The Mariana Trench is the deepest oceanic trench on Earth and home to the two lowest points on the planet.
The crescent-shaped trench is in the Western Pacific, just east of the Mariana Islands near Guam. The region surrounding the trench is noteworthy for many unique environments, including vents bubbling up liquid sulfur and carbon dioxide, active mud volcanoes and marine life adapted to pressures 1,000 times that at sea level.
The Challenger Deep, in the southern end of the Mariana Trench (sometimes called the Marianas Trench), is the deepest spot in the ocean. Its depth is difficult to measure from the surface, but in 2010, the National Oceanic and Atmospheric Administration used sound pulses sent through the ocean and pegged the Challenger Deep d at 36,070 feet (10,994 meters). A 2021 estimate using pressure sensors found the deepest spot in Challenger Deep was 35,876 feet (10,935 m). Other modern estimates vary by less than 1,000 feet (305 m).
The Mariana Trench is 1,580 miles (2,542 km) long — more than five times the length of the Grand Canyon. However, the narrow trench averages only 43 miles (69 km) wide.
Because Guam is a United States territory and the 15 Northern Mariana Islands are governed by a U.S. Commonwealth, the U.S. has jurisdiction over the Mariana Trench. In 2009, former President George W. Bush established the Mariana Trench Marine National Monument, which created a protected marine reserve for the approximately 195,000 square miles (506,000 square km) of seafloor and waters surrounding the remote islands. The monument includes most of the Mariana Trench, 21 underwater volcanoes and areas around three islands.
How did the Mariana Trench form?
The Mariana Trench was created by the process that occurs in a subduction zone, where two massive slabs of oceanic crust, known as tectonic plates, collide. At a subduction zone, one piece of oceanic crust is pushed and pulled underneath the other, sinking into the Earth's mantle, the layer under the crust. Where the two pieces of crust intersect, a deep trench forms above the bend in the sinking crust. In this case, the Pacific Ocean crust is bending below the Philippine crust.
The Pacific crust is about 180 million years old where it dives into the trench. The Philippine plate is younger and smaller than the Pacific plate.
As deep as the trench is, it is not the spot closest to the center of Earth. Because the planet bulges at the equator, the radius at the poles is about 16 miles (25 km) less than the radius at the equator. So, parts of the Arctic Ocean seabed are closer to the Earth's center than the Challenger Deep.
The crushing water pressure on the floor of the trench is more than 8 tons per square inch (703 kilograms per square meter). This is more than 1,000 times the pressure felt at sea level, or the equivalent of having 50 jumbo jets piled on top of a person.
Are there volcanoes in the Mariana Trench?
A chain of volcanoes that rise above the ocean waves to form the Mariana Islands mirrors the crescent-shaped arc of the Mariana Trench. Interspersed with the islands are many strange undersea volcanoes.
For example, the Eifuku submarine volcano spews liquid carbon dioxide from hydrothermal vents similar to chimneys. The liquid coming out of these chimneys is 217 degrees Fahrenheit (103 degrees Celsius). At the nearby Daikoku submarine volcano, scientists discovered a pool of molten sulfur 1,345 feet (410 m) below the ocean surface, something seen nowhere else on Earth, according to the National Oceanic and Atmospheric Administration (NOAA).
What lives in the Mariana Trench?
Recent scientific expeditions have discovered surprisingly diverse life in these harsh conditions. Animals living in the deepest parts of the Mariana Trench survive in complete darkness and extreme pressure, said Natasha Gallo, a doctoral student at the Scripps Institution of Oceanography who has studied video footage from filmmaker James Cameron's 2012 expedition into the trench.
Food in the Mariana Trench is extremely limited, because the deep gorge is far from land. Terrestrial plant material rarely finds its way into the bottom of the trench, Gallo told Live Science, and dead plankton sinking from the surface must drop thousands of feet to reach Challenger Deep. Instead, some microbes rely on chemicals, such as methane or sulfur, while other creatures gobble marine life that’s below them on the food chain.
The three most common organisms at the bottom of the Mariana Trench are xenophyophores, amphipods and small sea cucumbers (holothurians), Gallo said.
"These are some of the deepest holothurians ever observed, and they were relatively abundant," Gallo said.
