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Mariana Trench Marine National Monument

Explore one of the deepest place on Earth—deeper even than the height of Mount Everest above sea level.

Pacific Islands

Table of Contents

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Underwater hydrothermal-vent chimney
Hydrothermal-vent chimney. In the center of the photo, you can see the vent fluid, which appears as dark smoke due to its high levels of minerals and sulfides. Look closely, and you will also see the chimney is crawling with Chorocaris shrimp and Austinograea wiliamsi crabs. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2016 Deepwater Exploration of the Marianas.

Location and Size

The total area of the Mariana Trench Marine National Monument consists of approximately 95,216 square miles (246,608 square kilometers) of submerged lands and waters of the Mariana Archipelago east of the Philippines. It is comprised of three units:

  • The Islands Unit, which includes the waters and submerged lands of Farallon de Pajaros (also known as Uracus), Maug, and Asuncion (the three northernmost Mariana Islands)
  • The Volcanic Unit or Arc of Fire Refuge, which includes the submerged lands within 1 nautical mile of 21 designated volcanic sites
  • The Trench Unit, which encompasses the submerged lands extending from the northern limit of the Exclusive Economic Zone (EEZ) in the Commonwealth of the Northern Mariana Islands (CNMI) to the southern limit of the EEZ of the United States in the Territory of Guam

The waters above the seafloor in the Volcanic and Trench Units are not included in the Monument. Additionally, the CNMI Government manages the terrestrial environment of Uracus, Maug, and Asuncion.

Management

Established by Presidential Proclamation in January 2009, the Mariana Trench Marine National Monument is cooperatively managed by the Secretary of Commerce (NOAA), the Secretary of the Interior (U.S. Fish and Wildlife Service) and the Commonwealth of the Northern Mariana Islands (CNMI) Government, in cooperation with the Department of Defense and the Department of State.

Monument designation provides international, national, and local recognition that the Marianas is a refuge for seabirds, sea turtles, unique coral reefs, and a great diversity of seamount and hydrothermal vent life worth preservation.

Unique Features

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Jellyfish exploring the Enigma Seamount at 3,700 meters sea deep.
This stunningly beautiful jellying was seen while exploring the Enigma Seamount at 3,700 meters in the Marianas Trench Marine National Monument. Credit: NOAA Office of Exploration & Research (OER), 2016 Deepwater Exploration of the Marianas.

The Mariana Trench Marine National Monument is geologically very complex, sporting a subduction zone, back arc basins, an active simmering island, and submarine volcanoes. 

The crescent-shaped Mariana Trench (part of the Trench Unit) is the "Grand Canyon" of the ocean (actually 120 times larger) and includes some of the deepest known areas on Earth. Challenger Deep, the deepest part of the Mariana Trench and the greater ocean, is located at a depth of about 36,000 feet (around 11,000 meters) — about 7,000 feet deeper than Mount Everest is tall. 

The Volcanic Unit includes a series of undersea mud volcanoes and thermal vents that support unusual life forms in some of the harshest conditions on Earth. Species are able to survive here despite hydrothermal vents that produce highly acidic and boiling water. 

The Champagne vent, found at the NW Eifuku volcano, produces almost pure liquid carbon dioxide (CO2); it’s one of only two known liquid CO2 sites in the world. A pool of liquid sulfur at the Daikoku submarine volcano is also one of a kind — the only other known location of molten sulfur is on Jupiter’s moon Io.

In the Islands Unit, unique reef habitats support marine biological communities dependent on basalt rock foundations, unlike those throughout the remainder of the Pacific. These reefs and waters are among the most biologically diverse in the Western Pacific and include some of the greatest diversity of seamount and hydrothermal vent life yet discovered. They also contain one of the most diverse collections of stony corals in the Western Pacific. 

The submerged caldera (volcanic crater) at Maug is one of only a few known places in the world where photosynthetic and chemosynthetic communities (those that make food from light and inorganic chemicals, respectively) co-exist. The caldera is approximately 1.5 miles (2.4 kilometer) wide and 820 feet (250 meter) deep, with very steep inner walls. In the center of the crater, a coral-topped lava dome rises to within 65 feet (20 meter) of the surface, while deep hydrothermal vents along the northeast side of the dome emit low-temperature water that influences the deep-water composition. Shallow warm water and gas vents near the mid-point of the inner East Island have a localized negative impact on the otherwise thriving coral reef system at Maug. Volcanic vents within the caldera provide scientists with an in situ (in the field) laboratory for the changes that will likely occur in coral reef ecosystems from ocean acidification and rising water temperatures associated with global warming.

Elsewhere within the Islands Unit, coral reef ecosystems have high numbers of apex predators (sharks and jacks), larger than anywhere else along the Mariana Archipelago, with one site having the highest density of sharks anywhere in the Pacific. Similarly, these northern islands have the highest large fish biomass (total mass of fish in a given volume) in the Mariana Islands. The rare bumphead parrotfish (the largest parrotfish species), lives in these waters.

Looking to the Future

This vast and unique area is perhaps the most spectacular part of the Ring of Fire that encircles most of the Pacific Ocean. It has many secrets to yield and many potentially valuable lessons that can benefit the rest of the world. 

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Remotely operated vehicle underwater at Chamorro Seamount.
ROV Deep Discoverer images a newly discovered hydrothermal vent field at Chamorro Seamount. Credit: NOAA OER, 2016 Deepwater Exploration of the Marianas.

NOAA research expeditions will continue to study and explore this amazing area. NOAA Fisheries and the U.S. Fish and Wildlife Service are working with the CNMI Government, Department of Defense, Department of State, U.S. Coast Guard, and others to develop a monument management plan and are collaborating for the long-term protection of the Marianas. 

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Last updated by Pacific Islands Regional Office on 05/20/2024