How deep is the ocean?

The prospect of comprehending just how vast and deep Earth’s oceans are is a challenging one. Earth’s surface is dominated by the Atlantic, Pacific, Indian, Arctic, and Southern oceans, which together cover some 71 percent of the planet and whose average collective depth is 12,100 feet (3,688 metres). What is even more difficult to grasp is that many parts of the oceans are much deeper, beyond anything at normal human scales, and they are so deep that comparing them with the sizes of the world’s greatest structures and largest well-known points of interest makes them only slightly more fathomable.

At 36,070 feet (10,994 meters) below sea level, Challenger Deep in the Pacific Ocean’s Mariana Trench is the ocean’s deepest known point. To truly understand how deep that is, one can compare it to Earth’s highest point on land, Mount Everest in the Himalayas of Asia. Everest stands 29,032 feet (8,849 metres) above sea level. Although the depth of the world’s deepest darkest oceanic abyss is greater than the height of the world’s tallest peak, the magnitudes of each location’s distance from sea level are still relatively comparable to each other. Within this context, it may be helpful to know that the bulk of the world’s seafloor is only about one-third to about one half as deep, lying between about 13,100 and 16,400 feet (4,000 and 5,000 metres) below sea level.

These benchmarks can be used to place familiar terrestrial landmarks and human structures in context, and in doing so the challenge of understanding the sheer greatness of ocean depth becomes a bit easier. (The graphic contrasts relative ocean depth with the sizes of various locations, structures, and feats.) For example, the depth at which most of Earth’s seafloor lies is about four to five times greater than the height of the world’s tallest building, the Burj Khalifa skyscraper in the United Arab Emirates, which measures 2,717 feet (828 metres) tall; however, the depth of the Challenger Deep is more than ten times greater than the Burj Khalifa’s height. The heights of famous natural landmarks fare somewhat better in measuring up; for example, the depth of the Grand Canyon from the canyon’s rim to its deepest point and the height of El Capitan (a well-known mountain in Yosemite National Park) above sea level measure 6,000 feet (1,800 metres) and 7,569 feet (2,307 metres), respectively. The depths of some of the world’s best-known deep-ocean shipwrecks are even more comparable: the Titanic and the OceanGate submersible, Titan, both of which sank in the Atlantic Ocean, came to rest at a depth of about one-third that of the Challenger Deep. In addition, in the deepest known shipwreck, the USS Samuel Roberts sank beneath the Philippine Sea during World War II to a depth of 22,621 feet (6,895 metres), which is more than half of the depth of the deepest point in the ocean.

Still, the world’s tallest mountains, such as Mount Everest and Mount Aconcagua (the Western Hemisphere’s highest point, which is located in Argentina and rises to 22,840 feet [6,962 metres]), are the only terrestrial features whose heights compare favorably to the ocean’s deepest places. Both of these peaks have been climbed on foot by human beings, so the effort required to travel the vertical distances to their summits and back are known by numerous people, a fact which may help to reduce the conundrum of plumbing the ocean’s depth in human terms for some. The heights of the summits of Everest, Aconcagua, and several other peaks are actually greater than the depth at which most of Earth’s seafloor lies—and Everest’s height, despite being only a little more than three-quarters as great as the depth of the Challenger Deep, is greater than the deepest parts of the Atlantic, Indian, Southern, and Arctic oceans. The only place in those oceans that comes close is the Milwaukee Depth in the Atlantic’s Puerto Rico Trench, whose depth measures nearly 1,640 feet (500 metres) shorter than the height of Everest’s summit.