The Permafrost Beneath Dawson City

The building permit office in Dawson City keeps records that tell a story about the ground beneath the town. You can see it for yourself just walking down Front Street: the older gold rush-era buildings lean at angles that were never in anyone’s blueprints. Some of them have been leaning for so long that they’ve more or less settled into their new shape. Others are still slowly on the move, as the permafrost beneath them keeps reacting to the heat of people living, working, and partying above. Permafrost is ground that has stayed frozen for at least two years straight. Around Dawson, that frozen layer can run down several hundred metres in places, a deep reservoir of cold that, in spots, has held steady since the last ice age. It’s ancient cold, stored in the earth. And up here it isn’t an abstract scientific idea — it’s one of the basic facts that quietly runs your life. The gold rush stampeders who poured into the Klondike in 1897 and 1898 ran into permafrost almost as soon as they picked up a shovel. The gold-bearing gravels in the creek valleys were locked in frozen ground, and getting to the gold meant figuring out how to thaw the earth first. The methods they worked out — wood fires at the start, then steam thawing pipes — were some of the most important practical technologies of the whole rush. Without them, the gold might as well have been poured behind a concrete wall. ## What Permafrost Is Permafrost isn’t just frost with better branding. Frost is the surface freezing that shows up every winter across temperate and subarctic regions, the stuff you scrape off your windshield. Permafrost is different: it’s soil that has stayed below zero degrees Celsius long enough for the cold to reach through its whole depth. Each winter, the seasonal frost that works its way into the ground is called the active layer, and it thaws out again every summer. Beneath that, where the temperature never climbs above freezing, is the true permafrost. Around Dawson City, that active layer is usually somewhere between half a metre and two metres thick, depending on vegetation, soil type, and which way a slope faces the sun. Below that, the permafrost can stack up for hundreds of metres. The boundary between the two — the permafrost table — quietly sets the rules for a lot of what can and can’t be built in the Yukon. There’s ice in that frozen ground. Sometimes a little, sometimes a lot. In some formations, the frozen soil is so rich in ice that when it finally does melt, the ground slumps and buckles dramatically. That’s called thermokarst, and it’s one of the big headaches in a warming climate. As average temperatures creep up, the permafrost around Dawson is thawing from the top down, and the results — collapsing ground, slope failures, and shifting drainage — are already written on the hillsides if you know where to look. ## Mining the Frozen Ground When the first Klondike miners pushed into the creek valleys in the fall of 1896 and started sinking shafts, they discovered that the ground was frozen solid ten, twenty, even thirty feet down before they reached the bedrock where the gold had settled. Summer panning — the standard way of working unfrozen placer deposits elsewhere — simply didn’t work. So they turned to fire. Miners built wood fires directly on the surface, let them burn for hours, then shovelled away the thawed muck. Then they lit another fire, and another. It was slow, smoky, and more than a little dangerous — especially once they were working in tight underground drifts where a fire could turn a shaft into a chimney. But it got the job done. Those first Klondike miners managed to pull gold out of frozen ground before the real winter locked in. Within a few years, steam thawing had edged out open flames as the main method. Boilers on the surface pumped steam through metal pipes driven down into the frozen ground. The steam ate through the permafrost much more quickly and allowed round-the-clock work without open flame in confined spaces. The basic technology came from other mining regions, but it was adapted in very particular ways to suit Klondike permafrost. ## The Mammoths in the Muck One of the stranger side effects of mining frozen gravel was what turned up in the thawed muck and the freshly exposed hillsides above the valley floors: pieces of the Ice Age. The Klondike is one of the richest Pleistocene fossil regions in North America, and permafrost is the reason why. The same cold that locked gold-bearing gravels in place for thousands of years also preserved the bodies of animals that died in these valleys fifteen or twenty thousand years ago. Woolly mammoths, steppe bison, ancient horses, cave lions, short-faced bears — the fossils that come out of Klondike permafrost paint a picture of an extinct community of animals that once roamed this country. Miners were finding bones and tusks as early as the gold rush years, and those discoveries have continued ever since, especially when new cuts expose permafrost that’s never been thawed or disturbed before. The most famous permafrost mummy in the broader