1 August 2011
We got to Kidd Creek mine at 6:45 am. As we entered the mine site, we passed a billboard proudly announcing that it had been 15 days since the last accident, and someone in our group joked that 15 days wasn’t much to brag about. We laughed, a little nervous but excited at the prospect of entering one of the world’s deepest mines, to study the underground geology of the Canadian shield.
Our guides, Greg and Amy, led us to a meeting room where we were briefed on mine safety (Repeat after me: Stay with your guide, and keep your helmet on!), and then down to the changing room to get suited up. Time was short – the lift would run with or without a bunch of tourists like us – and quarters were close as we stripped out of our clothes and put on our mining jumpsuits. Deep underground it gets warm pretty fast, so Greg told us to “wear as little under your jumpsuit as you feel comfortable with”. The dark blue suits with reflective stripes were just the beginning of our ensemble. Next came the boots: big galoshes with hard, uncomfortable soles and toes that I’m convinced were designed without any idea of what a foot looks like or how it works. My first thought when I put them on was that I wished I could just wear my hiking boots, but I did what I was told. Over the jumpsuit, we wore heavy-duty belts, and we were each assigned a bright green helmet, a pair of safety glasses, and a pair of work gloves. I opted to bring my backpack too. Even though I knew it would be hotter carrying it around, it also meant I could drink from the water bladder I was carrying inside, and would make collecting rock samples easier.
So, with mining gear and backpack on and rock hammer in hand, I stumped down the hall with the rest of the geologists in the group to the waiting room for the lift. Along the way we picked up our headlamps and battery packs. The packs fasten to the heavy belt, the lamp clips to the front of the helmet. Walking along the hallway lined with row upon row of charging battery packs reminded me of the staging room for laser tag where you are assigned a vest and a gun, but the difference is that here it’s no game. The battery pack and lamp are basic survival equipment in the darkness of the mine. (Also, there were no blacklights or fog machines in the mine.)
We sat on battered wooden benches, waiting for the lift with a handful of stoic miners. A squawking voice on the intercom announced that the lift was on its way and that anyone hoping to catch it had better hurry up. And then it slid into view and the metal door groaned open, inviting us in. We crowded into the car, keeping together and trying to keep out of the way of the real miners. The lift operator was a heavyset, genial guy who joked with the miners as he hauled the steel door shut with a clang, and started our descent.
The mine elevator isn’t like your average elevator in a skyscraper. For one thing, it’s not a completely closed box. The door is about 4 feet high, but the car itself is open above that. It’s also fast, descending at around 20 km per hour. It is not illuminated other than the glow of red, green and amber lights on the control panel, so the only light comes from the few miners who have their lamps switched on. By this light, we watched the walls of the shaft rush by as we plummeted. Occasionally, we caught a glimpse of a cavernous opening and rows of bright lights, but in a blink it was gone. The lifted jostled and clanked, and the temperature rose as we went deeper. I felt my ears popping as they adjusted to the increasing air pressure.
4400 4700 feet down, we came to the end of the first mine shaft. The lift operator swung the door wide open and we stepped out into a large, well-lit cavern. It felt much like a garage, with equipment parked off to the side, and conduits and pipes along the walls and ceiling. A warm breeze was blowing, the result of huge ventilation pipes drawing air down from the surface. Amy led us down a corridor strung with lamps to the tram that was waiting to take us to the next mine shaft.
The tram itself was a simple train of battered cars, each a box ringed on the inside with a wooden bench. The railing of the car was about at shoulder level, but when people rested their elbows on the railing they were quickly scolded and told to stay inside the car. The tram seemed like it belonged in some sort of Indiana Jones ride, and that a giant boulder should come rumbling down the tunnel behind us.
We arrived at the top of the second mine shaft and as we waited, Amy cheerfully told us that normally when the miners go on shift, they are crammed together like sardines in the elevator, and that they are instructed to stand with their knees slightly bent in case the elevator cable gives way. If this happens, there are brakes in the mine shaft that stop the car, but they aren’t gentle, and in a cab crammed with people there is no way to fall sideways and cushion the impact. If you’re standing with knees locked, it is possible to crush the bones in your leg when a free-falling lift is slammed to a stop. If everyone keeps their knees bent, they all just fall to the floor of the car on their knees en masse and injuries are minimized.
