Lack of snow cover/insulation, allows seeping water to freeze creating a dam until the water flows over the top, freezing, creating a higher dam, and a repeat until the "glacier" gets 1,2,3,4,etc., feet thick. Especially a problem on mountain roads. Glaciation can also be a problem on creeks and smaller rivers.
That’s an interesting lesson. Thanks Wolf
Thanks Connie for asking about it.