Snow Rollers

I recently presented a session on teaching electricity at the Utah Science Teachers Association Conference. On my way home, I did quite a bit of photography of the snowy landscape, but one roadside slope caught my eye. Driving past, I saw something that I had only seen in books, and a few recent weather articles. Snow rollers! They are usually quite rare, and of the hundreds of snowy road cuts that I passed on the drive home, this was the only one that had them.

What makes snow rollers so rare? Each roller is a coil of snow, wound up like a cinnamon roll. For that to happen, you need the following conditions.

  1. A bottom layer of ice or hard snow crust.
  2. A thin, top layer of wet snow that is just below the freezing point.
  3. A slope that is not too steep or too gentle.
  4. Wind blowing from the right direction.

Lets look more closely at a snow roller, and find out how it forms.

The combination of wind and slope starts the process by causing a small clump of snow to roll. If the slope is gentle, it takes a stronger wind. If the slope is steep, like this one was, a gentle breeze can be enough. As the clump of snow rolls, the thin layer of wet snow sticks to it. Because there is a layer of ice underneath, that snow comes away easily, without providing enough friction to stop the roller. As it continues to roll, it keeps adding more wet snow to the coil.

The farther it rolls, the larger the coil gets. At this site, the smallest were only about an inch across. The largest that I saw was about eight inches across.

You can see the thickness of the wet snow layer by looking at the thickness of the coils on each roller. Here, the layer was about 1/4 of an inch thick.

As they reached the bottom of the slope, the wet snow was deeper. That created enough friction to stop them. If the slope had been longer, they could have grown much larger.

I had a marvelous time photographing them. I am sure that the people who drove past wondered why that crazy old man was crawling around on his hands and knees in the slush, taking pictures of a pile of snow. The science educator in me kept hoping that someone would stop to find out, but they all zipped on by. They will probably never know what a wonder-filled experience they missed.

brevard wrote on Thu, 02/27/2014 - 10:51:

I love the pics. You are sooooooooooooo cool

pecangrove wrote on Mon, 02/24/2014 - 13:18:

pretty cool

peanutkids2 wrote on Wed, 02/19/2014 - 13:36:

We don't have any snow here right now. Before you showed me these rollers, I had no idea what they were! -Peanut2

I thought it was really cool! Thank you for stopping on the side of the road to take those pictures. -Peanut1

Lol! We would have stopped to ask you what on earth you were doing. And then we would have talked your ear off. So, be glad we didn't pass you by! Thank you, this is awesome! -TeacherMom

homesoulky wrote on Mon, 02/17/2014 - 22:00:

Mr. Krampf,
Thank you for sharing this experience!

Londonsje wrote on Thu, 02/13/2014 - 21:24:

What are rollers?
I can tell there really cool!!!!

USTA (not verified) wrote on Sat, 02/15/2014 - 15:49:

Where in Utah did you find these? I live in Utah and would love to go see them in person! Thanks for coming to present at USTA, you were fantastic!

rkrampf wrote on Sat, 02/15/2014 - 18:43:

I found them on Highway 89, north of Kanab. They were on the west side of the road at the sign for Alton, but they have likely melted by now.

I had a marvelous time at USTA, and hope to be back next year.