Scientists used high-resolution radar satellites and discovered a “mind-boggling” 19,000 volcanoes.
Up until very recently, only about one-quarter of the planet’s seafloor had been mapped using sonar, which uses sound waves to detect objects hidden underwater.
A 2011 sonar census found more than 24,000 seamounts, or undersea mountains formed by volcanic activity. However, there are more than 27,000 seamounts that remain uncharted by sonar, according to Live Science.
However, our knowledge of what lies beneath the ocean’s surface has changed for the better. A team of oceanographers at the Scripps Institution of Oceanography, working with a colleague from Chungnam National University and another from the University of Hawaii, has mapped 19,000 previously unknown undersea volcanoes in the world’s oceans using radar satellite data.
Their paper was published in the journal Earth and Space Science, and the group describes how they used radar satellite data to measure seawater mounding to find and map undersea volcanoes and explains why it is important that it be done.
“It’s just mind-boggling,” David Sandwell, a marine geophysicist at the Scripps Institution of Oceanography who worked on the survey, told Science magazine.
Just like dry land masses, the ocean floor features a wide variety of terrain, and naturally, just as it is with dry land, mountains really stand out. And another interesting point to consider – Just like dry land mountains, sea floor mountains can be created by tectonic plates pushing against one another, or by volcanos erupting.
No one knows just how many sea mounts exist today. So far, researchers have mapped a collection of seamounts in the northeast Atlantic Ocean, and if you add the 25 percent of the sea floor already mapped, that still leaves a vast area unmapped.
This can be a problem for submarines—twice U.S. submarines have collided with seamounts, putting such vehicles and their crew at risk. But not knowing where the seamounts are located presents another problem. It prevents oceanographers from creating models depicting the flow of ocean water around the world.
This new study shows that scientists don’t need to rely on sonar surveys to see what is on the sea floor. Instead, they used data from radar satellites. Satellites cannot actually see the seamounts.
Instead, they measure the altitude of the sea surface, which changes due to changes in gravitational pull related to seafloor topography; an effect known as sea mounding. This is how they found the 19,000 seamounts.
Scientists pulled data from several satellites, including the European Space Agency’s CryoSat-2, and found that they could detect underwater mounds as small as 3,609 feet (1,100 meters) tall, which is the lower limit of what constitutes a seamount, according to the Science article.
The biggest takeaway from this study is that seamounts have a very strong impact on deep-sea ocean flow. As currents run into seamounts, they are pushed upward, carrying colder water with them, and mix in unknown ways.
Mapping such currents has become more important as the oceans absorb more heat and carbon dioxide from the atmosphere and freshwater melt, due to ongoing climate change.