How the shape of our land shaped the way we live, an example in Minnesota

Minnesota winters are infamous, but ice and snow affected more than just the local culture. They also shaped the very ground on which the Twin Cities are built. The glacial history of the Twin Cities metro, 10,000 years old, can disappear beneath the carpet of roads and buildings covering the region. But a relief map showing the region’s topography leaves the glaciers’ fingerprints plain as day.

The Twin Cities terrain is shaped primarily by glaciers, both directly and indirectly. The area’s hills are largely glacial moraines — piles of sediment hundreds of feet high, bulldozed by advancing glaciers in the last ice age roughly 10,000 years ago.

Glaciers also explain why the Minnesota River’s valley is so much bigger and deeper than the Mississippi River’s, even though today the Mississippi is the much larger river.

One glacier melted into Lake Agassiz, “one of the largest, if not the largest, lakes in world history” in what is now the Red River Valley along the border with North Dakota. When that lake burst over the continental divide at Traverse Gap, a gushing torrent of water called Glacial River Warren carved a deep valley across the state from about 11,700 years ago to 9,400 years ago.

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