The Mariana Trench is a crescent-shaped trench in the floor of the western Pacific Ocean, and its deepest point is about 10.9 kilometers (6.8 miles) below the sea surface. That point, called the Challenger Deep, is the deepest known place in the ocean as of 2026. NOAA, the US ocean and weather agency, gives its depth as about 10,935 meters (35,876 feet).

Size

The depth is measured from sea level down to the deepest point of the sea floor. The Challenger Deep lies at the southern end of the trench, several hundred kilometers southwest of the US island of Guam.

In June 2020, a submersible made a series of dives to the bottom of the Challenger Deep. Researchers worked out the depth from the water pressure it recorded there. They corrected for the properties of the seawater above it, for air pressure and for local differences in gravity. The result was 10,935 meters below mean sea level, give or take 6 meters.

Other measurements have used sound, timing echoes from the sea floor. Some sources give a rounded figure of about 11,000 meters (36,000 feet).

Size comparisons

The Challenger Deep is about three times as deep as the ocean's average depth of 3,682 meters (12,080 feet).
If Mount Everest, 8,849 meters (29,032 feet) tall, stood on the bottom, its summit would still be about 2.1 kilometers (6,800 feet) under water.
About 100 American football fields, each 120 yards (110 meters) long including the end zones, stood on end one above another would reach from the bottom to the surface.
The nucleus of Halley's Comet, about 15 kilometers (9.3 miles) long, would stick out about 4 kilometers (13,000 feet) above the waves if stood on end in the Challenger Deep.

How the trench formed

Ocean trenches are the deepest parts of the ocean floor. They form where two of the huge slabs of rock that make up Earth's outer layer, called tectonic plates, push together and one sinks beneath the other. This sinking is called subduction.

The Mariana Trench marks where the fast-moving Pacific Plate meets the slower Philippine Plate. The Mariana Islands, a curved chain of volcanic islands, run alongside it.

Pressure and exploration

Water pressure grows with depth. Every 10.06 meters (33 feet) of seawater adds one atmosphere of pressure, the pressure of the air at sea level. At the bottom of the Challenger Deep, that adds up to more than 1,000 times the pressure at sea level.

The trench was first sounded, or measured for depth, by the crew of the ship HMS Challenger in 1875, and the Challenger Deep is named after that ship. Since January 2009, part of the trench's floor has been protected as the Mariana Trench Marine National Monument of the United States.

Sources

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