Think of Earth as a rubber ball. If you push in at one place, the surface will indent. Surrounding that indentation, the ball will bulge outward.

Near the end of the last Ice Age, just 20,000 years ago, continental ice sheets covered 25 percent of Earth’s landmass, pushing down on Earth’s surface with as much as 150 tons per square foot of pressure.

This depressed the surface and pushed up the land around the perimeter.

During the last 15,000 years, the Ice Age ended and glaciers have naturally retreated to cover only 11 percent of the land surface today.

And just like a rubber ball, the Earth’s surface has been rebounding—very slowly.

Areas that were depressed by ice are rising. Canada, Scotland, and Scandinavia all have risen 4 to 6 inches over the past century.

Areas that had bulged outward at the edge of glaciers are now sinking, back to pre–Ice Age levels, around 4 inches per century.

This can be seen in southern England and Ireland and the northern and middle U.S., including many cities like Chicago, Milwaukee, and Cleveland.

In low-lying near-coastal cities like London and Washington, D.C., falling land levels combined with rising seas from continued glacial melt are making those cities more prone to flooding.

We can expect rising and falling landmasses, and associated shoreline changes, as Earth continues its slow motion Ice Age rebound.