Thousand Islands - Frontenac Arch

The Thousand Islands – Frontenac Arch region or the Frontenac Axis is an exposed strip of Precambrian rock in Canada and the United States that links the Canadian Shield from Algonquin Park with the Adirondack Mountain region in New York, an extension of the Laurentian mountains of Québec. The Algonquin to Adirondacks region, which includes the Frontenac Axis or Arch, is a critical linkage for biodiversity and resilience, and one with important conservation potential. The axis separates the St. Lawrence Lowlands and the Great Lakes Lowlands. It has many distinctive plant and animal species. It 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.

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