NATURAL HISTORY, TORONTO REGION
The region is not one of high relief, the most elevated points to the south not exceeding 850 feet and to the east or north within 100 miles probably not going beyond 1,200. The highest point in the peninsula between the Great Lakes rises to something over 1,700 feet near Dundalk, 76 miles northwest of Toronto. Lake Ontario is 246 feet above the sea, Lake Erie 572 feet and Lake Huron 581.
Although the variations in elevation are moderate there is great variety of surface features, including gently sloping lacustrine plains, rolling uplands, and an escarpment which crosses the region from south to north with a sudden rise of 300 or 400 feet. It has adjoining it some of the greatest lakes in the world, as well as many smaller bodies of water, and it is well watered with streams of every dimension up to Niagara River, some, like the Thames or Grand River, with gentle, meandering flow, and others with rapids or waterfalls having a sheer leap of 160 feet.
Except in the Archaean portion to the north the rocky structure is uniform and undisturbed, the beds of sedimentary rocks dipping very gently to the southwest without folds or faults or interruptions by eruptive rocks.
From middle Palaeozoic times to the present, so far as known, the region has been dry land except where lakes have covered it owing to Pleistocene shiftings of level or to the damming of valleys by ice masses. The most dramatic episodes in its history are the advances and retreats of the continental ice