When familiar parts of a city start to sink or rise, it can indicate changes in the geology or human activity, which worries researchers. To explore these unusual movements, scientists from NASA’s Jet Propulsion Laboratory (JPL) aimed to understand the causes behind them. They used satellite and ground-based measurements to track shifts in the urban landscape. Their findings, published in the journal Science Advances, showed the complex relationship between natural and human influences, causing cities to gradually rise and fall over time.
Radar Reveals Shifting Lands
The team at JPL in Southern California and Rutgers University in New Jersey focused on analyzing the movements across the city of New York from 2016 to 2023 using an advanced technique based on remote sensing called the interferometric synthetic aperture radar (InSAR), according to NASA. Satellites can map ground movement by sending radar signals to the surface and measuring the time it takes for the signals to come back. When a second measurement is taken from the same spot, small changes in the signal’s travel distance can be detected. These slight differences create an interference pattern called an interferogram, which acts like a detailed map of ground motion, as reported by ZME Science.
With this technique, scientists can see areas that are sinking or rising with remarkable accuracy, sometimes down to just a few millimeters. It provides crucial information about changes in the landscape over time. Also, it included 2D and 3D monitoring of the region to reveal the topography of the land. New research published in the journal Nature Cities, developed on early works on this topic, used satellite measurements to create a detailed picture of the rise and fall of the land. However, a popular reasoning for this rise and fall is directly related to the extraction of groundwater and how the excessive process can cause the ground to sink.
Other Factors at Play
New York’s sudden fall can be linked to the massive layer of bedrock underneath the U.S. that moved down due to the pressure from glaciers from the last Ice Age, through many global changes, and is moving back to its older places. However, this happens in multiple cycles, causing the subsidence rates to change in the region. Areas like Texas are in the red due to the large, growing industry of agriculture, taking in huge amounts of water, as reported by The New York Times…