Continental Uplift Created two Countries

The Great Lakes are a natural boundary between the United States and Canada. The manmade lines to the east and west are extensions of the watery wedge that thrusts almost halfway across the continent. And the economies of New England and New France, the forerunners of today's two countries, centred around two river systems: the Hudson and the Saint Lawrence.

The forces that created these rivers and the lakes behind them, and the point at which these took their shape are defining moments par excellence. The melting of the glaciers and the rising of the land that accompanied this led to three distinctly different orientations of the continent.

The first was due south. Meltwater from an enormous continental ice sheet flowed through what is now the Mississippi basin with a far bigger drainage area. Had that continued, North America would be one country around the delta, or two countries, east and west, on river opposite banks.

The second phase occurred when the Lakes Erie and Ontario, larger than today's lakes, drained eastward through the Hudson-Mohawk System. This was caused by uplift that cut off the southward drainage path to the Mississippi. The upper Great Lakes--Superior, Michigan and Huron--drained through what is now Georgian Bay, Lake Nippigon and the Ottawa River.

Had this pattern continued the American colonies would have had a route to the interior like New France did. The pressure for land that contributed to the American Revolution would not have been as acute, as settlers would not have had to cross the mountains to move inland. The Saint Lawrence-Ottawa would have been a more northerly system, like today's Mackenzie.

This landscape would have favoured two separate Americas as later emerged in the Civil War. Canada, if it had emerged as a country at all, would have consisted mainly of Arctic and sub-arctic territories. Like Greenland, it might have remained a European colony for much longer.

The third phase began when out Hudson outlet to the lower Great Lakes closed off, forcing them to drain up what is now the Upper Saint Lawrence Valley. At about the same time, the upper Great Lakes cut through an isthmus to drain through the lower ones.

This expanded a small cataract into the mighty Niagara Falls and swelled the Saint Lawrence even further as it made the Great Lakes into a single drainage system instead of two. French domination of this system, building forts down the Mississippi, created a counterweight to English power in North America.

Even though the Mississippi extension was later lost to the US, the French base was sufficient for two countries on the continent, rather than one. It was French voyageurs who continued to sail west from the Great Lakes, whose waterways became the routes of the later railways that secured Canada as an east-west power parallel to the United States.

Niagara Falls is a highlight for visitors to both countries, each of which has a falls--or half of the Falls to call its own. The Niagara River is part of the natural border between Canada and the US. And ths natural history of the River and its Falls--which have changed considerably in the last 10,000 years--mirrors the changing face of the content, and shows us what might have been.