Is Salt Mined Under Chicago?

Is Salt Mined Under Chicago?

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This question about salt in Chicago

came from listener Martin Green, who says the question came to him — literally — when he was channel surfing, looking for a documentary about science or history.

The idea made sense, he says, since Morton Salt Company is based here, and they’ve got that iconic building on the Near North Side, with the Umbrella Girl smiling at commuters from the corrugated roof as they pass by on I-94.

Let’s cut right to the chase. Curious City’s Logan Jaffe came out to that building with me to shoot pictures, and the slide show she created is just spectacular. Go ahead and watch it above.

And if you’re still curious about salt in Chicago (and Detroit!), scroll down and keep reading.

OK, now for the back-story:

My first call — to Morton Salt’s press contact, Denise Lauer — didn’t get returned right away, so I called our nation’s expert on salt: Dennis Kostik, the “salt commodity specialist” with the US Geological Survey. He’s literally the nation’s expert on salt and, if there’s salt coming out of Chicago, he’s going to know it.

So? Do we have the stuff?

“Hmmm,” he says, trying to find a nice way to put this. “Well, there’s a couple of other cities, really, that have that honor. The city of Detroit has a salt mine underneath of it, that is true.”

Yep. Detroit. Cleveland, too. But not us, not Chicago. No.

Which raises some new questions, none of which Martin Green asked us directly, but there ya go; we got a hunch he’d like to know more — not less — about salt in Chicago.

  1. If there’s no salt here, then isn’t it kind of weird that we have this big salt company in town? If there’s no salt mined here, then what happens in that Morton Salt building off the highway?
  2. No fair: Why does Detroit have a salt mine and we don’t get one?
  3. What does that Detroit salt mine look like anyway?

It took a while to hear back from Morton Salt, so we’ll start with question number two.

How come Detroit has all this salt and Chicago not so much?

For this I needed a geologist. The Earth and Environmental Sciences Department at UIC connected me with professor Andrew Dombard.

Turns out he’s a planetary geophysicist — earth isn’t even his bag. (“Today I’m working on the moon,” he told me, when we met.) But he knows enough to help me. Except I’m kind of dumb, so his explanation sounds like this to me:

“The basic geology of the region” blah blah blah “minor tectonics” blah “during the Paleozoic” blah.

So, new question: What’s a tectonic?

He takes a deep breath and explains: “Tectonics” is a word to describe the forces that affect a planet’s surface, and the effects they have. Here’s the analogy that I understood: “You take a rubber ball and squeeze it — the ball gets squeezed into a new shape.”

And this turns out to be the key to understanding why there’s salt under Detroit and none under Chicago: it’s because huge tectonics took place under the ocean floor, hundreds of millions of years ago — like when dinosaurs were developing. And then … well, let’s go with another analogy first.

So: Think of the ocean like a big bathtub, and with these massive tectonics, it’s like the floor of the bathtub is just buckling and erupting — and tons of bathwater just sloshes out of the tub. Like: Enough to put all of North America underwater. Under SALT water.

Bedrock geology map of the Michigan basin. (Graphic courtesy of Michigan Tech University)

And Michigan’s what’s called a “basin,” basically a big depression in the earth. So when the ocean floors calmed down and the waters receded, Michigan turned into a giant salty puddle. The puddle evaporated, leaving salt. And then the whole thing happened again and again for hundreds of millions of years.

Illinois is a basin too, by the way, but it’s open on one side, so when the sea levels went back down, all that water sloshed back into the ocean instead of evaporating and leaving salt.

Ta-da! OK, next question:

Really? There’s a giant salt mine under Detroit?

Well, it’s more than 300 acres — YES, under Detroit — and it’s been in operation for more than a hundred years.

The Detroit Salt Company wouldn’t let me interview anybody (what that was about, I never did find out), and they don’t hardly let anybody down there, primarily for safety reasons I’m told.

But I found someone who’d been there a time or two: Dr. Ed Van Hees, an economic geologist who works at Wayne State University in Detroit.

He says if you head south from downtown Detroit on I-75, you’ll come to a huge bridge near a steel plant. Look to your right. “If you know what you’re looking for, it’s easy to see,” says Van Hees. “The most obvious thing is this huge pile of salt.”

To get to the mine, hop in an elevator (called the “shaft”) and ride straight down almost 1,200 feet. The John Hancock Building isn’t quite that tall, by the way, and if you’ve ridden the elevator there, well, that’s about how fast you’ll be headed down. (“You’re trying to get people to go to work,” says Van Hees. “You’re not diddling — dallying around.”)

You get off in a room with 32-foot ceilings. There are trucks around and the mine spreads out in a kind of checkerboard pattern; when they carve out a “room” of salt, they leave a 50-square-foot pillar to hold up the ceiling.

“The air is dry,” Van Hees says. “You can taste the salt. The area that’s currently being mined is fresh-looking, it’s quite spectacularly white. It does have that ice-rink look to it.”

But it isn’t exactly lit up like the Ice Capades. In fact, beyond the shaft — the room where the elevator lands — there are no lights at all.

“You carry a battery, and you have a lamp on your head,” says Van Hees. “If you turn the lights off, this is the darkest of darks you’ll ever see. You put your hand in front of your nose and you can’t see it.”

So: Sights. Taste. Smells?

“The last time I was underground, the smell was very interesting,” Van Hees says. “It smelled like french fries.”

That’s not the salt. The mining company was fueling those trucks with bio-diesel.

The salt mine underneath Detroit stretches more than 300 acres. (Reuther Library/Tony Spina)

So Detroit’s got a salt mine, and we’ve got bupkis. Except … that’s right: We’ve got that big Morton Salt facility on Elston Avenue. If there’s no salt underneath Chicago like Martin asked about, what happens there?

Thanks to Denise Lauer, I did finally get to find out.

What’s there? Oh, just a mountain of awesome. That’s all. If you haven’t watched Logan Jaffe’s slide show at the top of this page, just go watch it right now.

And, if you enjoyed our answer to a question about Chicago and salt that you may have never asked, well, you’re welcome! And thanks to Martin Green for coming up with it. You can ask your own questions to Curious City here.