Manitoulin Island and the Bruce Peninusla are both made of Niagara limestone; geologically, they are both parts of the Niagara Escarpment, the same formation that Niagara Falls (and Chittenango Falls) goes over. It's a thick layer of whitish stone lying nearly horizontal, the remnant of an ancient sea that covered the area for a long time. This beach is just a little north and east of the ferry terminus.