This photo, taken Jan. 25 at the Albany Dam over the Sugar River in Albany, Wis., show a sizeable floe of foam that was likely caused by phosphorous and other chemical run-off, said Allen Penticoff, a member of the Decatur Lake Mill Race Association and Rock River Times columnist.

In an email, Penticoff wrote that the foam appeared to be at least eight feet thick, and seemed to have been “formed by a thin ice shelf skimming the foam bubbles off the river, then packing them up.” The sight is reportedly not a strange one in Albany, and often times, chunks of foam break loose and float through town.