Thousand Islands – Frontenac Arch is one of four ecoregions of the Mixedwood Plains. The Thousand Islands in the Saint Lawrence River have a distinctive flora and fauna and are a part of the biological corridor. The bedrock is mostly gneiss, granite and marble, more than a billion years old. The Frontenac terrain is the youngest of the Ontario portions of the arch, dated at 1.2 billion years old. These rocks were once part of a large mountain chain of the ancient supercontinent of Rodinia. There is also a meteor crater near Holleford, where the shield meets the limestone plains of southeastern Ontario. The area
Ten Thousand Islands at the northern end of the Ten Thousand Islands was occupied year-round 3,500 years ago, and other sites are presumed to have been inundated by a rise in sea level. The material culture of the Indians living in the Ten Thousand Islands was distinctive enough to be classified as, at least, a sub-area of the Glades culture area. Almost all of the Ten Thousand Islands are currently uninhabited. The largest, Chokoloskee Island, which is connected to Everglades City by a causeway, has about 400 permanent residents. Other islands have been sporadically inhabited in the 19th and 20th centuries by individuals