Science News reports:

The number of known mountains in Earth’s oceans has roughly doubled. Global satellite observations have revealed nearly 20,000 previously unknown seamounts, researchers report in the April Earth and Space Science.

Just as mountains tower over Earth’s surface, seamounts also rise above the ocean floor. The tallest mountain on Earth, as measured from base to peak, is Mauna Kea, which is part of the Hawaiian-Emperor Seamount Chain.

These underwater edifices are often hot spots of marine biodiversity. That’s in part because their craggy walls — formed from volcanic activity — provide a plethora of habitats. Seamounts also promote upwelling of nutrient-rich water, which distributes beneficial compounds like nitrates and phosphates throughout the water column. They’re like “stirring rods in the ocean,” says David Sandwell, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego.

More than 24,600 seamounts have been previously mapped. One common way of finding these hidden mountains is to ping the seafloor with sonar. But that’s an expensive, time-intensive process that requires a ship. Only about 20 percent of the ocean has been mapped that way, says Scripps earth scientist Julie Gevorgian. “There are a lot of gaps.”

So Gevorgian, Sandwell and their colleagues turned to satellite observations, which provide global coverage of the world’s oceans, to take a census of seamounts. [Continue reading…]