San Francisco, as well as other large cities in the SF Bay Area, are falling about a half-inch closer to the earth’s core each year.
Cities weigh a lot … like, an unfathomable amount. For a city of 2,000, engineers and geologists estimate those people and the infrastructure they need collectively weigh about 600,000,000 lbs. While it’s not exactly a one-for-one extrapolated estimate, San Francisco — a city of over 800,000 year-round residents – would weigh 400 times more than that previous figure. San Francisco’s density also means that mass is concentrated; outside of New York City, San Francisco is the second-densest city in America; SF is also among the few metros in the country that sits as an example of theme park urbanism, because of that density.
Anyone would crack under that pressure — and Mother Nature, herself, isn’t immune to that weight, either.
According to a recent study conducted by NASA, swaths of land along the California coastline are sinking at alarming rates. The research highlights how “vertical land motion” is oftentimes unpredictable in a multitude of factors, especially in regard to both speed and severity. (However certain variables like proximity to large bodies of water, position atop mountain ranges, and presence of bedrock — or lack thereof — do offer some insight into an area’s vertical volatility.)
Among the most vulnerable areas in the study were represented by large metros in the SF Bay Area.
“Homing in on the San Francisco Bay Area — specifically, San Rafael, Corte Madera, Foster City, and Bay Farm Island — the team found the land subsiding at a steady rate of more than 0.4 inches (10 millimeters) per year due largely to sediment compaction,” reads the study, showing that San Francisco is also sinking at a similar rate, especially in neighborhoods like the Marina and Bayview. “Accounting for this subsidence in the lowest-lying parts of these areas, local sea levels could rise more than 17 inches (45 centimeters) by 2050. That’s more than double the regional estimate of 7.4 inches (19 centimeters) based solely on tide gauge projections.”
While worthy of concern, the phenomenon of land subsiding, sometimes referred to simply as “subsidence” in urban playing, isn’t novel. It’s a geographical quirk that’s relatively common among large cities.
Cities are inherently unnatural. They consist of the highest concentration of man-made materials anywhere in the world; our ability to stack those materials hundreds of feet toward the clouds creates unique urban skylines; 80% of the land mass occupied by the average city is covered by concrete, leaving just 20% for grasslands, urban forests, and their nature spaces.
Because of their abnormal makeup, the ground beneath — soil layers millions of years old — don’t possess the qualities to support the weight of most cities. Cities, too, often sequester higher-than-average amounts of groundwater trapped in soil layers, causing the land to compact over time.
New York City is sinking. Houston is sinking (exacerbated by the presence of gas and oil extraction.). Seattle is sinking — with some of its downtown structure dropping more than an inch yearly near certain water pumping access points.
But nowhere on the planet is subsidence more glaring or in-your-face than in Mexico City. The most populated metro in the Northern Hemisphere sits inside an area uncomfortably primed to sink. Mexico City sits atop an area formerly swallowed by Lake Texcoco, and, as a result, means large amounts of clay make up the lake-bed-like ground the city was founded on. Mexico City’s population boom, amassing a downtown population of nearly 9 million by the 2020s, has meant a greater reliance on groundwater, thus worsening subsidence.
Mexico City sits 30 feet lower than it did a century ago. You can, quite literally, walk through the second floor of some older buildings that now sit at sidewalk level.
The San Francisco Bay Area’s reality rapid sinking is notable. Unlike Mexico City, the rise in sea levels caused by the climate crisis means these regional metros will face even more complicated issues as coastlines encroach.
How San Francisco and other major cities in the SF Bay Area will look in the next half-century are inextricably tied to our actions now … as we see the current Trump administration gut the very federal agencies responsible for safeguarding us from the worst of these climate catastrophes. What a time to be alive.
How San Francisco and other major cities in the SF Bay Area will look in the next half-century are inextricably tied to our actions now … as we see the current Trump administration gut the very federal agencies responsible for safeguarding us from the worst of these climate catastrophes. What a time to be alive.
