Strange-looking formations that resemble frozen lily pads have appeared this week on Scotland's River Dee, drawing Internet attention from around the world. Called "ice pancakes" or "pancake ice," the natural formations occur when conditions are just right.

The ice disks form when waves jostle pieces of smooth ice against each other, rounding their edges. As the resulting pancakes collide with the waves, they develop raised edges, making them look even more like lily pads.

Jamie Urquhart, a biologist with the River Dee Trust, recently noticed ice pancakes at Lummels Pool, a few miles downstream of Queen Elizabeth's summer residence at Balmoral. His photos are now making the rounds online.

What makes the pictures surprising is that pancake ice is most common