Have you ever seen an ice spike? They occur sometimes when the surface of a body of water freezes quickly. When the water below the surface freezes, it expands and forces itself out through cracks in the surface.
Last night it got really cold here. Look what I found in the bird bath this morning.
That’s more than 2” tall. I think that it’s the biggest one I’ve ever seen! And look at the shape. It’s a lot wider at the top than at the bottom. Usually they’re very pointy. The internal structure is pretty interesting too.
If you like this sort of thing, you might be interested in Dr. James R Carter’s website about interesting ice formations.