Did you realize on the photos on Monday or on the photo above that the solar powered street light is not perpendicular to the ground? When my husband installed the lamp last fall he put it at a 90 degree angle into the ground. Guess what – the reason for the lamp’s shift from the vertical was not an earthquake or accident.
The reason is that at that point in the yard we obviously have a small permafrost lens. Permafrost is defined as soil that remains frozen for two or more years. On warmer days late fall, the lamp already started moving slightly when the active layer started to freeze up from top to its bottom. The active layer is the upper soil layer that is overlain over permafrost. It thaws every spring to a depth that depends on the energy input in the warm season and freezes again in fall.
Last summer was really warm. Thus, the active layer became very deep and my husband was able to dig very deep without hitting frozen ground. He set the lamp in and ensured that it stood straight. The metal of the lamp poll has a different heat conductivity than the soil. On the last warm days last fall and this spring and summer the lamp poll led heat faster into the ground than the soil. Furthermore, being black the lamp poll heated stronger than the soil. Thus, the active layer around the poll thawed faster than farther away from the poll. The water had nowhere to go and the unevenly distributed weight of the lamp, unequal distribution of soil material, and prevailing wind pushed the lamp in the muddy ground out of its upright position.
While this does not matter much for a lamp in a driveway such permafrost damage can be very problematic to construction when not carefully treated. There are some houses in Fairbanks that have a roof hanging thru like an old dachshund’s back, bike paths that would be a joy for every 14 year old boy as training terrain for bike rallies and streets with potholes as big as a baby-bath tube.
Now what does the permafrost have to do with fashion? Well, the soles of shoes also conduct heat. Thus, when you live in cold climate and have to wait for the bus, tram, train or car pool make sure you buy shoes that have some insulation or add an insulating sole. A second pair of socks, socks over tights, boot toppers or a thick plateau sole can do the trick too.
Photo: G. Kramm
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