Land Subsidence in California (IMAGE) Stanford University Caption Land surface in California’s San Joaquin Valley subsided about 29 feet (9 meters) between 1925 and 1977 because of groundwater depletion. Signs on the telephone pole indicate the former elevations of the land surface in 1925 and 1955. Credit Richard Ireland, U.S. Geological Survey (1977) Usage Restrictions CREDIT: Richard Ireland, U.S. Geological Survey (1977) License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.