The St. Lawrence River of eastern Canada flows northeastward for 744 miles, from the eastern end of Lake Ontario to the North Atlantic Ocean; however, the river's entire watershed is more than 2500 miles in length, from the streams of northeastern Minnesota through the Great Lakes and thence on to the Atlantic.
The basins of the Great Lakes were scooped out by the last of the Pleistocene Glaciers (the Wisconsin) as it plowed southward 70,000 years ago; as the ice began to retreat, the basins filled with meltwater and drained southward through the Mississippi River System. Once the glacier retreated farther into Canada, however, the Upper Midwest rebounded from its weight and, by about 12,000 years ago, the Great Lakes drained northeastward via the St. Lawrence River. Between Lake Ontario and Montreal, the young river's course is broken by numerous islands and rapids, forcing the construction of locks and channels to permit navigation from the Atlantic to the Great Lakes. Below the narrows at Quebec City, the St. Lawrence begins to widen and deepen, entering an ancient geologic graben in the Precambrian granite; the vast Canadian Shield, scoured by the Pleistocene glaciers, ends along the northern shore of the river's broad estuary while the Northern Appalachians curve in from the south, terminating as the core of the Gaspe Peninsula.
In the coming weeks, my wife and I plan to explore the valley of the St. Lawrence, from Montreal to the tip of the Gaspe Peninsula. We look forward to mild September weather, colorful autumn foliage, spectacular scenery and abundant wildlife (including, hopefully, a variety of whales in the Gulf of St. Lawrence). As an added benefit, I should get plenty of opportunities to practice my French. A plus tard!
