The movement of the rocks occurs when large, thin sheets of ice floating on an ephemeral winter pond break up in the sun.
So a small puddle forms in the shade, under the rock, which freezes and causes the rock to slide forward a little bit. Over time this scoots the rock across the ground and leaves a trail that looks like it was pushed but with no footprints nearby.
Very cool!
Not quite, to my understanding. Imagine a shallow pond that covers a rock maybe halfway up. The top of the pond freezes, forming a sheet of ice that’s attached to the equator of the rock and also floating on top of the liquid water underneath. Eventually this ice sheet breaks into pieces, and wind blows across the top of the ice. With enough surface area on the ice, the wind shear force on the ice is great enough to push the rock along the ground.
