So, one of the first times I visited
the Keweenaw Peninsula, way up in the most northwest part of Michigan, we
rounded the corner on the highway, and I giggled like a small child. Because
having grown up near Detroit, I thought that Michigan was a relatively flat state. But
in front of me, was a gorgeous, giant cliff. Watching it roll into the
distance as far as I could see, I distinctly remember thinking it looked like
a dragon spine. And I immediately wanted to know what it was. In a state dominated by
flatlands, where did this cliff come from? To my utter shock and delight, it turns out, this is possibly the single largest lava
flow on the planet. It's story time. Before I get into that story, though,
I want to tell you about a bar. As the story goes, one day in 1843,
a man in his late 30s named John Hays was treating some folks to drinks in
Copper Harbor, Michigan. Even today, Copper Harbor is a very small town, but in 1843,
it was more or less a collection of tents — so, however developed you’re imagining this bar
to be, maybe take that down a few notches. Hays was traveling from Pittsburgh, and
he was in Michigan partly for his health, but partly to check out the copper scene. Americans and Europeans had known there was copper
in this region (called the Keweenaw) for decades, but they still recognized this land
as the territory of the Anishinaabe, who’d been there for centuries. That
changed in 1842, when the Treaty of La Pointe was signed with the Anishinaabe,
and colonizers officially took the land from them. You can learn more about that
in the description if you're interested. So, one year later, John Hays is standing
around this bar in Copper Harbor, when a guy from Boston named Jim Raymond has a bit of
an outburst. I’m going to censor this quote, but essentially, he said, “I
got three of the best claims on the Keweenaw — pure copper sticking
right out of the greenstone on one of them — and I can’t raise a cent to take
the stuff out. What I need is a partner.” So, Hays got this guy another
drink, and not long afterward, they’d drafted an agreement on the back of an
old letter that gave Hays and one of his buddies the opportunity to buy a one-sixth interest
in Raymond’s claims, for the sum of $1000. Jim Raymond had the mineral rights to three
parcels of land, including one close to the nearby town of Eagle River. And that piece of land
in particular turned out to be something special. Now, how exactly this next
event unfolded isn’t clear: There are multiple stories and competing
accounts, and some are more likely than others. One of the more dramatic accounts is that in Fall
1844, John Hays and some of his buddies are out on his boat. It’s November on Lake Superior,
which is a notorious time for violent seas, so Hays and his companions get caught in
a storm and blown ashore. Then, they start walking back to town when, supposedly, someone
spots a small vein of copper in the cliffs. If I had to guess, this isn’t exactly how
that went down. But one way or another, someone saw a glimpse of metal in those
Eagle River cliffs. And they kickstarted a chain of events that would break down
this region and rebuild it as a place so populated and wealthy that it was
known by people around the world. But really, what these people stumbled upon, were the remains of a cataclysmic event
that happened more than a billion years ago. About a hundred years after John Hays
stood around that Copper Harbor bar — so, in the 1940s — researchers noticed something
interesting about the Midwest United States: In certain spots, the pull of gravity was stronger
than they expected. It’s not anything you or I would notice in everyday life, but it's something
they could pick up on with their instruments. They traced this gravitational anomaly
from Kansas, up to Lake Superior, and down toward Detroit — and today, we know it
may stretch a bit farther in both directions. How strong the pull of gravity is, is
related to how dense something is. So, if these spots had a particularly strong
gravitational pull, and there was no obvious culprits on the surface, that suggested there
was probably heavy, dense rock underground. And later, scientists learned that's
exactly the case: There is a snake of dense, mostly-volcanic rock under the surface. And
there’s only one area where it really rises above the ground: the area around Lake
Superior. Where I’m currently standing. This rock is cooled lava. But it’s not from the
kind of volcanic event you might be picturing. See, about 1.1 billion years ago, back when
organisms like algae were among the most complex life on Earth, something extraordinary happened
here: The continent started to split apart. Now, this has happened plenty of times throughout
history: It’s happening right now in eastern Africa, for instance. But the remarkable thing
about this event, was that it failed, in a sense. Essentially, a rift is considered
successful when it splits so completely, it forms a new ocean. And this rift — now called
the Midcontinent Rift System — well, it got a good part of the way there, flooding the surface
with millions of cubic miles of lava as it went. But after millions of years… the
continent stopped splitting. If it hadn’t, I would likely be standing
on the shore of an ocean right now, or in a boat. But instead, this area was
left with layers upon layers of lava flows. Some of these flows are pretty small, and would’ve
cooled and hardened relatively quickly. But others are bigger. And one flow in particular is
so large, and filled up a valley so deep, that according to one interpretation of the data,
it was likely molten for thousands of years. It’s called the Greenstone Flow, and it is
among the largest lava flows on Earth by volume. In fact, the highest estimates put it at
more than 1400 cubic miles, which would make it, by volume, the largest single lava flow on the
entire planet. And I’m standing in front of it: separated from a potential lava sea
