Let’s talk about permafrost. Otherwise known as perennially frozen ground, is a hallmark of the north parts of the planet. All plants and animals must adapt to their surroundings and this is a key factor here. Just take a look at the map, we are just a bit south and east of Fairbanks.
Permafrost occurs when the ground remains at or below freezing for a minimum period of 2 years. The soil above this that freezes and thaws each year is called the active layer. In central Yukon, 50-90% of the ground has permafrost below its surface. Around Dawson, you can find permafrost in valley bottoms, and on north facing slopes, but not south facing slopes as these are warmed enough to keep the ground thawed. In some places there is more ice than soil. More than half of Dawson City proper is built on permafrost that is 60 meters thick. It is particularly ice rich, and vulnerable to thawing, especially with global warming.
Why does this matter to the town? When the ice melts, it loses volume and the surface drops, and buildings that lack mitigation will lean. Pipes snap, roads buckle. They have a whole method for how to build here, digging down to the permafrost, packing the hole with crushed rock that can be tamped down then using wooden cribbing (footing), rather than dug foundations. Paving is done in light color material to minimize solar absorption. They ventilate under houses to keep the ground cold. And more.
There are some notable buildings in the downtown areas that are on the lean.
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