Why Winnipeg's Soil is the Way It Is

Winnipeg, a city with rich geological history, sits on land that was once the bottom of the vast glacial Lake Agassiz. This ancient lake, formed during the last Ice Age, has left a lasting legacy on the region's soil composition, significantly influencing modern construction, from roadways to patios.

Laurentide Ice Sheet

Until about 10,000 years ago, a massive sheet of ice covered most of Canada and a large portion of the northern United States – millions of square kilometers.

We have all heard that glaciers move (at a glacial pace, of course!). As the ice shifted, it ground down the rock below. This process created fine particles that would eventually make up the clay we have today.

The Geological History of Lake Agassiz

After the glaciers began to melt, a massive glacial lake, Lake Agassiz, formed.

Lake Agassiz, one of the largest glacial lakes known to have existed, covered much of Manitoba, northwestern Ontario, and parts of North Dakota and Minnesota. It formed about 13,000 years ago as the Laurentide Ice Sheet began to melt. The lake's sheer size and the duration it existed (several thousand years) meant that it had a substantial impact on the landscape.

The sediments from the glaciers settled at the bottom of Lake Agassiz.

Once Lake Agassiz drained, the clay sediments remained. Over time, they were compacted and formed the clay-rich soil that is characteristic of the region today. This clay, known as Red River clay, is characterized by its fine particles and high water retention capacity.

Implications for landscapers

Unfortunately, high water retention means Manitoba's clay soils can shift dramatically. The soil will expand during a wet spring, and then contract during a hot, dry summer. As a Winnipeg landscaping company with 26 years of experience, we have refined our patio construction methods and have found ways to mitigate this instability, building patios that will stand strong for many years.