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
North American river otter intermediate in salt marshes, and highest in swamp forests. During the dry season, they will recede from the marshland and move to permanent ponds, where water is available and food is in greater supply. In Idaho and Massachusetts, ecological elements preferred for latrine sites include large conifers, points of land, beaver bank dens and lodges, isthmuses, mouths of permanent streams, or any object that protrudes from the water. North American river otters often reside in beaver ponds. Encounters between North American river otters and beavers are not necessarily hostile. In Idaho, North American river otters and beavers were recorded in