 27 diorama.Courtesy Mark Ryan
Later, 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.

Mining artifacts in Soudan mine: mining equipment from the old days can still be seen in the mine.
Mining artifacts in Soudan mine: mining equipment from the old days can still be seen in the mine.Courtesy Mark Ryan
I 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?

LINKS
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

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Anonymous's picture
Anonymous says:

I would LOVE to go into that mine if it ment I could get away from the heat :)

posted on Sun, 08/11/2013 - 3:40pm

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