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) deposit include the existence of a layer of plain sand (often containing terrestrial vegetation debris) sandwiched between sediments containing numerous small bivalve mollusc shells that are indicative of deposition in a normal lagoon environment. This uneven sand layer lacking shells suggests an interruption in the normal accretion of benthic sediments by a rapid deposition of dune material being washed in by severe wave action. There are about 100 islands in the Thousand Islands, The actual number of islands is meaningless due to the inundation of many areas during seasonal high water during summer. The relatively low topography and rising water