The ground is slowly sinking or deforming beneath all the biggest cities in the US, according to new satellite analysis. If cities don't do something about this land-sinking phenomenon, called subsidence,

A new study of the 28 most populous U.S. cities finds that all are sinking to one degree or another. The cities include not just those on the coasts, where relative sea level is a concern, but many in the interior.

At least 65 percent of urban areas in 25 major cities are sinking, with some local spots dropping by about two inches a year, new research has shown.