Two photos, one question

Little Springtime works at the media lab at her university. They have a 3D printer, which, from next semester (... I think?) will be available to students to use. She tested it out and made a hedgehog.



Yesterday and today have been cold, with magnificent if somewhat ominous high winds, but the day before yesterday was warm and melty. Melted snow was coursing down the road. Or rather, it was lapping down the road.

Why does it go down the road in ripples like this? (See the smiles, one after the...