Mariana trench? Deep Sea Challenge

The Mariana Trench is a crescent-shaped trench in the Western Pacific, just east of the Mariana Islands near Guam. The region surrounding the trench is noteworthy for many unique environments. The Mariana Trench contains the deepest known points on Earth, 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 modern estimates vary by less than 1,000 feet (305 meters).

In 2010, the Challenger Deep was pegged at 36,070 feet (10,994 m), as measured with sounds pulses sent through the ocean during a 2010 survey by the National Oceanic and Atmospheric Administration (NOAA).

In 2012, film director and deep-sea explorer James Cameron descended to the bottom of Challenger Deep, briefly reaching 35,756 feet (10,898 m) during the 2012 expedition. But he could have gone a little deeper. A high-resolution seafloor mapping survey published in 2014 by researchers from the University of New Hampshire said the Challenger Deep bottoms out at 36,037 feet (10,984 m)
The ocean's second-deepest place is also in the Mariana Trench. The Sirena Deep, which lies 124 miles (200 kilometers) to the east of Challenger Deep, is a bruising 35,462 feet deep (10,809 m).

By comparison, Mount Everest stands at 29,026 feet (8,848 m) above sea level, meaning the deepest part of the Mariana Trench is 7,044 feet (2,147 m) deeper than Everest is tall.

Protected land
The Mariana Trench is 1,580 miles (2,542 kilometers) 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 U.S. territory and the 15 Northern Mariana Islands are a U.S. Commonwealth, the United States has jurisdiction over the Mariana Trench. In 2009, 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. It includes most of the Mariana Trench, 21 underwater volcanoes and areas around three islands.
How the trench formed
The Mariana Trench was created by the process that occurs in a subduction zone, where two massive slabs of oceanic crust 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. [Infographic: Tallest Mountain to Deepest Ocean Trench]

The Pacific crust, also called a tectonic plate, is about 180 million years old where it dives into the trench. The Philippine plate is younger and smaller than the Pacific plate.

"At subduction zones, the cold, dense crust sinks back into the mantle and is destroyed," said Nicholas van der Elst, a seismologist at Columbia University's Lamont Doherty Earth Observatory in Palisades, New York.

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.

Mariana trench? Deep Sea Challenge
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