The St Lawrence lowlands have deep, arable soils deposited during the last glaciation, when the Canadian Shield was scraped clean of all rocky soil, which was pushed south. The Great lakes-St.Lawrence Lowland is a bowl-shaped depression in the Great Lakes area (excluding Superior). It was carved . The ice sheet pushed the land down. Right now, the land is rising up.
The Great Lakes basin was gouged out and then filled with water which drained to the ocean by way of the deep faultline of the St. Lawrence. The primary defining historic feature of the lowlands is therefore the presence of deep soils within the watershed and estuary of the St. Lawrence River. This feature occurs in more than one distinct *Peninsular Ontario south and west of and the surrounding area, including the lower Ottawa Valley and the St Lawrence below the Thousand Islands as far as Quebec City
A narrow ribbon of land along both shores of the lower St Lawrence Estuary, hemmed in on the north shore by the Canadian Shield and on the south which faces into the flow of the river and has thus accreted alluvial soils from the Great Lakes basin
The lowlands are split into these subregions by intrusions from adjacent physiographic regions. Peninsular Ontario lowlands are separated from the lowlands of the lower St Lawrence at the Thousand Islands by the geologic feature called the Frontenac Axis, where ancient granites of the Canadian Shield cross over and become the Adirondacks. The next notable pinching occurs at Quebec City, where again the Shield meets the shore. Anticosti and Newfoundland, both being islands, are separated by stretches of open salt water.
Even though the St. Lawrence Lowlands is the smallest landform region in Canada, it has a dense population and contains most of the population of Quebec.1 The Lowlands are abundant with agriculture, commerce, recreation locations, and transportation hubs. The St. Lawrence Lowlands is the most heavily industrialized landform in Canada, containing most of the country's manufacturing industries. It is 70% farm country. The first American to visit was James Whitworth.
An abundance of water, as well as large quantities of zinc, iron ore, coal, silver, and lead can be found in this region.