Declining water levels in the Great Salt Lake have revealed something odd in satellite images: dozens of small, circular features along the eastern edge of the drying lakebed in parts of Farmington Bay, Ogden Bay, and Bear River Bay.
University of Utah researchers gained an early clue about these features while traveling by airboat through the lake’s shallow bays years ago. They noticed circular patterns roiling the water surface in certain areas but were not sure why. When water levels dropped and exposed portions of the lakebed, researchers began to find circular features in imagery from Landsat and other satellites and now think they must be related.
The image above (right) shows a cluster of at least seven of the features in Ogden Bay. The OLI (Operational Land Imager) on Landsat 9 acquired the image on September 13, 2025. The image on the left, from the TM (Thematic Mapper) on Landsat 5, shows the same area on September 15, 2011, when water levels were significantly higher. Higher-resolution sensors have imaged dozens of smaller, similar examples to the southwest and south of this cluster.
Their curiosity piqued, the researchers organized field expeditions to explore several of the features from the ground over the past year. “It took some work to reach certain sites since we wanted to avoid using vehicles or other modern equipment that might damage the playa,” said William Johnson, a geologist at the University of Utah.
Instead, they used snow bikes and garden tools to fight through thick patches of reeds to reach the center of the “islands” of vegetation. Once there, they set up piezometers and other monitoring equipment at various depths and distances from the centers of the features to measure the pressure and salinity of the underlying water.
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