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
Thousand Islands (Cocoa Beach) Several areas of the Thousand Islands were filled but not fully developed, leaving large areas of uplands. During the late 1960s Brevard County Mosquito Control began dredging the Thousand Islands south of Minutemen Causeway, resulting in conversion of salt marsh to upland dredge spoil with the state-owned C-34 impoundment. Native wetlands are dominated by red, black, and white mangroves. Succulent marsh contains saltwort, annual glasswort, perennial glasswort, sea blight, and shoreline seapurslane. The transition zone between salt marsh and upland is dominated by bushy seaside oxeye ("Borrichia frutescens" (L.) DC.) and buttonwood ("Conocarpus erectus" L.). Transition areas dominated by graminoid