When the second lift arrived, we all piled in, and made sure to stand with our knees slightly bent. The mine has two shafts because there is a physical limit to how long elevator cables can be. After a certain length, the cable is so heavy that it can barely hold itself up, let alone a car full of passengers or tons of ore. The lifts are designed to be several times stronger than necessary, so that limits the length of the shaft.
We reached our stop at 9000 feet down and stepped out of the lift. Here, the air was genuinely hot. Greg had warned us that it would feel like a summer day in Texas, and that’s actually a fairly good description. Anyone who has spent a summer in Texas knows that we’re talking some serious heat. The sobering thing is, that’s with a hugely powerful ventilation and air conditioning system running full blast at all times. Earth’s geothermal gradient is about 25 degrees Celsius (77 degrees Fahrenheit) per kilometer.
Starting with a surface temperature of about 27 degrees C (80 F), at a depth of 9000 feet (2.7 km) we should have been roasting at 95 degrees C (200 F). (An astute reader, who happens to be a geophysicist, corrected my calculation: “The geothermal gradient is, as you say, between 20 & 30 K/km, but it doesn’t start with the surface temp of 25 C. Most of the surface of the earth has a temp near 0 C — this is, of course, submarine and at high latitudes. But even subaerially, the surface has additionally heating from insolation. If you go into a cave system – e.g. Carlsbad Caverns in NM or Mammoth Cave in KY – the first thing you notice is that the temp dives down to around 10C. Then it begins to warm. So at 9000 ft, perhaps 70C is more likely than 95C. This is, of course, still butt-kicking hot and much less pleasant than a sticky summer in TX, as you point out.”)
With that in mind, I was happy to deal with the muggy summer-in-Texas temperatures in the mine.
We learned during the mine briefing video that part of the cooling system actually involves opening up huge caverns near the surface during the winter and forcing the bitter cold air through while spraying water. This coats the tunnels in thick layers of ice. Then, during the summer, air is passed through these cavernous iceboxes before being sent down to the bottom of the mine.
From the roomy and well-lit lift entrance, we headed into the tunnels. Unlike the tram tunnel, these tunnels were fresh and unlit. The walls were shattered rock covered with huge metal meshes with 4-inch square holes, fastened to the rock with giant metal bolts driven 8 feet into the rock. These meshes are emplaced as soon as possible to protect workers (and hapless visiting geologists) from the inevitable crumbling of the rocky walls. In many places, the mesh was bulged out, holding a heavy load of rocks that had spalled free from the tunnel.
The floor was rutted by the wheels of heavy machinery driving through a thick regolith of pulverized rock powder. In places, water collected and this powder turned to a sucking grey ooze. As I stomped through this, I saw the wisdom in leaving my boots on the surface, despite the discomfort of the mining galoshes.
Our first geology stop was where the blasting had exited the hard volcanic rocks and entered a layer of sedimentary rock called greywacke. We examined this contact, but it was difficult to see much geology with so much dust on the walls. Basically the only way to see the rocks was to find fragments that had fallen through the mesh and break them open with our hammers. Since this tunnel dead-ended, it was very quiet and we had it all to ourselves.
Once everyone had had their fill of the first greywacke contact, we headed up a ramp (a climb which was surprisingly tiring in the sweltering heat and unforgiving boots) to a huge metal door. One of our guides jumped up to pull a small cord, causing an ear-splitting pneumatic hiss. A few seconds later, the door swung open, leading us into the active portion of the mine. We were at a T-junction with a tunnel that spiraled downward into the ore body, but before descending, we examined a second example of the sedimentary rocks contacting the volcanic rocks that are more common in the area. Every few minutes we had to halt our rock-banging and discussions to allow a truck to pass, and in one case, a pickup truck loaded with large red boxes labeled “EXPLOSIVES” passed through the huge door we had just entered.
