Okay kiddo, imagine a really big bowl filled with water that is so cold it's frozen. That's what a glacier is, it's like a big block of ice sitting on top of a mountain. But a long, long time ago, there was a glacier in Canada called the Laurentide Ice Sheet, and it covered a lot of land.
This big glacier was so heavy that it pushed down on the ground and made a huge hole in the earth. When the climate got warmer and the glacier started to melt, the water filled up that hole and that's how Glacial Lake Ojibway was formed.
The lake was really big, like the size of some states in the USA. It was nearly 2,000 feet deep, which is higher than the tallest buildings in most cities! Because it was so deep, the water was really cold and clear.
Now, as the glacier continued to melt, the water from Glacial Lake Ojibway rushed out and carved out new paths for rivers to flow through. Eventually, the lake emptied out completely and there were only smaller lakes left. Some of those smaller lakes still exist today, like Lake Winnipeg, Lake Superior, and Lake Michigan.
So that's the story of Glacial Lake Ojibway, a really, really big lake that was formed a long time ago and shaped our geography today!