How Deep Is the Mariana Trench? The Deepest Point on Earth

The Mariana Trench is the deepest oceanic trench on Earth, located in the western Pacific Ocean east of the Mariana Islands. Its deepest point, the Challenger Deep, reaches approximately 10,935 meters (35,876 feet) below sea level. The trench stretches roughly 2,550 kilometers long and averages 69 kilometers wide, forming a crescent-shaped scar on the ocean floor.

Introduction

The trench was formed by the subduction of the Pacific Plate beneath the smaller Mariana Plate, a process that has been ongoing for millions of years. The extreme depth creates conditions almost inconceivable on the surface: water pressure exceeds 1,000 atmospheres, temperatures hover just above freezing, and perpetual darkness prevails. Yet life exists even here.

The Short Answer

• Maximum Depth: 10,935 m (35,876 ft) at Challenger Deep
• Length: ~2,550 km
• Width: ~69 km average
• Pressure at Bottom: ~1,086 atmospheres (15,931 psi)

The Challenger Deep, named after the HMS Challenger expedition that first surveyed it in 1875, is located at the southern end of the Mariana Trench at approximately 11.3°N, 142.2°E. The exact depth has been refined through multiple measurements: the most precise measurement, by the research vessel DSSV Pressure Drop in 2019, placed the deepest point at 10,935 meters.

To put this depth in perspective: if Mount Everest (8,849 m) were placed at the bottom of the Challenger Deep, its summit would still be over 2,000 meters below the ocean surface. The depth is equivalent to nearly 11 kilometers — roughly the cruising altitude of a commercial jet airliner, but straight down into the ocean.

The Science Behind It

• Formation: Subduction of Pacific Plate beneath Mariana Plate
• Age: Subduction began ~50 million years ago
• Pacific Plate Age: ~170 million years old (oldest oceanic crust on Earth)
• Temperature at Bottom: 1-4°C

The Mariana Trench is so deep because the Pacific Plate being subducted there is among the oldest and densest oceanic crust on Earth, roughly 170 million years old. As oceanic crust ages, it cools and becomes denser, causing it to sink more steeply into the mantle when subducted. The steep angle of subduction creates the extreme depth.

The trench is seismically active, with frequent earthquakes generated by the subducting plate. The deepest earthquake ever recorded occurred at 751 kilometers depth beneath the trench in 2004. Volcanic activity associated with the subduction has created the Mariana Islands, a volcanic arc running parallel to the trench.

Types & Variations

• Challenger Deep: 10,935 m — deepest point (southern end)
• Sirena Deep: 10,714 m — second deepest point (200 km east)
• HMRG Deep: 10,809 m — third deepest (eastern margin)

The Challenger Deep is not a single point but a relatively flat area roughly 11 kilometers long and 1.6 kilometers wide at the trench bottom. Within this area, the deepest sounding of 10,935 meters was recorded. The Sirena Deep, located roughly 200 kilometers to the east, is the second deepest known point at 10,714 meters.

The Mariana Trench contains several distinct deep areas along its length. The trench is not uniformly deep; its floor varies between roughly 7,000 and 11,000 meters, with the greatest depths concentrated in the southern section where the subducting plate is oldest and densest.

Famous Examples

• 1960: Trieste: Jacques Piccard and Don Walsh — first to reach the bottom
• 2012: Deepsea Challenger: James Cameron — first solo descent
• 2019: DSV Limiting Factor: Victor Vescovo — deepest solo dive (10,928 m)
• 2020: Fendouzhe: Chinese submersible reached 10,909 m

On January 23, 1960, Jacques Piccard and Don Walsh descended to the Challenger Deep in the bathyscaphe Trieste, reaching a depth of approximately 10,916 meters. The dive lasted nearly 5 hours down and 3 hours at the bottom, where they observed a flatfish, proving that vertebrate life exists at the greatest ocean depths.

James Cameron's 2012 solo dive in the Deepsea Challenger reached 10,908 meters. In 2019, Victor Vescovo made the deepest recorded dive to 10,928 meters as part of the Five Deeps Expedition, which visited the deepest point in each of the world's five oceans. China's Fendouzhe submersible reached 10,909 meters in 2020.

Why It Matters

• Life at Extremes: Reveals what life can endure — implications for astrobiology
• Pollution: Microplastics have been found at the bottom of the Mariana Trench
• Plate Tectonics: Key location for studying subduction processes
• Technology: Drives innovation in materials science and deep-sea engineering

The discovery of life at the bottom of the Mariana Trench has profound implications for astrobiology — the search for life beyond Earth. If organisms can survive the crushing pressure, near-freezing temperatures, and total darkness of the hadal zone, life might also exist in similarly extreme environments elsewhere in the solar system, such as beneath the ice of Jupiter's moon Europa.

Perhaps the most sobering finding from deep trench exploration is the presence of human pollution at the greatest depths. Microplastics have been found in the sediment and in amphipods at the bottom of the Mariana Trench. A plastic bag was observed at 10,898 meters during a 2018 dive. The deepest point on Earth is not immune to human impact.

Key Facts

• The Mariana Trench reaches 10,935 m at the Challenger Deep — the deepest point on Earth.
• Pressure at the bottom exceeds 1,086 atmospheres — over 1,000 times surface pressure.
• Only 27 people have been to the Challenger Deep (as of 2024), fewer than have walked on the Moon.
• The trench formed from subduction of the ~170-million-year-old Pacific Plate.
• Microplastics and a plastic bag have been found at the bottom of the trench.

Fun Facts

• More people have walked on the Moon (12) than had visited the Challenger Deep before 2019.
• The pressure at the bottom would crush a styrofoam cup to the size of a thimble.
• Piccard and Walsh observed a flatfish at the bottom in 1960, proving vertebrate life exists at the deepest point.
• Sound takes roughly 7 seconds to travel from the surface to the bottom of the Mariana Trench.

Final Thoughts

The Mariana Trench at 10,935 meters represents the absolute depth of Earth's oceans and one of the most extreme environments on the planet. The fact that life persists there — and that human pollution has reached it — tells us something profound about both the resilience of life and the pervasiveness of our impact. The Challenger Deep remains one of the last frontiers of exploration on our own planet.