How Deep Is the Deepest Part of the Ocean?

The deepest part of the ocean is the Marianas Trench off the Philippine Islands in the South Pacific. There the sea floor lies 11,034 meters (36,201 feet) below the waves. So the distance to the surface is more than a mile greater than the height of Mount Everest. The Mariana Trench is located at a convergent plate boundary. Here two converging plates of oceanic lithosphere collide with one another.

At this collision point, one of the plates descends into the mantle. At the line of contact between the two plates, the downward flexure forms a trough known as an ocean trench. Ocean trenches form some of the deepest locations in Earth’s oceans.The Challenger Deep in the Mariana Trench is the deepest known point in Earth’s oceans.

Jacques Piccard and Lt. Donald Walsh descended to the bottom of the Marianas Trench on January 23, 1960 in the United States Navy bathyscaphe Trieste. It took four and a half hours to make the trip to the bottom, where the water pressure was eight tons to the square inch. This is the nearest men have come to making a journey to the center of the earth.

The average depth of water in the world’s oceans is 12,000 feet. But, apart from the Marianas Trench, there are other trenches in the seabed more than six miles deep. The floor of the ocean is, of course, as well defined with canyons and “mountain peaks” as the dry land of the earth, something we do not normally consider when we look at the ocean surface.

The first depth measurements in the Mariana Trench were made by the British survey ship HMS Challenger, which was used by the Royal Navy in 1875 to conduct research in the trench. The greatest depth that they recorded at that time was 8,184 meters (26,850 feet).

In 1951, another Royal Navy vessel, also named the “HMS Challenger,” returned to the area for additional measurements. They discovered an even deeper location with a depth of 10,900 meters (35,760 feet) determined by echo sounding. The Challenger Deep was named after the Royal Navy vessel that made these measurements.

In 2009, sonar mapping done by researchers aboard the RV Kilo Moana, operated by the University of Hawaii, determined the depth to be 10,971 meters (35,994 feet) with a potential error of ± 22 meters. The most recent measurement, done in 2010, is the 10,994 meter (± 40 meter accuracy) measured by the United States Center for Coastal & Ocean Mapping.

In 2010 the United States Center for Coastal & Ocean Mapping measured the depth of the Challenger Deep at 10,994 meters (36,070 feet) below sea level with an estimated vertical accuracy of ± 40 meters.

Content for this question contributed by Vincent Majerowicz, resident of Healdsburg, Sonoma County, California, USA