Houses are so heavy that the whole city sinks

Under the enormous weight of New York's iconic skyscrapers, the city seems to be sinking a little deeper into the Earth each year.

A study published in Earth's Future shows that, in some areas of New York City (USA), the process of geological subsidence, sediment movement and settlement, is happening rapidly. In the most severe areas, it's now just sea level, like lower Manhattan.

Houses are so heavy that the whole city sinks Picture 1 Houses are so heavy that the whole city sinks Picture 1

According to researchers' estimates, 1,084,954 buildings across five New York boroughs weigh about 762 billion kilograms, equivalent to about 1.9 million Boeing 747-400s reaching their maximum payload.

New York is sinking one to two millimeters each year, the researchers say, even faster in the most severe areas. The lower the city, the more vulnerable it is to natural disasters like Hurricane Sandy in 2012. An estimated 8.4 million people in New York are in the vulnerable group of city flooding.

Houses are so heavy that the whole city sinks Picture 2 Houses are so heavy that the whole city sinks Picture 2

In addition to NYC, the US Geological Survey finds that sinking deeper each year is also happening in San Francisco.

Subsidence is common in developing coastal cities around the world. People in these cities will face sea level rise four times faster than in other regions.

Finding ways to mitigate the growing flood risk in cities is a common challenge globally.