Technically called subsidence, this gradual settling or sudden sinking of Earth’s surface occurs when soft sediments shift, or loads bearing down on the ground push it deeper still. There are many causes, but the weight of cities themselves is rarely studied.
New York is sinking at a rate of 1-2 millimeters per year, the study found, under the weight of its sky-high buildings. A few millimeters might not sound like much, but some parts of the city are subsiding much faster, on par with the fastest observed rates at which tectonic plates rebound when glaciers melt…
In this new study, Parsons and colleagues calculated the cumulative mass of the more than 1 million buildings in New York City, which worked out to be 764,000,000,000 kilograms or 1.68 trillion pounds. Then they divvied up the city into a grid of 100-by-100-meter squares and converted building mass to downward pressure by factoring in gravity’s pull. Their estimates only include the mass of buildings and their contents, not the roads, sidewalks, bridges, railways, and other paved areas of New York City.
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