How the Last Ice Age Reshaped Earth's Geography

The Last Glacial Maximum (~26,000–19,000 years ago) and subsequent deglaciation sculpted the modern world in six profound ways:

1. Sea Level Drop (~120 m / 400 ft): Exposed continental shelves—Bering Land Bridge (Asia–America migration), Sundaland (SE Asia), Doggerland (UK–Europe). Coastlines shifted dramatically.
2. Ice Sheet Sculpting: Laurentide (N. America), Fennoscandian (Europe) sheets carved fjords (Norway, NZ, Chile), U-shaped valleys, cirques, arêtes, moraines, drumlins, eskers, kettle lakes. Great Lakes basins = ice-scoured depressions filled by meltwater.
3. River & Lake Reorganization: Meltwater floods (Missoula Floods, Lake Agassiz outbursts) created Channeled Scablands, Mississippi drainage, St. Lawrence route. Isostatic rebound still tilting Great Lakes.
4. Vegetation Shifts: Tundra/steppe replaced forests at mid-latitudes; refugia preserved biodiversity. Post-glacial forest migration northward ongoing.
5. Habitat Fragmentation & Speciation: Ice barriers isolated populations—e.g., polar bear evolution from brown bears, distinct fish lineages in unglaciated refugia.
6. Permafrost Legacy: Continuous permafrost in Siberia, N. Canada, Alaska—thawing now releases methane, destabilizes infrastructure.

Every major northern landscape—from Manhattan's bedrock to the Fertile Crescent's soils—bears the ice age's signature. We live in its deglaciation echo.