Lanark County - Geography

Geography

According to Statistics Canada, the county has a total area of 3,033.82 square kilometres (1,171.36 sq mi). It is located in the subregion of Southern Ontario named Eastern Ontario. Geologically, the northern part of the county is in the Canadian Shield and the southern part is in the Great Lakes Basin. The county has two large rivers, the Mississippi and Rideau, each of which empty into the Ottawa River. The landscape is varied including Canadian Shield (with gneiss, granite and marble) as well as limestone plains, with a variety of tills, sands and clays left from the melting of glaciers in the last ice age.

At the time of settlement, most of the county was covered in temperate deciduous forest; the dominant forest trees included maple, hemlock, oak and beech. Some of the higher ridges in the west of the county were likely once natural fire barrens, with a distinctive fauna and flora. The clearance of forests began with early settlement, at which time one of the important exports from the area was potash, made from the ashes of the trees burned in clearing.

The natural diversity of the landscape supports over 1200 species of plants in the county flora. Seventeen areas have been documented as outstanding examples of plant diversity; these include Blueberry Mountain, Burnt Lands Alvar, Clay Bank Alvar, Christie Lake, Murphy's Point Provincial Park and Almonte Town Park. The county also has 47 provincially significant wetlands. Some of the largest are Blueberry Marsh (north of Perth), the Innisville Wetlands (upstream of Mississippi Lake) and the Goodwood Marsh south of Carleton Place. In addition to David White's list of 17 areas of plant diversity, Paul Keddy lists 17 special places in the county. Both lists have the Burnt Lands Alvar, the Christie Lake Barrens and Murphy's Point Provincial Park. Keddy's list adds areas such as Playfairville Rapids, Lavant/Darling Spillway and the Carleton Place Hackberry stand. Also of interest is an old shoreline which crosses the county diagonally, approximately from Almonte in the northeast to Perth in the southwest. This shoreline was formed about 12,000 years ago near the end of the last ice age when much of the Ottawa Valley was innundated by the Champlain Sea. Many areas below this old shoreline are flat clay plains, with occasional outcrops of gneiss or limestone ridges.

Some of the distinctive southern animals in the county include five-lined skinks (Ontario's only species of lizard), black rat snakes and southern flying squirrels. Unusual southern plants include the Arrow arum, a nationally rare wetland plant found near Mississippi Lake. The south-facing cliffs over Big Rideau Lake, including Foley Mountain, have a slightly warmer climate, and therefore support an unusual southern flora including shagbark hickory, tall cinquefoil (Potentilla arguta) and a rare fern, blunt-lobed woodsia . Cliff Bennett provides a list of 26 routes for canoe and kayak exploration of the county .