Sinking Cities

All over the world people are moving into cities, and as cities get more densely populated, they get heavier and sink into the Earth. Jakarta, Lagos, Tehran, Mexico City and Houston are just a few of the global cities known to be sinking at a rate that is a problem now or could be soon. Geophysicist Tom Parsons at the US Geological Survey recently took a stab at estimating how fast a city might sink.