Built by a geologist
The Laurentide Ice Sheet
The Laurentide Ice Sheet The Laurentide Ice Sheet was one of the most massive features in Earth's recent geological history. At its maximum extent during the Last Glacial Maximum 26,000–19,000 years ago , it was one of the largest ice sheets ever to exist. Scale and Dimensions The Laurentide Ice Sheet was staggering in scale: - Area : 13.4 million km² larger than Antarctica today - Thickness : Up to 3–4 km thick over Hudson Bay - Volume : Enough ice to lower global sea levels by approximately 70 metres - Weight : So heavy it depressed the Earth's crust by hundreds of metres Extent The ice sheet covered: - Virtually all of Canada east of the Rocky Mountains - The Great Lakes region of the United States - Parts of the northern Great Plains states - New England and New York At its maximum, the southern margin reached as far south as modern-day New York City , Chicago , and St. Louis . Formation and Growth The Laurentide Ice Sheet formed through the gradual accumulation of snow that compacted into glacial ice. Key factors: 1. Orbital cycles Milankovitch cycles reduced summer temperatures enough that winter snow didn't fully melt 2. Snow accumulation over thousands of years compressed into dense glacial ice 3. Ice flowed outward under its own weight , like a very slow-moving fluid 4. Multiple ice domes formed — the largest centred over Hudson Bay Effects on the Landscape The ice sheet profoundly reshaped Canada's landscape: - Erosion : Scraped and scoured the Canadian Shield, creating the characteristic rocky, lake-dotted terrain - Deposition : Left behind enormous quantities of glacial sediment till, moraines, outwash - Drainage : Completely reorganised Canada's river systems and drainage patterns - Lakes : Created thousands of lakes, including the Great Lakes - Crustal depression : Pushed the Earth's crust down by hundreds of metres Retreat and Disappearance The Laurentide Ice Sheet began retreating approximately 19,000 years ago as global temperatures rose: - Retreat was not steady — there were periods of re-advance - Glacial Lake Agassiz formed as meltwater pooled along the retreating ice margin - The last remnants of the ice sheet disappeared from northern Quebec approximately 6,500 years ago - The ice sheet's meltwater contributed to sea level rise of 70 metres Legacy Even though the ice sheet is gone, its effects are still felt today: - Isostatic rebound —