Did you know the ocean off New York City hides a gorge that rivals the Grand Canyon? Or that two dozen Empire State Buildings, stacked one on top of the other, can fit inside the Pacific Ocean’s Mariana Trench? And with only a fraction of its towering peak seen above the water, Hawai’i’s now inactive submerged volcano Mauna Kea is 33,474 feet tall—nearly a mile higher than Mount Everest.
Geological formations below the surface of the water—mountain ranges, valleys, volcanoes—are often much bigger and more impressive in scale than those above. They also provide clues to geoformations on Earth and possibly even other planets.
For instance, the Mid-Atlantic Ridge, where the Eurasian and North Atlantic plates meet at the bottom of the Atlantic Ocean, is the largest mountain range on Earth. And the underwater volcano Tamu Massif, located in the Pacific Ocean, has recently been identified as the planet’s largest volcano.
The formation of new land is happening all the time, both above and below water. New islands created by volcanic eruption—for example Surtsey, which emerged off Iceland in 1963—offer researchers unique opportunities to learn not only more about the evolution of volcanoes but how pristine areas become populated. Consider the Hawaiian Islands, empty of terrestrial life as a newly formed volcanic chain millions of years ago with the nearest continent 2,500 miles away. Today, Hawai’i is one of the most biodiverse places on Earth, with many species that are endemic—that is, found nowhere else.
The 2014 emergence of a volcanic island in the South Pacific has even opened a window into the geological history of other planets. A comparison of features on this new island in the Kingdom of Tonga showed similar structures to those found on Mars, which appear to indicate that billions of years ago the Red Planet had water, as well as an abundance of volcanic activity.
A version of this story originally appeared in the Spring 2018 issue of Rotunda, the Member magazine.