It sounds like a metaphor but is geological reality: Washington, DC, is sinking. In fact, researchers led by a team at the University of Vermont predict that the ground will drop another six inches by the end of the century, reports UPI.

The cause isn't man-made: It's the result of an age-old geologic process that will continue to unfold for thousands of years. But it's presenting the DC region with a dangerous double-whammy—the ground is sinking at the same time that sea levels are rising because of warming temperatures, say the UV researchers.

The study confirms a long-held theory on why sea levels around DC are rising faster than any other stretch along the coast, reports the Washington Post.

“Right now is the time to start making preparations,” says lead study author Ben DeJong. “Six extra inches of water really matters in this part of the world." He and his team drilled dozens of boreholes around the Chesapeake Bay to figure out what's happening. The culprit is an ancient ice sheet that covered much of North America, then retreated, and the land is oh-so-slowly settling back into place. DC was actually in an area just outside the sheet and "bulged upward," as the Post puts it. "It's a bit like sitting on one side of a water bed filled with very thick honey," says DeJong. "Then the other side goes up.

But when you stand, the bulge comes down again." (In another geologic discovery, click to read why the Earth hums.)

This article originally appeared on Newser: DC Is Sinking, Literally

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