The Daily Parker

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Chicago's sinking, but don't worry

Wherever a landmass had several kilometers of ice on top, it deformed. Glaciers covered much of North America only 10,000 years ago. Since they retreated (incidentally forming the Great Lakes and creating just about all the topography in Northern Illinois), the Earth's crust has popped back like a waterbed.

Not quickly, however.

But in the last century, Chicago has dropped about 10 cm while areas of Canada have popped up about the same amount:

In the northern United States and Canada, areas that once were depressed under the tremendous weight of a massive ice sheet are springing back up while others are sinking. The Chicago area and parts of southern Lake Michigan, where glaciers disappeared 10,000 years ago, are sinking about 10 to 20 cm each century.

One or 2 millimeters a year might not seem like a lot, but “over a decade that’s a centimeter. Over 50 years, now, you’re talking several inches,” said Daniel Roman, chief geodesist with the National Oceanic and Atmospheric Administration. “It’s a slow process, but it’s a persistent one.”

While Chicago’s dipping is gradual, this dynamic could eventually redefine flood plains and work against household sewer pipes that slope downward to the sewer main.

The same phenomenon has affected the UK as well. Scotland is popping up and England is sinking, as are other pairs of regions similarly glaciated. (Sterling, however, has a long way to go...)

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