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What Is the Deepest Part of the Ocean?


Mariana Trench Map / Kmusser, Wikimedia Commons

Mariana Trench, showing the Challenger Deep

Kmusser, Wikimedia Commons
Question: What Is the Deepest Part of the Ocean?

The ocean's deepest area is the Mariana Trench (also called the Marianas Trench), which is about 11 km (almost 7 miles, or almost 36,000 feet) deep. The trench is 1,554 miles long and 44 miles wide, and is like the Grand Canyon of the ocean, although it is 120 times larger. Contrary to what you might picture, the trench is wide - according to NOAA, almost 5 times wider than it is deep. The Mariana Trench is located in the western North Pacific Ocean.

How Did the Mariana Trench Form?

The Mariana Trench is so deep because it is an area where two of the Earth's plates converge and one (the Pacific plate) is subducted, or dives underneath, the other (the Philippine plate). During this slow process, the Philippine plate also gets pulled down. This combination results in the formation of a deep trench (see map of the Earth's lithospheric plates here).

How Deep Is the Ocean's Deepest Point?

The deepest point in the ocean is, not surprisingly, in the Mariana Trench. It is called the Challenger Deep, after the British ship Challenger II, which discovered this point in 1951 while surveying. The Challenger Deep lies along the southern end of the Mariana Trench near the Mariana Islands.

Various measurements have been taken of the ocean's depth at the Challenger Deep, but it is usually described as about 11,000 meters deep, or close to 7 miles beneath the ocean's surface. At 29,035 feet, Mt. Everest is the tallest spot on Earth, yet if you were to submerge the mountain with its base at the Challenger Deep, it would still have over a mile of water above it.

Have Humans Been To the Ocean's Deepest Point?

Oceanographers Jacques Piccard and Don Walsh explored the Challenger Deep in January 1960 aboard a bathyscaphe named Trieste. The submersible carried the scientists approximately 11,000 meters (about 36,000 feet) into the Challenger Deep. The trip down took about 5 hours, and then they spent only about 20 minutes on the sea floor, where they viewed an "ooze" and some shrimp and fish, although their view was hampered by the sediment stirred up by their ship. They then traveled about 3 hours back to the surface.

Since then, unmanned submersibles from Japan (the Kaikō in 1995) and Woods Hole Oceanographic Institution explored the Challenger Deep.

Until March 2012, no human besides Piccard and Walsh had traveled to the Challenger Deep. But on March 25, 2012, filmmaker (and National Geographic Explorer) James Cameron became the first person to make a solo voyage to the deepest point on Earth. His 24-foot tall submersible Deepsea Challenger, reached 35,756 feet (10,898 meters) after an approximately 2.5-hour descent. Unlike Piccard and Walsh's historic first exploration, Cameron spent more than 3 hours exploring the trench, although his attempts to take biological samples at the ocean bottom were hampered by technical glitches.

What Lives in the Deepest Part of the Ocean?

Despite cold temperatures, extreme pressure (to us, anyway) and lack of light, marine life does exist in the Mariana Trench. Single-celled protists called foraminifera, crustaceans and other invertebrates and even fish have been found there.

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