Manitoba has been subjected to glaciation many times in the past. The most recent of these glaciations, which began about 75,000 years ago and ended in Manitoba about 8,000 years ago, was largely responsible for our present day landscape. The province was covered by a 2 kilometer high sheet of ice which finally began to melt back about 18,000 years ago. The great weight of the ice sheet caused the surface of the land to be depressed at least 600 meters.

GLACIER EFFECTS
As the glacier moved across the land, loose material on the surface (soil, sand, gravel etc.) was frozen into the bottom of the glacier. The moving ice and incorporated debris scoured the solid rock surface leaving scratches and grooves still visible today.

When the margin of the ice sheet began to melt, debris that was frozen into the ice many miles to the north was dumped at the edge of the glacier. It gradually accumulated as a ridge called an end moraine. The Pembina Mountains are an example of a group of end moraines.

Instead of gradually retreating northward as the climate warmed, much of the ice over Manitoba stopped moving completely and melted in place. Such a glacier is known as a dead or stagnant glacier. As the glacier melted, debris accumulated on top. When the ice finally melted away the landscape became characterized by small hills and depressions typical of the area west of Morden.

LAKE AGASSIZ
One of the most important effects of glaciation on Manitoba was the formation of Lake Agassiz during the Quaternary period. The deposits of silt and clay left on the bottom of the lake account for the rich farmland of the Red River Valley.

Lake Agassiz was formed as north flowing rivers were dammed by the ice sheet preventing the water from draining into Hudson Bay. The lake was constantly changing its size, shape, and depth as the glacier’s edge fluctuated. Along the Manitoba Escarpment beaches of fine sand indicated various levels of the lake.