In every city studied, at least 20% of the urban area is sinking – and in 25 of 28 cities, at least 65% is sinking. The nation's biggest cities are sinking, according to data from a new study.

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