A new academic study found nearly half of Houston's land is subsiding at least 1/5 of an inch each year, outpacing the country's other large urban areas.

The study, published in the journal Nature Cities, found that 42% of Houston's land area was sinking about one-fifth inch per year, with 12% sinking at more than double that rate.

Satellite data revealed that Houston is the fastest-sinking city in the U.S., and that all of the other biggest cities are dropping in at least some areas. Researchers say groundwater extraction is largely to blame for the sink.