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USGS Mineral Resources: Isostatic residual gravity anomaly grid for the conte...
From the site: "Measurements of the gravitational field vary slightly from place to place due to the composition and structure of Earth's crust. This digital grid describes the... -
USGS Mineral Resources: Aeroradiometric Surveys of North America
From the site: "Data generated by aerial sensing of radiation emanating from the earth's surface provides general estimates of the geographic distribution of Uranium, Thorium,...