Its southern end holds the deepest known point in any ocean, about 10,935 metres down
Roughly 11 km; the average ocean depth is about 3,682 m
Geography · Physical geography
The Mariana Trench
Western Pacific Ocean — east of the Mariana Islands, a US territory
The deepest place in the ocean: a crescent-shaped subduction trench in the western Pacific whose southern end, the Challenger Deep, reaches about 10,935 metres below the surface. Put Everest in it and its summit would still be more than two kilometres underwater. Only a handful of crewed descents have ever reached the bottom, beginning with the Trieste in 1960.
How to spot them
- ▸The deepest point in any ocean, about 11 km down
- ▸Quiz clue: 'Challenger Deep', 'Trieste', 'Guam', 'Pacific Plate', 'hadal zone'
- ▸Named after a British survey ship of the 1870s that first sounded it
- ▸James Cameron dived to the bottom alone in 2012
Key facts
Formed where the Pacific Plate is forced beneath the smaller Mariana Plate
A classic oceanic–oceanic subduction zone, with a volcanic island arc behind it
First sounded in 1875 by a British survey ship whose name the deepest spot still carries (1875)
HMS Challenger, on the voyage that founded oceanography
Jacques Piccard and Don Walsh reached its floor in the bathyscaphe Trieste in January 1960 (1960)
They saw what they took to be a flatfish; the observation is still disputed
James Cameron made the first solo descent to its floor in 2012, in the Deepsea Challenger (2012)
The first crewed return in 52 years
Its deepest waters still hold living things — giant amphipods and single-celled xenophyophores
The hadal zone; pressure there is over 1,000 times atmospheric
It is a US National Monument, though its floor is far beyond the reach of any coastline
Designated by President George W. Bush in 2009
Quick-fire facts
- •The Challenger Deep lies about 10,935 m below the surface — NOAA's figure, with other surveys giving 10,920–10,994 m
- •The trench is roughly 2,550 km long and about 69 km wide
- •It is named for the nearby Mariana Islands, which are named for Mariana of Austria
- •Pressure at the bottom exceeds 1,000 atmospheres, about 1,086 bar
- •HMS Challenger first sounded it in 1875; the deepest point takes its name from the ship
- •Trieste's 1960 descent by Piccard and Walsh was the first; Cameron's 2012 solo dive was the second crewed one
- •Victor Vescovo has since made repeated descents in the submersible Limiting Factor
- •Common misconception: it is deep because of subduction, not erosion, and Mount Everest dropped into it would still be about 2 km short of the surface
Drill it — 8 cards
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Sources
- NOAA National Ocean Service — How deep is the ocean?
- NOAA National Centers for Environmental Information — ETOPO Global Relief Model