About twice as many underwater mountains have been discovered. In the April issue of Earth and Space Science, researchers report that global satellite measurements have uncovered approximately 20,000 previously unknown seamounts.
Seamounts are underwater mountains that are as tall as the tallest mountains on land. Mauna Kea, located in the Hawaiian-Emperor Seamount Chain, has the distinction of being the world's highest mountain when measured from its base to its top.
Such submerged structures are frequently rich in marine life (SN: 10/7/16). One reason for this is the diversity of environments offered by the jagged walls of these volcano-formed mountains. The upwelling of nutrient-rich water facilitated by seamounts also helps to disperse these chemicals, such as nitrates and phosphates, throughout the water column. They are analogous to "stirring rods in the ocean," as described by David Sandwell, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego.
There are around 24,600 seamounts that have been mapped. Sonar pings of the seabed are often used to locate these submerged mountains (SN: 4/16/21). However, doing so requires a ship, which is both costly and time-consuming. According to Julie Gevorgian, an earth scientist at Scripps, only approximately 20% of the ocean has been mapped in this manner. The gaps are rather large.
To perform a census of seamounts, Gevorgian, Sandwell, and coworkers relied on satellite data due to their worldwide scope.
The group studied satellite readings of sea level to have a better understanding of the problem. Researchers sought for lumps as small as a few centimeters, evidence of a seamount's gravitational effect. The existence of a seamount modifies the local gravitational field by a little amount due to the density difference between rock and water. To quote Sandwell, "there's an extra gravitational attraction," which causes water to gather above the seamount.
Using this method, the crew located 19,325 previously undiscovered seamounts. To verify the veracity of the newly found seamounts, the researchers verified some of their findings with sonar scans of the seabed. Researchers believe that the majority of the recently found undersea mountains range in height from 700 to 2,500 meters.
Nonetheless, some might be dangerous to sailors. "There's a point when they're shallow enough that they're within the depth range of submarines," says David Clague, a marine geologist at the Monterey Bay Aquarium Research Institute in Moss Landing, California, who was not involved in the study. The nuclear submarine USS Connecticut collided with an unmapped seamount in the South China Sea in 2021. The ship is still in a shipyard in Washington state getting fixed up.
CITATIONS
J. Gevorgian et al. Global distribution and morphology of small seamounts. Earth and Space Science. Vol. 10, April 2023. doi: 10.1029/2022EA002331.
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