Over the weekend, Kathy Jones sent in this photo of plowed snow along Goodfellow Road in Hanover, with a question: What caused what’s left of the snow to look like that?
Several Daybreak readers responded with their guesses. Your choice:
Jeff Cox writes:
Lots of possible answers for the sine wave snow piles! My suspicion is that it's the same fundamental reason for washboard roads, but a visible result of the plow's interaction with the road. As the plow truck's suspension bounces up and down, so does the plow. And the plow has its own bouncing frequencies, independent of the suspension. The combination of the two can result in the plow bouncing up and down on the road surface. You'll often see this as a pattern of gouges in the road. As it does, the amount of snow plowed up per unit of time will also change. The movement of the snow from the point of road contact to the side of the road will also undoubtedly be a complex function of the plow movement. I certainly haven't worked it out mathematically, but I bet someone has. But the snow will get pushed around in three dimensions by the plow's movement, and a sinusoidal input of the plow height above the road could easily result in a sinusoidal output of the shape of the pile of snow on the side of the road.
And Jack Taylor theorizes:
Seems the answer is lying in plain sight: unevenly distributed gravel. Snow under dark-colored gravel will melt faster than unadulterated snow. In spots where the gravel layer is thicker, the gravel will soak up and store more heat and give it off well after the sun or ambient heat that warmed it up has diminished. The uneven distribution of the gravel's weight may also play a role, hastening melting under thicker layers.
Meanwhile, Jane Ashley writes:
I think the snow is heavy and wet so doesn't flow off the plow's surface, just saw the same thing down in MA where they, too, had wet snow.
John Carroll adds a gloss on that point:
About the ’sine wave’ snow piles at the edge of the road:
As the plow-truck moves forward, its plow is set at an angle to push the snow sideways toward the edge of the road. If the snow is dry, it slides easily off to the side, in a powdery plume. But if the snow is wet — think of how easy it is to make a snowball with wet snow — it’s much heavier and the snow clumps together as the plow works to slide it sideways to the road’s edge. What you get with wet snow is a lumpy windrow at the road’s edge, with dense clumps of snow interspersed with lighter snow from other storms.
Compacted snow melts much more slowly than lighter snow — think of how your child’s snow-man was always the last snow to melt. So, as the weather warms, the uncompacted snow at the edge of the road melts more quickly, leaving behind the dense, wet clumps — creating the wavy pattern you see in the photo.
And Neil Hochstedler checks in with:
As someone who's plowed snow for too many years, I have to (conditionally) agree with the snow clumping/plowing observations but point out additional influences on the melt pattern.
While dark gravel absorbs more radiant heat from sunlight than white snow, there's another method of melting - heat from air temperatures above freezing. The gravel (or any other material) acts as an insulator and prevents snow from melting. Snowbanks melt as a combination of the two, but in my experience the insulating method predominates.
Look closely at the picture. The least melted, highest parts of the snowbank have the most gravel on them. If the conduction theory applied exclusively, they would be the lowest. So it's a combination of the two, plus how the snow was originally deposited. (BTW, grass and dirt have an even more pronounced effect because they insulate more.)
Lots of factors apply: Sun, or not, warm air, or not, and which predominated. How much gravel/dirt/grass is on top of the bank. The pattern of the original deposition.
Oh, and why was more or less gravel deposited in different places? Or does it just seem that way? Did the snow melt move the gravel? Could be - snow is showing at the steepest parts of the bank. It's fascinating and too complicated for simple answers.
Thanks for the productive use of my time :-)
So there you have it!
