Mariana Trench facts for kids
The Mariana Trench is the deepest known place in the ocean. It's also the deepest spot on Earth! It's located south and east of the Mariana Islands. This amazing trench goes down about 10,971 meters (that's almost 7 miles!). The western end of the trench is close to Guam.
The trench is super long, about 2,550 kilometers (1,580 miles), but it's pretty narrow, only about 69 kilometers (43 miles) wide on average.
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Name and Origin of the Mariana Trench
The Mariana Trench gets its name from the nearby Mariana Islands. These islands were named Las Marianas in 1668 by Spanish explorers in honor of Queen Mariana of Austria, who was the regent of Spain at the time.
The deep trench and the islands share a close geological connection. The islands are part of a volcanic chain that formed directly because of the plate movements that created the trench itself.
How the Mariana Trench Formed
The Mariana Trench was formed by a geological process called subduction. Earth's outer crust is divided into large pieces called tectonic plates, which float slowly on the hotter layers below. When two plates collide, one plate can slide beneath the other.
In this region, the western edge of the giant Pacific plate collides with the smaller Mariana plate.
Because tectonic plates are constantly grinding against each other, the Mariana subduction zone is active with frequent earthquakes.
Exploration History
The first scientific soundings of the trench took place during the famous Challenger expedition between 1872 and 1876. In 1875, crew members aboard the British ship HMS Challenger dropped a weighted rope into the water and recorded a depth of 4,475 fathoms (8,184 meters; 26,850 feet).
In 1899, the American ship USS Nero used an improved sounding line to record a depth of 5,269 fathoms (9,636 meters; 31,614 feet). While these early mechanical methods were impressive for their time, they were often slightly inaccurate due to ocean currents pulling on the ropes.
In 1951, another British research ship named Challenger II returned to the area. Instead of ropes, scientists used echo sounding, which sends sound waves through the water and measures the time it takes for the echo to bounce back from the seafloor.
The expedition discovered the deepest slot of the trench, which was named the Challenger Deep. They measured a new record depth of 5,960 fathoms (10,900 meters; 35,760 feet). In 1957, the Soviet vessel Vityaz used sonar to explore the area and reported a depth of 11,034 m (36,201 ft; 6,033 fathoms).
In the modern era, multi-beam sonar systems have allowed scientists to create 3D maps of the entire trench floor. In 1984, the Japanese survey vessel Takuyō used multi-beam technology to calculate a depth of 10,924 meters (35,840 ft).
Between 1997 and 2001, scientists from the University of Hawaiʻi mapped the area around Guam. They discovered a second extremely deep pocket, now called the HMRG Deep. In 2011, detailed US Navy surveys mapped the entire trench floor, uncovering four massive underwater mountains called seamounts.
Human and Robotic Descents
Reaching the bottom of the Mariana Trench requires specialized submarines called submersibles. These vessels must have extremely thick hulls made of steel or titanium to prevent them from being crushed by the massive water pressure.
The Historic 1960 Trieste Expedition
The first humans to visit the Challenger Deep were Swiss oceanographer Jacques Piccard and American naval officer Don Walsh. On 23 January 1960, they descended inside the bathyscaphe Trieste, a heavy deep-diving research vessel.
The descent took almost five hours. The crew relied on heavy iron pellets for ballast to pull them down, and lightweight gasoline compartments to provide buoyancy for their return. They spent twenty minutes on the seafloor, measuring a depth of roughly 35,814 feet (10,916 m).
Robotic Exploration by Kaiko and Nereus
Following the Trieste, scientists sent uncrewed remotely operated vehicles (ROVs) to gather high-quality samples:
- In 1995, the Japanese robotic vehicle Kaikō reached the seafloor at 10,911 m (35,797 ft; 5,966 fathoms) and collected mud samples containing living microorganisms.
- In 2009, the hybrid vehicle Nereus spent ten hours exploring the Challenger Deep, capturing video footage and gathering biological specimens.
