| Vegetation: |
Thorah Island is a mixture of farm, woodland, swamp and marsh. The island shows some similarity to Georgina Island with respect to physical and vegetative characteristics. Numerous outcrops of bedrock appear in the form of Ordivician limestone, principally near the shore. The interior consists of cleared fields interspersed with shrubby second growth ash and poplar. Most fields appear to have been abandoned for at least a decade, indicated by a dense cover of asters, grasses, sumac and other shrubs.
The largest single natural area on the island covers the entire southwest corner. It is an area of swamp forest, dense shrubs, old fields and shoreline. Sand beach is present along the west side, while the opposite shore is an extremely narrow strip of tangled vines, willows and shrubs. Bulrushes parallel the latter shoreline, creating waterfowl breeding habitat. [Ecologistics Limited 1982]
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| Landform: |
The Thorah Island E.S.A. lies in a depressional feature within the Limestone Plains Physiographic Unit. The soils found here are very poorly drained organics that fall under the general heading of Muck (Olding eT AL., 1956). They are comprised primarily of well decomposed organic materials and the water table here is at or near the surface throughout much of the year.
The northern portion of Thorah Island (not included in the E.S.A.) is composed of limestone bedrock with a thin layer of soil developed from glacial till. The depth of the soil layer and, therefore the drainage, is variable; topography is generally level to very gently sloping.
The shallow water shoal zone along the western end of the north shore, and the west shore to South Point are of significance for fish spawning. Water depths here range from 1 - 5 m. Both limestone rock of diameter 15 - 30 cm and sand occur on the lake bottom in this area. The zone of significance varies in width from 0.2 km to 1.5 km, being widest off Eagle Point and South Point. [Ecologistics Limited 1982]
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