Beringia region is probably "Blue Babe," a steppe bison recovered from a placer mine north of Fairbanks, Alaska, in 1979. On the Canadian side of the border, Klondike mines have produced their own remarkable specimens. If you’re curious about that deep-time world, the Yukon Beringia Interpretive Centre in Whitehorse — my pick for the territory’s best natural history stop — has a collection that makes the Ice Age Klondike feel real in a way no textbook ever will. ## Building on Frozen Ground During the gold rush building boom, no one fully understood what it meant to throw up a town on permafrost. Buildings went up fast, on whatever patch of ground looked solid enough, with very little thought about what was frozen beneath. The trouble didn’t show all at once. It crept in over the years, as the heat from occupied buildings melted the ice in the permafrost below, the ground slumped, and structures started to tilt, crack, or, in some dramatic cases, sink. Modern construction on permafrost is built on a different philosophy: keep the frozen ground frozen. Newer buildings are usually set up on piles, with a clear air gap between the floor and the ground so cold air can circulate and carry away heat before it seeps into the permafrost. Utilities — water and sewer especially — often can’t be buried in the usual way, so they’re run in insulated above-ground corridors called utilidors. Roads are laid over thick blankets of gravel to insulate the ground underneath. These tricks work reasonably well as long as the permafrost stays cold and stable. They start to fall short when the background temperature is climbing because of climate change. In Dawson, several buildings have run into serious structural issues in recent years directly tied to degrading permafrost, and the town is having to wrestle with the cost and complexity of adapting its infrastructure to ground that is literally changing shape. ## The Climate Question Yukon permafrost is warming. Of all the signs of climate change in Canada, this is one of the best documented, and for towns like Dawson City it’s not theoretical. The active layer is getting deeper. The permafrost table is dropping. Ground that has been frozen since long before there was a town here — or any town anywhere — is starting to thaw. For a community built on permafrost, this hits close to home. Buildings engineered on the assumption of stable frozen foundations are failing as those foundations soften. Roads are sagging and buckling. Slopes that held together when the ground beneath was locked in ice are starting to creep and slide. Drainage patterns in the valley are shifting in ways that matter if you happen to live next to a suddenly wetter gully. The Tr'ondëk Hwëch'in, who have lived with and on this landscape for thousands of years, carry a detailed memory of how it has changed just within living lifetimes — knowledge that sits alongside, and sometimes goes well beyond, what the monitoring stations can tell you. Caribou trails have moved. Berry patches that once produced reliably have shifted. The river ice doesn’t behave the way it did even a generation ago. Permafrost is one piece of a living system that the Tr'ondëk Hwëch'in read continuously and carefully, and what they’re reading now is a landscape under stress. ## What It Feels Like Underfoot Walk up onto the hillsides above Dawson City in July and you can feel the permafrost with every step. The surface has a give to it — a mat of active-layer soil and living moss that compresses under your boots and then slowly springs back. In wetter patches, the mix of moss and water makes it feel like walking on a giant soaked sponge. On drier, more exposed slopes, the ground is firmer, but there’s still a hint of that softness that reminds you there’s ice underneath holding everything up. If you let yourself think too hard about it, it’s an unsettling feeling. The ground is frozen. Just a few feet below your boots, some of that ground has stayed frozen since long before the first person ever walked into this valley. The gold that pulled people here in the 1890s sat locked in that frozen earth for thousands — or millions — of years, depending which layer you’re standing over. The buildings you can see from the hillside are resting on the same foundation, and some of them wear the consequences plainly in their twisted doorframes and cracked walls. If you’re planning a visit, the [Dawson City Travel Guide](/guide/dawson-city-travel-guide) lays out the practical details: what’s open, what the roads are like, and which sites you can actually get to this season. The [Yukon Historic Sites: A Complete Visitor's Guide](/guide/yukon-historic-sites-guide) adds the stories behind the heritage buildings and sites around town — many of them scarred, in subtle and not-so-subtle ways, by decades of permafrost movement. The ground under Dawson City is one of the most interesting things about the place, and most visitors don’t really notice it until a leaning hotel or a century-old false-front with a long vertical crack reminds them that, here, even the foundations are still in motion.