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
Islands in the River Thames or more artificial lock islands separating the lock from the weirs. These may have been created by building an artificial island in the river or by digging an artificial canal to contain the lock and turning the land between that and the river into an island. In many cases the lock island contains the lock keeper's house and can be accessed across the lock gates. Such lock islands are only listed above if they have a specific name of their own: all Thames locks are listed in Locks on the River Thames. Islands in the River Thames This article lists