I thought it might be interesting to share a couple of the things that we encounter because of living in a place that gets so cold in the winter that the ground freezes deep down. Here is a quote from the Canadian Encyclopedia article about permafrost.
About 50 per cent of Canada is underlain by permafrost, mainly in the Arctic Archipelago, Yukon, Northwest Territories and Nunavut. In permafrost regions, the upper layer that undergoes seasonal freezing and thawing is called the active layer. Below this lies the permafrost, the upper surface of which is called the permafrost table.
Here in Northern Alberta where my family lives, we are in a region of permafrost called Sporadic Permafrost. This depth of ground freezing doesn’t happen every year. But this winter season, we had snow on the ground for six months and colder than usual temperatures for longer than we have had in several years.. That contributes to the ground frost going deeper and freezing harder than in other years with warmer temperatures, and a shorter cold season. Here are some pictures of what happened to our gravel roads when the spring came.
This one doesn't look like much, but it has been there a while, and it is never in the shade, so it probably melted underneath already, and is being packed down by traffic.
This is the first year that I have seen it this pronounced. At first, I did not know what they were. They look like extra large humps in the road. I noticed that they were wet, like it had just rained on them... and only them. Here is another one. See how it is wet and the ground around is dry?
Here is another quote from the Canadian Encyclopedia. It turns out this phenomenon has a name: Pingo:
Pingos are ice-cored mounds up to 100 m high. They are formed when water in the ground changes to ice and expands so that the resulting ice masses force the overlying ground upwards.
They are not very good for the undercarriage of your car either. One caught me by surprise last week, and I was sure I ripped out the bottom of my car. It sounded terribly destructive. I am lucky that I live across the county road from my auto mechanic. I had him look at it, because I was pretty sure I had broken my car.
I am very lucky… this time. There were a couple of pebbles caught in some critical places that he removed for me. And my car will be okay to continue transporting me to all the places I go.
So, I mentioned earlier that these humps seem to be wet while everywhere else is dry. It turns out that it is literally the ice from underground expanding upward and pushing the ground up. The reason for the humps, is from the forces described in the quote, and where they occur on the road would be because of the traffic of cars, light trucks and tractors that regularly travel a county road. The wheels of the traffic push the melting underground ice down with their wheels and the force of the expansion of the ice creates the humps in the road. When this ice reaches the warm surface air, it melts, making the ground wet.
Something else, that I cannot really show a picture of is the phenomenon that happens in the basement of our homes during the winter. Our basement right now is what I would describe as super-cooled (right now the temperature in the basement reads 60 F/10 C, while upstairs the temperature sits at 72 F/24C) in comparison to the main level. This is, again, because of the freezing temperatures that happen in the ground around the house and cause the basement to hold that cold (like a root cellar). As the summer season progresses, the temperature difference between the basement and main level will gradually become less. But here is a the ‘cool’ thing I discovered a couple of summers ago: We have a separate switch for the fan to our central heating system. When the furnace is running, this fan recirculates the air throughout the house with the intent of drawing cool air in from along the floor and running it through the furnace to warm it before it is blown out into the rooms through the floor vents.
This recirculating fan also works like a hot damn for drawing the cool air from the basement and blowing it out onto the main level on a hot spring or summer day. Blessed relief for those of us whose bodies have become accustomed, in the previous six months, to living with below-freezing temperatures outside.
I hope you enjoy this little excursion into a northern Alberta spring experience.
A final picture of the 'greening':