- In 2020, the Russian autonomous vehicle Vityaz-D carried out the first mission to operate entirely autonomously at the bottom of the trench.
Modern Human Dives and Discoveries
On 26 March 2012, filmmaker and explorer James Cameron made the first solo descent to the Challenger Deep. He designed and piloted the sleek lime-green submersible Deepsea Challenger, descending to a depth of 10,908 m (35,787 ft; 5,965 fathoms) and recording 3D footage of the barren seafloor.
In 2019, American explorer Victor Vescovo made multiple dives into the Challenger Deep aboard the deep-sea submersible DSV Limiting Factor. His dives reached a record depth of 10,928 m (35,853 ft; 5,976 fathoms). In July 2022, deep-sea scientist Dawn Wright became the first Black woman to explore the Challenger Deep. She used side-scan sonar to create detailed geological maps of the Western Pool.
In late 2020, the Chinese crewed submersible Fendouzhe touched down at 10,909 m (35,791 ft; 5,965 fathoms). It later completed more than twenty scientific dives into the deepest trenches of the ocean to collect rock and sediment samples.
Life in the Deep
The environment at the bottom of the trench is one of the most extreme on the planet. Water exerts an immense crushing force of over 1,086 bar (15,750 psi), which is more than 1,000 times the standard atmospheric pressure at sea level. The water is pitch black, and the temperature stays between 1 to 4 °C (33.799999999999 to 39.199999999999 °F)*. But even in this extreme environment, life exists! The HMS Challenger expedition found tiny organisms called radiolaria in samples from the deep.
When the Trieste went down in 1960, its crew thought they saw a type of flatfish on the seabed. However, scientists now think it might have been a sea cucumber. Later, the Kaiko probe's camera spotted a sea cucumber, a scale worm, and a shrimp at the very bottom. The Nereus probe also saw a small polychaete worm.
Scientists also found many simple organisms in the mud samples collected by Kaiko at 10,900 meters (35,760 feet) deep. Most of these were soft-shelled organisms called foraminifera. It's hard for creatures with hard shells made of calcium carbonate to grow at such extreme depths because of the high pressure. This might be why most of the life found there has soft bodies.
Environmental Challenges and Pollution
Even though the Mariana Trench is remote and thousands of meters underwater, human activities have left an impact on this fragile ecosystem.
Plastic Waste and Microplastics
During deep-sea dives, explorers have spotted synthetic trash, including plastic shopping bags and candy wrappers, resting on the seafloor. Because plastic does not biodegrade easily in cold, dark waters, it breaks down into tiny particles called microplastics.
Marine scientists studying amphipods collected from the deepest trenches found that 100% of the examined animals had microplastics in their digestive systems.
Chemical Contaminants
In 2016, researchers discovered high concentrations of toxic man-made chemicals called PCBs in deep-sea scavengers. PCBs were widely used in electrical equipment and paints during the 20th century before being banned due to their environmental risks.
These chemicals stick to sinking organic particles and accumulate in the bodies of deep-sea animals. They reach concentrations fifty times higher than those found in crabs living near heavily polluted rivers.
Interesting Facts About the Mariana Trench
- The Mariana Trench is named after the nearby Mariana Islands. These islands were named "Las Marianas" to honor Queen Mariana of Austria of Spain.
- The deepest point of the trench is more than 2 kilometers (1.2 miles) deeper than the peak of Mount Everest is tall!
- In 2009, the Mariana Trench was made a US National Monument. This helps protect its unique environment.
- As of 2026, four crewed (with man inside) and seven uncrewed vehicles (ROVs, AUVs, and deep-sea landers) have successfully descended to explore the deepest points of the Mariana Trench.
- The first crewed trip to the bottom was by the bathyscaphe Trieste on January 23, 1960. Don Walsh and Jacques Piccard were on board.
Images for kids
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Ocean trenches in the western Pacific
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The bathyscaphe Trieste, the first crewed vehicle to reach the bottom of the Mariana Trench
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See also
In Spanish: Fosa de las Marianas para niños
