Eighty percent of the ocean floor, hidden deep below the waves, has not been mapped. It is out of the accurate range of surface sonar. But now a series of new maps have been produced, twice as precise as anything done before, and they reveal thousands of previously uncharted sea mountains as well as fractures at the ocean bottom that produce deep-sea earthquakes.

You can see some of the maps here. The images, published Thursday in Science, are the product of sensors on two satellites. The sensors, called altimeters, detect very small changes in ocean surface height. That surface bends down a bit over seamounts, for example, pulled by the gravity of the giant structures, and it mirrors their shapes. David Sandwell, a geophysicist at the Scripps Institution of Oceanography, and his colleagues used that phenomenon to produce these startlingly detailed charts of the deep, even features buried under mile-thick sediment layers. This newly charted topography will help scientists better understand how ocean waters circulate and mix, activity that strongly influences Earth’s climate. And it can add to their understanding of how continents formed early in the planet’s history, and why clusters of quakes occur in specific places now.