Further south (say, Mason, Oceana, Muskegon counties) on Lake Michigan, we used to see “mortars” and “cannonballs” form. As in the paper on Lake Superior icefoots, a good cold winter would leave the inshore area iced over; sometimes the ridge-and-plain ice would extend out half a mile. At the seaward edge of this ice, wave action would start piling up slabs and eventually one of the slabs would tilt forward/shoreward. Smaller chunks (cubic half-yard or so) would be slapped up against the tilted slab by waves. With luck, a channel would form, and the chunk would be delivered to the same point on the slab, again and again.
Over the course of a day or two, the wave-slapping action would tumble the chunk into a spherical form. At the same time, the slab would begin to develop a hole where it was being pummeled by the chunk. If the wave action held steady, there would eventually be a great moment where the newly-formed cannonball would pop through the mortar-tube worn into the slab – big excitement!
I said “used to see” because it’s been 20 years since winter was cold enough to sustain well-packed inshore ice ::sigh:: And lest you think us hicks spent entire days doing nothing but smokin’ down and watching a cannonball form, observation periods were punctuated by recreation…dragging some plywood out onto the moonlit ice and firing up the grill. Or taking a coal shovel up to the top of a frozen, bare-faced dune, seating yourself with handle between legs, saying a quick prayer while pushing off, and letting gravity have its way. (Bog, I miss being young ; - )
