The Laurentide Ice Sheet was a massive ice formation that covered much of Canada and parts of the northern United States during the last Ice Age, approximately 26,000 years ago. It played a significant role in shaping the landscape, carving out valleys and creating features like the Great Lakes. As the climate warmed, the ice sheet began to melt around 14,000 years ago, leading to rising sea levels and changes in ecosystems. The melting of the Laurentide Ice Sheet contributed to the formation of various landforms and influenced the distribution of flora and fauna in the region, marking a significant transition in Earth's geological history.