A new study looked into the geology underneath the New York City and compared it with data from satellites to reveal the collapse of its footprint. Doing so enabled researchers to see that the Big Apple is sinking and that the weight of its enormous skyscrapers plays a significant role in this.
Subsidence
According to Science Alert, this is technically referred to as subsidence, which is the gradual or sudden sinking or settling of the earth's surface when loads push the ground down or soft sediments shift.
The National Oceanic and Atmospheric Administration also notes that subsidence is typically caused by natural gas, oil, water, or mineral sources being removed from the ground through mining, fracking, or pumping. It may also result from erosion, soil compaction, earthquakes, sinkhole formation, glacial isostatic adjustment, and water additions to fine soils that wind deposited.
Now, while there are many causes behind such a phenomenon, city weight is rarely a subject of study.
New York City Sinking?
The study published in Earth's Future found that the city is sinking at a rate of 1-2 millimeters per year. This is considerably due to the weight of its high-rise structures. Though these few millimeters may sound meager, some areas across New York City have faster subsidence rates, as noted by Science Alert.
This is quite bad news for the Big Apple, which houses over 8 million individuals. Hence, the study suggests that further efforts must be exerted to counter the rising sea levels and growing flood risks. However, adding huge sea walls may not be the right answer to this.
The researchers explain that the point of the study is to raise awareness regarding how each high-rise building erected at lakefront, riverfront, or coastal locations may affect future flood risk.
The findings also shed light on human construction in totality. Science Alert reports that, as of 2020, specialists estimated that every man-made thing nearly or already outweighs the dry weight of every last living creature on the Earth. Roads and buildings outweigh shrubs and trees altogether, while plastics end up doubling animal weight.
For this study, Tom Parsons, a geologist from the United States Geological Survey, and colleagues from the University of Rhode Island calculated the cumulative mass of over a million buildings all over New York City. The total weight was found to be equivalent to 1.68 billion pounds, or 764,000,000,000 kilograms.
They divided city areas into 100-by-100-meter square grids and converted the building mass into downward pressure. They did so by considering the pull of gravity, as reported by Science Alert.
Findings only cover building and content mass, roads, bridges, railways, and sidewalks; other paved sites across New York City were all excluded.
Despite these limitations, the findings sharpen earlier observations of subsidence in New York City by considering the complicated geology under the city. These mainly consist of clay lake deposits, silt, sand, and bedrock outcrops.
By modeling substrate behavior, the authors demonstrated that artificial fill and clay-rich soils are vulnerable to subsidence. Though more elastic soils end up bouncing back post-construction, bedrock, which anchors several skyscrapers, does not budge in the same way.
The researchers then compared their models with data from satellites that looked at the height of the land surface. With this, the researchers warn that growing urbanization, such as pumping and draining groundwater, may only make the subsidence problem in New York City worse.
There are also studies that have found subsidence to be a problem in other coastal cities, such as Jakarta. Now, though an extraordinary number of high-rise buildings have already been constructed, the future of the Earth is still not definitive. Science Alert notes that decreasing greenhouse gas emissions is the best method available for combating such future risks.
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