In the second half of the 20th century, the foundation of the U.S. Geological Survey’s national map series was the handcrafted 7.5-minute topographic map. Times change, budgets get squeezed and ...
On USGS quadrangle maps from 1947-1992, oil wells are marked by hollow black circles. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by ...
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