If I had a different career, I’d be a deep-sea explorer. With vast swaths of the ocean still unknown, I’d discover new marine species, or research ancient shipwrecks. I’d also hike underwater volcanoes—all 43,000-plus of them.
Well, maybe no one actually hikes these volcanoes, also known as seamounts. To explorers like me, though, the first step is to know how many volcanoes exist, and where they’re located. A decade ago, we knew of almost 25,000. One study has discovered an additional 19,000. And we know there are even more out there.
How could thousands of seamounts remain hidden for so long? The ocean covers 71 percent of the Earth’s surface. To find volcanoes, researchers often use sonar. This method, however, relies on ships or submarines, meaning that only a fraction of the seafloor can be mapped at a time.
If I want to explore underwater geography, my best bet might be to not go underwater at all. Instead, I could use satellite altimetry, which measures the height of the ocean surface. Seamounts tend to rise straight out of a flat seabed, and can reach as high as six miles. As a result, the huge mountains exert a small gravitational pull, which shapes surface water into a subtle mound. Satellites can detect the slight mounds, and thus the volcanoes beneath.
Seamounts would be perfect for my deep-sea exploration. I could study the many aquatic creatures that live on the slopes. I could learn about the plate tectonics that create these volcanoes. And I could continue to map the great mystery of our planet’s watery depths.