Mariana Trench
The Mariana Trench, located in the western Pacific Ocean just east of the Mariana Islands, is the deepest known point in Earth's oceans, reaching depths of approximately 36,070 feet (10,994 meters) at its deepest point, known as Challenger Deep. This crescent-shaped trench spans about 1,580 miles (2,543 km), making it five times longer than the Grand Canyon. Formed by the interaction of the Pacific and Philippine Sea tectonic plates, the trench is situated in a geologically active area prone to earthquakes. Despite the extreme pressures and lack of light at such depths, the trench hosts unique ecosystems, including various life forms such as microbes, amphipods, and foraminifera, some of which thrive near underwater mud volcanoes that can reach high temperatures. Scientific exploration of the trench has a rich history, beginning with the H.M.S. Challenger expedition in 1875 and continuing with more recent descents by researchers and explorers. Studies in the trench have revealed new species and significant discoveries, such as evidence of plastic pollution, and have provided insights into the origins of life and geological processes on Earth. The Mariana Trench is also protected as part of the US Marianas Trench Marine National Monument, underscoring the importance of preserving this unique and fragile environment.
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Mariana Trench
The Mariana Trench (also known as the Marianas Trench) is an underwater indentation in Earth's crust that marks the deepest point in any of the world's oceans. This crescent-shaped groove is located in the western Pacific Ocean just east of the Mariana Islands, a chain of islands that includes the American dependencies of the Northern Mariana Islands and Guam. Because of this, the Mariana Trench falls under US jurisdiction. Since 2009, it has been protected as part of the US Marianas Trench Marine National Monument.
The Mariana Trench is immense—it is 1,580 miles (2,543 km) long. This is five times longer than the Grand Canyon. The deepest known point, called Challenger Deep, reaches at least 36,070 feet (10,994 m)—or almost seven miles—below sea level. For comparison, Mount Everest, which is the highest point on Earth, only rises 29,026 feet (8,847 m) above sea level.
Despite its great depth, the Mariana Trench is known to host a variety of life-forms capable of living in these extreme ecosystems, including some species of bacteria, microbes, xenophyophores, amphipods, and foraminifera.
Background
The Mariana Trench is located at 17.7500° N, 142.5000° E. It was formed through the interactions between parts of Earth's shell called tectonic plates. These plates are composed of the crust and pieces of Earth's upper mantle. Places where tectonic plates rub against each other are often seismically active, meaning that they are more likely to have earthquakes. Trenches are created at the boundaries of these plates, through a process related to how earthquakes occur. When two boundary plates push against each other, one of them (called the downgoing plate) may be forced down by the second plate (known as the overriding plate) at a geologic location called a subduction zone. The downgoing plate becomes bent and is thrust downward into the mantle of Earth, thus creating a trench. In the case of the Mariana Trench, the downgoing plate is the Pacific Plate, while the overriding plate is the Philippine Sea Plate.
Over time, the interactions between these two plates has caused the Pacific Plate to be pushed further east. However, the northern and southern ends of this plate are fixed into place where they intersect with the Ogasawara Plateau to the north and the Caroline Ridge to the south. As a result, the Mariana Trench is like a stick being bent in the middle; it has assumed its characteristic curved shape as its tips remained pinned and the center is slowly moved eastward.
This movement has resulted in several other geological oddities in the region. For instance, the disruptive motion of the tectonic plates has left faults throughout the region to its west, leaving it prone to regular earthquakes. These movements additionally cause the downgoing plate to release fluids because of heightened pressure and temperatures. These fluids interact with nearby mantle materials to create massive underwater mud volcanoes that can be as big as 30 miles (48 km) in diameter and 6,562 feet (2,000 m) tall. Fluids leak from these volcanoes, creating rich and unique ecosystems.
The Mariana Trench was first explored in 1875 by the H.M.S. Challenger, a ground-breaking British oceanographic expedition. Using a weighted sounding rope, scientists charted a depth of almost 5 miles (8 km) deep. In 1951, a follow-up expedition by the H.M.S.Challenger II used an echo sounder to measure a depth of 7 miles (11 km). The Mariana Trench also contains the second-deepest point in the ocean—Sirena Deep, which reaches a depth of 35,462 feet (10,809 m) below sea level.
Several successful descents into the Challenger Deep (named after the oceanography vessel) have been achieved. In 1960, Jacques Piccard and Don Walsh became the first humans to reach the bottom of Challenger Deep when they accomplished the feat in a Navy submersible called the Trieste. Famed film director James Cameron traveled into Challenger Deep in 2012 in a specially crafted submersible called the Deepsea Challenger. In 2019, Victor Vescovo made the deepest crewed submersible dive into the trench up to that point, reaching 35,853 feet (10,927 m), as part of the Five Deeps expedition.
Overview
Several unique ecosystems have been discovered in the various harsh environs of the Mariana Trench. The extreme depths of this habitat mean that no light penetrates into its depths. Life-forms have additionally been forced to adjust to intense water pressures and a lack of nutrients. Some regions near the mud volcanoes and vents are subject to extreme heat up to 572° F (300° C), although most deep sea zones are typically prone to temperatures near freezing. This type of deep sea environment is called a hadal or hadopelagic zone, names which are meant to invoke Hades, the Greek god of the underworld. Hadal zones occur at between 20,000 to 36,000 feet (6,000 to 11,000 meters). The next-deepest region of the ocean is called the abyssal or abyssopelagic zone, which occurs between 13,123 to 19,685 feet (4,000 to 6,000 meters) below sea level.
Expeditions into the Mariana Trench have shown species of animals living at depths that were previously thought impossible. For instance, one Mariana Trench expedition discovered a species of snailfish, a type of translucent, scaleless fish with gelatinous-appearing skin from the Liparidae family, living at 26,715 feet (8,143 meters) below sea level—the deepest depth a fish had ever been recorded. As studies of the area continued, in 2023 an expedition collected a type of virus from the trench that was believed to be the deepest bacteriophage virus ever found. At the same time, expeditions had also found evidence of plastic pollution.
In Challenger Deep, scientists discovered more than four hundred species of foraminifera, a type of single-cell, soft-shelled protist. Protists are a form of organism that are taxonomically distinct from all animals, plants, and fungi. Scientists believe they may resemble the first types of life to have evolved on Earth. In particular, samples taken showed a higher concentration of tube-shaped foraminifera, which represented 85 percent of all accounted species. It is believed that these species are able to survive, in part, on debris that falls from above, as the ecosystem is otherwise very nutrient poor. A lack of predators may have allowed these protists to proliferate. Studying these extreme environments has allowed scientists to speculate about how life originally evolved in what was likely a similarly hostile environment millions of years ago. Studies of rock samples recovered from Challenger Deep may help scientists to understand how the geology of the ocean floor and the Mariana Islands developed.
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