by about a billion years of time. This is the cliff I saw on my first
trip into the Keweenaw. And this is the cliff where John Hays — or who knows
who else — first saw a thin vein of copper. The vein they spotted in the Greenstone Flow
wasn’t much. It was only a few inches wide at the top, although it did open up to two feet
wide farther down. Still, it was promising. So, not long after this discovery, miners drove
a horizontal tunnel about 70 feet into the cliff to investigate further… and they found
an enormous mass of virtually pure copper. This was the first documented time
anyone had found a mass of pure, native copper in place in the rocks like this;
before, it was always copper that’d been scraped up and moved somewhere by the glaciers. So,
presumably with dollar signs in everyone’s eyes, work seriously began at the Cliff Mine in
1846, and the metal seriously piled up. In July, the Cliff produced more than 500,000 pounds of copper. The only other copper producer
in the region produced about 5000 pounds. The next year, the Cliff shipped out 1.5 million
pounds of copper at the end of the season. And the following May, in 1848, they
averaged 100,000 pounds of copper per week. Now, this place wasn’t like the Quincy Mine, which
I’ve talked about in earlier videos. At Quincy, miners would often find big pieces of copper,
but mostly, the pieces were relatively small. At the Cliff, it was the opposite: In
the late 1840s and going into the ‘50s, the major pieces of metal were massive. Like, one report describes an 83-ton
piece of virtually pure copper. In fact, the pieces of copper at the Cliff were
so big, that chiseling them apart and hoisting them from the mine took about
a third of the mine’s time and money. Now, working at a mine in this era could be
incredibly dangerous, so it wasn’t a gilded, sparkly time for most people working
underground. But it was a deeply productive and profitable operation. And again, they had
a billion years of geologic history to thank. Now, not all lava flows have a significant
amount of copper in them. In fact, not all the lava flows in the Midcontinent Rift system
have significant amounts of copper in them. So, what makes the Greenstone flow and
the surrounding area so special? Well, I got to talk with Dr. Laurel
Woodruff about this a few months back while working on a completely different
project. She’s a research geologist with the US Geological Survey, and has spent a
lot of time studying the Midcontinent Rift. She told me that the copper here came
from the Rift’s older lava flows. See, during this event, flow after
flow poured out on top of one another, and cooled into a pile of basalt tens of
miles thick. And that pile was so heavy, it sank under its own weight
beneath what’s now Lake Superior. Over time, that buried rock
heated up, was chemically altered, and released its copper atoms. That formed a
scorching-hot fluid full of the stuff. Then, millions of years later, something key
happened: In what’s now the Keweenaw Peninsula, another event lifted up the edges of the
rift, and that fluid started to move, traveling through the cracks
and gaps in the lava flows. When that fluid cooled near the surface, it
deposited its copper. And ultimately, the rocks of the Keweenaw Peninsula became especially
enriched in copper. With this cliff in particular, the fluid flooded enormous cracks in the rock,
leading to those gigantic, pure deposits. So, a large part of the reason the Cliff Mine was
so successful wasn’t just because it’s located along the Midcontinent Rift. It’s specifically
because it was located in the Keweenaw. So, the Cliff Mine had a lot to work with,
and they did incredibly well into the 1860s. For instance, they installed the first man
engine in North America: a sort of mechanized ladder that saved workers from having to
climb long distances. And people-wise, a whole town called Clifton had sprung up nearby.
In 1860, it was home to about 1400 people — the majority of whom weren’t miners. Clifton had
multiple churches, blacksmiths, a school, and more. And you can still see remnants of
it — notably, two of the town’s cemeteries. But for as lovely as this was, the copper
in the cliff wasn’t unlimited. By 1860, the mine had started to run out of big pieces of copper, and almost half of their
production came from smaller bits. By late 1870, even most of that
had run out, and the primary vein of copper they’d been following had
dwindled to only a few inches wide. So, in December 1871, about 25 years after
mining really began, the company that owned the Cliff sold the property. And essentially,
the mine’s heyday was over. Activity continued on a smaller scale and with new owners for a
few years, and over the next century, people occasionally explored the area. But the mining
was, for all intents and purposes, completed. Ultimately, the Cliff has been considered
the first major mine in North America, and it set the stage for
all the history to follow. After mining at the Cliff stopped, the Calumet
& Hecla Mine, the Quincy Mine, and many more continued carrying the torch — wrenching copper
from the earth and sending it off to build the growing United States. It was incredibly
dangerous, destructive, and important labor. But while places like the Quincy are still
somewhat preserved, the Cliff Mine and the town of Clifton are basically claimed by the forest. It’s
been about a century since anyone lived there, and as I worked on this video, I kept wondering
how we even know what life was like for them. And in the end, to learn more about this
human side of the story, I got some help. I met up with Dr. Sean Gohman, who started
Michigan Tech University’s Cliff Mine Archaeology Project back in 2010, and he gave
me some incredible insights not just into what the Cliff was like, but how you figure that out
starting from ruins. But more on that next time. For now, thanks for being here. I hope
you learned something that makes you think about the world just a little
differently, and I'll see you soon.
