Paleontology and geology
At various times in the Quaternary, Manitoba was covered by tundra, forest, and sheets of ice several kilometers thick. The glaciers scraped the bedrock, smoothing and flattening the surface. They picked up sediment as they moved and re-deposited it as they melted in the form of low hills called moraines. Some areas preserve layers of sediments from multiple glacial episodes. After the last glaciation, ice blocked the flow of the melting water, forming a large lake called Lake Agassiz, which covered most of Manitoba. The large ridges of sand and gravel found in the south represent shorelines of this ancient lake. Giant beaver, mammoth, mastodon, muskox, giant short-faced bear, and giant ground sloth lived on the tundra and in forests around the lake. Within the lake, many different mollusks and fish could be found, including sturgeon. As the ice continued to melt and the crust rebounded from the released weight of the glacier, the water drained away. Today’s Lakes Manitoba, Winnipeg, and Winnepegosis are remnants of this giant lake.