"These are impact craters in the Canadian Shield, the oldest continental crust of the North American plate. Because it’s been tectonically inactive for a long time and continental glaciers removed most of the topsoil, many craters are visible. This lake is called Lac a l’Eau Claire. There is a lot of evidence that the lake is formed by 2 impact craters. It was originally thought that the 2 impacts were formed at the same time by an asteroid that split or was a binary asteroid. There is some very compelling evidence that these are 2 different impacts, ~200 million years apart. It might seem like a million to one shot that 2 impacts could be so close, but we see many overlapping craters on other planets. The low probability thing for me is that the craters were both preserved and exposed."