Our guides radioed up to the surface that we were heading down the ramp into the ore body so that no trucks would run us down on the dark ramp, and then we made our way down. At first, the ore body looked unremarkable. More pulverized, dusty rocks, restrained by the ubiquitous mesh. But a closer look revealed the glimmer of pyrite and chalcopyrite and sphalerite on the rare clean surfaces. We started banging on the rocks, striking red sparks from our hammers and revealing the ore in its glittering beauty. In places, water had trickled through the rocks, altering the sulfides to form rusty streaks of sulfates, or thin iridescent layers on the gold and silver colored crystals. The ventilation seemed poorest here in the heart of the mine, and my
safety glasses were soon fogged and streaked with drops of sweat.
Our final geology stop was a recently blasted area, parts of which had not yet been meshed in. We scrambled around on the rock fragments, but were careful not to stray into the unprotected areas. Finally, it was time to wrap up our visit, so we tromped back up to the lift to await our ride to the surface.
By coincidence, the lift was already on its way, so we didn’t have to wait long. When it arrived the operator said that he’d be happy to take us now rather than make another trip, he just had to pick up a miner before we headed back to the surface. So we piled in, and watched in disbelief as we went even deeper. Down, down, to the bottom of the second shaft. 9800 feet below the surface of the earth. The bottom of one of the deepest mines on the planet. The lift door swung open, and a sweat-streaked miner stepped aboard. Under the small sign that said “9800” we saw a tunnel stretching off into the darkness, lit only for the first few dozen feet. It was difficult to fathom that we were 1.85 miles (3 km) down, deep into the heart of some of the oldest rocks on earth. Above us was an incomprehensible weight of stone.
As quickly as we arrived, the door slammed shut, and we were rising. The temperature cooled perceptibly, and soon we were back on the tram and then waiting for the second lift. We discovered that the main lift was down for routine maintenance, so we walked through a narrow corridor to the backup elevator. This elevator was much smaller, no bigger than a small closet, and had room for six people, packed like sardines. We rode up in batches, but when about half of our group had gone up, we heard on the radio that an injured miner was on his way up. The lift arrived, and a miner emerged from the tunnels carrying a battered plastic office chair, labeled in black marker “emergency chair”. This was placed in the tiny elevator, and then a few minutes later, a dazed miner, supported by his friend, made his cautious way to the lift. It was my turn to ride up, so I and one other member of our group joined the lift operator and the miners.
When the lift reached the surface, I stepped out into blessedly cool, almost chilly air. We let the injured miner go first, and he made his slow way up the stairs. It wasn’t clear exactly what was wrong with him, whether he had hit his head, or passed out from the heat, or hurt his leg. But he was clearly dazed and barely made it to the top of the stairs.
Changing out of the mining gear was a relief, and the previously stuffy locker room felt wonderfully cold as I removed the tortuous, mud-caked boots and sweat-drenched coveralls. We ate lunch in the conference room, and then finally thanked our hosts and bid farewell to the mine.
On the way out, I glanced again at the sign proclaiming 15 days without injuries and thought of the miner who rode up with us in the tiny elevator. For all the safety measures in place, mining is a dangerous profession. After just a couple of hours at depth, our group was very happy to be back on the surface. Even working in a modern, well-ventilated, state-of-the art mine like Kidd Creek would be miserable. As our lift operator joked, as we rose from the 9800 foot level, “This is the closest to hell I ever want to get!”
While the miners continued to work, we went on with our day – visiting a few outcrops and admiring the rocks – but I think most of the groups’ minds were still on the mine. In the car on the way back to our hotel, we talked about how hard it would be to come to grips with working in a place like that. It is thoroughly unnatural, and the mind refuses to accept that you are three kilometers underground. As newcomers, every noise, every light was strange and startling, and it was mentally taxing just being down there. As one of the guys in my car put it, it felt like “people just weren’t meant to be that far underground.”
But humans are ingenious, and we specialize in finding ways to live where we were never meant to. We learned to wear warm clothing and store food to survive bitter winters. We learned to sail the seas for months at a time without sight of land. We ride submersibles to the bottom of the sea, and rockets into the void of space, and return to tell the tale. And, in our search for resources we plumb the depths of the Earth, undertaking phenomenal feats of engineering to extract metals from the stone. To me it’s a reminder of how adaptable we are, how capable, and how unstoppable. We are a species that can do anything if we put our minds to it. The question is, what will we put our minds to next?