The number of known mountains in the Earth’s oceans has approximately doubled. Global satellite observations revealed almost 20,000 previously unknown seamounts researchers report in the April journal Earth and Space Science .
Just as mountains rise above the Earth’s surface, seamounts also rise above the ocean floor. The tallest mountain on Earth, measured from base to summit, is Mauna Kea, which is part of the Hawaiian Imperial Seamount chain.
These underwater structures are often hotspots for marine biodiversity . This is partly due to the fact that their rocky walls, formed by volcanic activity, provide a variety of habitats. Seamounts also help lift nutrient-rich water, which distributes beneficial compounds such as nitrates and phosphates throughout the water column. They are 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 previously been mapped. One common way to find these hidden mountains is to search the seabed with a sonar. But it’s an expensive, time-consuming process that requires a ship. Only about 20 percent of the ocean has been mapped this way, says Scripps scientist Julie Gevorgian. “There are a lot of gaps.”
So Gevorgian, Sandwell and their colleagues turned to satellite observations that provide global coverage of the oceans to conduct a census of seamounts.
The team studied satellite measurements of sea surface height. The researchers were looking for centimeter-scale irregularities caused by the gravitational influence of the seamount. Because rock is denser than water, the presence of a seamount slightly changes the Earth’s gravitational field at that location. “There is an additional gravitational pull,” says Sandwell, “that causes the water to accumulate over the seamount.
Using this technique, the team discovered 19,325 previously unknown seamounts. The researchers compared some of their observations with sonar maps of the sea floor to confirm that the newly discovered seamounts are likely real. According to the researchers’ estimates, most of the newly discovered seamounts are on the small side — about 700 to 2,500 meters high.
However, it is possible that some of them may pose a danger to seafarers. “There’s a point where they’re so shallow that they’re in the submarine depth range,” says David Klague, a marine geologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, who was not involved in the study. . In 2021, the nuclear submarine USS Connecticut encountered an unknown underwater mountain in the South China Sea. The vessel is still undergoing repairs at a shipyard in Washington state.