MONDAY MASHUP: Great Lakes tapestry map


This tapestry map is a combination of geology and topography. Photo: U.S.G.S.

The U.S. Geological Survey combined maps of geologic features (like rock types) and natural landscape features (like mountains) to make this tapestry map.

The combination more accurately reflects the surface of the earth, the age of the rocks beneath it and how the landscape was formed for the past 2.6 billion years, says the USGS website.

The colors represent the ages of the rocks. The hot pink covering most of northern Minnesota is rock from the Cambrian period about 500 to 550 million years ago. See the “color legend” for a complete key.

To get an idea of what’s beneath your feet, click “description of features” to read about some of the highlights in the Great Lakes basin.

Like the “Driftless Area” in Southwestern Wisconsin. The terrain there is rougher because it wasn’t scraped smooth by glaciers.

Wisconsin's "Driftless Area." Photo: USGS

In Michigan’s Lower Peninsula the ridges west of the “thumb” are glacial rubble piles, or moraines, of an extinct glacier.

Glacial debris west of the Michigan "Thumb." Photo: USGS

And check out the extinct Teays river in Ohio that was buried by glacial debris about 2 million years ago.

The extinct "Teays" river in Ohio shown in pink. Photo: USGS

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