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The Mariana Trench, at a glance
The ocean’s deepest point, reached by only three crewed dives
~10,935 m
Challenger Deep’s depth, the lowest point on Earth’s surface.
23 Jan 1960
Don Walsh and Jacques Piccard made the first crewed descent.
26 Mar 2012
James Cameron became the first person to dive there solo.
~1,086 bar
Pressure at the bottom, like 1,800 elephants on one point.
How Deep Is the Mariana Trench, and How Did It Form?
Where is the trench, and what made it so deep?
- The Mariana Trench lies in the western Pacific Ocean, near the Mariana Islands, northeast of the Philippines.
- It’s crescent-shaped, stretching about 2,550 km long and 69 km wide.
- Its deepest point is Challenger Deep, at roughly 10,935 metres (35,876 feet) below sea level, the lowest point on Earth’s surface.
- The trench formed through subduction. The old, dense Pacific Plate is forced beneath the smaller Mariana Plate, a process that’s been ongoing for over 50 million years.
- Pressure at Challenger Deep reaches about 1,086 bar, roughly equivalent to the weight of 1,800 elephants pressing down on a single point.
Q1. True or False: Challenger Deep, the Mariana Trench’s deepest point, is the lowest point on Earth’s surface.
Q2. True or False: The Mariana Trench formed because the Mariana Plate is subducted beneath the Pacific Plate.
Who Has Actually Reached Challenger Deep?
Why have only three crewed dives ever reached the bottom?
- The trench takes its name from the HMS Challenger, a British survey ship that first charted its extreme depth in 1875.
- On 23 January 1960, U.S. Navy Lieutenant Don Walsh and Swiss oceanographer Jacques Piccard reached Challenger Deep in the bathyscaphe Trieste. They spent just 20 minutes at the bottom.
- On 26 March 2012, filmmaker James Cameron became the first person to reach Challenger Deep solo, in the submersible DEEPSEA CHALLENGER. He explored for several hours, far longer than the 1960 dive.
- As of 2026, only these three crewed descents to the very bottom have ever been made, though several later expeditions have reached it too.
Q3. True or False: Don Walsh and Jacques Piccard made the first crewed descent to Challenger Deep, in 1960.
Q4. True or False: James Cameron was part of the first crewed dive to Challenger Deep in 1960.
Think it through, before reading on. James Cameron’s 2012 solo dive lasted several hours; the 1960 crewed dive lasted just 20 minutes. Why such a big gap, despite going to the exact same depth?
Show the explanation
Submersible technology advanced enormously in the 52 years between the two dives. The Trieste was a basic bathyscaphe built mainly to survive the trip down and back; DEEPSEA CHALLENGER was purpose-built with better life support, lighting, and cameras, letting Cameron stay and actually explore rather than just confirm he’d reached bottom.
Remember the trap. Don’t mix up the two dives’ pilots. Walsh and Piccard reached the bottom together in 1960, in the Trieste. Cameron reached it alone in 2012, in DEEPSEA CHALLENGER.
What Lives at the Bottom of the Ocean’s Deepest Point?
What has science found living, and polluting, at Challenger Deep?
- Life still survives at these depths. The Mariana snailfish, small, pink, and scaleless, is the top predator around 8,000 metres down, the deepest-living fish known.
- Other residents include giant single-celled organisms called xenophyophores, and pale amphipods that scavenge the seafloor.
- If Mount Everest were placed inside Challenger Deep, its summit would still sit more than a mile underwater. That’s a scale most people find hard to picture from the surface.
- Even this remote a place isn’t free of human impact. A plastic bag was documented on the floor of Challenger Deep in 2019, along with other plastic waste found in the guts of creatures collected there.
- The trench’s extreme, alien conditions make it valuable to scientists well beyond oceanography. It’s studied for clues to how life might survive in equally hostile environments elsewhere, including other planets’ oceans.
Q5. True or False: The Mariana snailfish is the deepest-living fish known.
Q6. True or False: Challenger Deep is so remote that no human-made pollution has ever been found there.
Quick Q&A
How deep is Challenger Deep?
Roughly 10,935 metres, the lowest point on Earth’s surface.
How did the Mariana Trench form?
Through subduction: the Pacific Plate is forced beneath the smaller Mariana Plate, over 50 million-plus years.
Who made the first crewed descent to Challenger Deep, and when?
Don Walsh and Jacques Piccard, in the bathyscaphe Trieste, on 23 January 1960.
What is the deepest-living fish known?
The Mariana snailfish, found as the top predator around 8,000 metres down.
- NDA-NA-2 2017 — Asked which ocean floor holds the Mariana Trench. The answer is the western Pacific Ocean, near the Mariana Islands east of the Philippines.
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