1.   Although the gravity map reveals subtle details of the midocean ridges, the ridges also highlight its limitations as a guide to seafloor topography.

2.   Across the gravity map the fracture zones streak, and like frozen whoosh lines they visualize the growth of oceans and the drift of continents.

3.   In general the gravity map matches topography only over relatively short horizontal distances, a hundred miles or so.

4.   Sandwell and Smith are now in the process of making a real map of seafloor topography that corrects for these limitations of the gravity map.

5.   The agency says it is integrating the gravity map into other databases, including those from acoustic mapping expeditions, and will publish updated versions in the months ahead.

6.   The Germans never looked into commercial uses for the map, which is the only detailed gravity map completed to date for northern Chile.

7.   The gravity map of the Yucatan shows a horseshoe-shaped crater, its southeastern side deep and its northwestern side increasingly shallow.