Oh, it's just the isostatic rebound

Tom Jackson
Mar 23, 2010

Here's an odd term I learned over the weekend -- isostatic rebound -- that describes a a really odd geologic phenomena I never heard of before. Have you felt the earth moving slowly under your feet?

The glaciers in Ohio and the Great Lakes region have been gone for 10,000 years, but when they left as the earth warmed up, a heavy load of ice that was weighing down the earth's crust was removed. And ever since, little by little, the surface of the earth has been rising in reaction to all of that load being removed. In other words, in certain sections the earth was depressed by the ice. Hey, I'd be depressed, too, if I had a big block of ice sitting on me.

Just to make things a little more confusing, there are places where isostatic rebound is causing the earth to sink. In places next to the ice, the pressure of the glaciers caused the earth to smoosh up, kind of like when you drop a rock in a mud puddle and the mud rises around the rock. Now that the glaciers are gone, that land is sinking down. "Smoosh up" may not be the correct geologic term, but it's what makes sense. This was explained to us by Frank Quinn, a retired hydrologist with the National Oceanic and Atmospheric Administration, did his best to explain this to us.

Try to use "isostatic rebound" in casual conversation. You'll sound smart.