GRAVITY ANOMALY MAP OF NORTH AMERICA

Abstract

The Gravity Anomaly Map of North America is the product of a 12-year international effort to compile, critically edit and merge gravity anomaly data on a continental and global scale. This color-pixel map, printed on four quadrant sheets at a scale of 1:5 000 000 and including a fifth sheet showing a color index map with data references, is the first such map at this large scale to include several hundreds of thousands of precise surface data of the United States, Canada, Mexico and Central America as well as other high-quality surface data from neighboring continental and oceanic areas. The map, which shows Bouguer gravity anomalies on land and free-air gravity anomalies over oceans, is remarkable for its detail. Sixty-six colors or shadings have been used in a carefully conceived nonlinear scheme to show anomalies at a 5 or 10 mGal interval over a dynamic range from about −300 mGal to +130 mGal.