The natural diversity of the landscape supports over 1,200 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 inundated by the Champlain Sea. Many areas below this old shoreline are flat clay plains, with occasional outcrops of gneiss or limestone ridges.