The Ocean trenches Are abysses in the seabed that are formed as a result of the activity of the tectonic plates of the Earth, that when converging one is pushed underneath the other.
These long, narrow V-shaped depressions are the deepest parts of the ocean and are found all over the world reaching depths of about 10 kilometers below sea level.
In the Pacific Ocean are the deepest pits and form part of the so-called"Ring of Fire"which also includes active volcanoes and earthquake zones.
The deepest ocean trench is the Marianas Trench located near the Marine Islands with a length of more than 1,580 miles or 2,542 kilometers, 5 times longer than the Grand Canyon in Colorado, United States and on average has only 43 miles ( 69 kilometers) wide.
There is located the Abyss Challenger that with 10,911 meters is the deepest part of the ocean. Also, the graves of Tonga, Kuriles, Kermadec and the Philippines are more than 10,000 meters deep.
In comparison, Mount Everest has a height of 8,848 meters above sea level, which means that the Marianas Trench in its deepest part is more than 2,000 meters deep.
The ocean trenches occupy the deepest layer of the ocean. The intense pressure, lack of sunlight and the frigid temperatures of this place make it one of the most unique habitats on Earth.
How do oceanic graves form?
The pits are formed by subduction, a geophysical process in which two or more Earth's tectonic plates converge and the oldest and denser is pushed under the lighter plate causing the sea floor and the outer crust (the lithosphere) Curve and form a slope, a V-shaped depression.
Subduction Zones
In other words, when the edge of a dense tectonic plate meets the edge of a less dense tectonic plate, the denser plate is curved downwards. This type of boundary between layers of the lithosphere is called convergent. The place where the denser plate is subducted is called the subduction zone.
The subduction process makes the trenches a dynamic geological feature, accounting for a significant part of Earth's seismic activity and often the epicenter of major earthquakes, including some of the earthquakes with the highest magnitude recorded.
Some ocean trenches are formed by subduction between a plate bearing a continental crust and a plate bearing an oceanic crust. The continental crust always floats more than the oceanic crust and the latter will always be subducted.
The well-known ocean trenches are the result of this boundary between converging plates. The Peru-Chile Fossil of the west coast of South America is formed by the oceanic crust of the Nazca plate that is subducted under the continental crust of the South American plate.
The Ryukyu Trench which extends from southern Japan, is formed in such a way that the oceanic crust of the Philippine plate is subducted under the continental crust of the Eurasian plate.
Rarely ocean trenches can form when two plates bearing continental crust meet. The Marianas Trench, in the South Pacific Ocean, forms when the imposing Pacific plate is subducted under the smallest and least dense plate of the Philippines.
In a subduction zone, some of the molten material, which was previously the sea floor, is usually raised through volcanoes located near the pit. Volcanoes often create volcanic arches, a mountainous island that lies parallel to the pit.
The Aleutian Fosa is formed where the Pacific plate is subducted under the American plate in the Arctic region between the state of Alaska in the United States and the Russian region of Siberia. The Aleutian Islands form a volcanic arc that leaves the peninsula of Alaska and just north of the Aleutian Fosa.
Not all oceanic graves are in the Pacific. The Puerto Rico Trench is a complex tectonic depression that is in part formed by the subduction zone of the Lesser Antilles. Here, the oceanic crust of the huge North American plate is subducted under the oceanic crust of the smallest Caribbean plate.
Why are oceanic graves important?
Knowledge of ocean trenches is limited because of their depth and the remoteness of their location, but scientists know that they play a significant role in our life on the mainland.
Much of the world's seismic activity takes place in subduction zones, which can have a devastating effect on coastal communities and even more so on the global economy.
Soil earthquakes generated in subduction zones were responsible for the Indian Ocean tsunami in 2004 and the Tohoku earthquake and tsunami in Japan in 2011.
By studying the ocean trenches, scientists can understand the physical process of subduction and the causes of these devastating natural disasters.
The study of the pits also gives researchers the understanding of the novel and diverse ways of adapting organisms from the depths of the sea to their environment, which may contain the key to biological and biomedical advances.
Studying how deep sea organisms have adapted to life in their harsh environments can help advance understanding in many different areas of research, from diabetes treatments to improved detergents.
Researchers have already discovered microbes that inhabit hydrothermal vents in the sea abyss that have potential as new forms of antibiotics and drugs for cancer.
Such adaptations may also contain the key to understanding the origin of life in the ocean as scientists examine the genetics of these organisms to construct the puzzle of how life expands between isolated ecosystems and eventually through The oceans of the world.
Recent research has also revealed unexpected and large amounts of coal material accumulated in the trenches, which could suggest that these regions play a significant role in the Earth's climate.
This coal is confiscated in the mantle of the Earth through subduction or consumed by bacteria from the pit.
This discovery presents opportunities for further research into the role of graves as both a source (through volcanoes and other processes) and as a reservoir in the planet's carbon cycle that can influence how scientists eventually understand and predict The impact of greenhouse gases generated by humans and climate change.
The development of new deep sea technology, from submersibles to cameras and sensors and samples, will provide great opportunities for scientists to systematically investigate the ecosystems of the trenches for long periods of time.
This will eventually give us a better understanding of earthquakes and geophysical processes, review how scientists understand the global carbon cycle, provide avenues for biomedical research, and potentially contribute to new insights into the evolution of life on Earth.
These same technological advances will create new capabilities for scientists to study the ocean as a whole, from remote coastal lines to the ice-covered Arctic Ocean.
Life in the ocean trenches
The ocean trenches are among the most hostile habitats on earth. The pressure is more than 1,000 times relative to the surface and the water temperature is slightly above the freezing point. Perhaps more importantly, sunlight does not penetrate deeper ocean trenches, making photosynthesis impossible.
The organisms that live in the ocean trenches have evolved with unusual adaptations to develop in these cold and dark canyons.
Their behavior is a test of the so-called"visual interaction hypothesis"which says that the greater the visibility of an organism, the more energy it must expend to hunt a prey or repel predators. In general, life in the dark oceanic graves is isolated and in slow motion.
Pressure
The pressure at the bottom of the Abyss Challenger, the deepest place on earth, is 703 kilograms per square meter (8 tons per square inch). Large marine animals such as sharks and whales can not live in this crushing depth.
Many organisms that develop in these high pressure environments do not have organs that are filled with gases, like the lungs. These organisms, many related to starfish or jellyfish, are made mostly of water and gelatinous material that can not be crushed as easily as the lungs or bones.
Many of these creatures navigate the depths well enough to make a vertical migration of more than 1,000 meters from the bottom of the pit each day.
Even the fish in the deep pits are gelatinous. Many species of snail fish with bulb head, for example, live in the bottom of the Trench of the Marianas. The bodies of these fish have been compared with disposable handkerchiefs.
Dark and deep
Shallow ocean trenches have less pressure, but may still be outside the area of sunlight, where light penetrates the water.
Many fish have adapted to life in these dark oceanic graves. Some use bioluminescence, meaning that they produce their own light to live in order to attract their prey, find mate or repel the predator.
Food nets
Without photosynthesis, marine communities depend primarily on two unusual sources of nutrients.
The first is"marine snow". Marine snow is the continuous fall of organic material from the heights in the water column. Marine snow is mainly waste, including excrement and the remains of dead organisms such as fish or seaweed. This nutrient-rich marine snow feeds animals such as sea cucumbers or vampire squids.
Another source of nutrients for food webs in oceanic trenches comes not from photosynthesis but from chemosynthesis. Chemosynthesis is the process in which organisms in the oceanic pit, such as bacteria, convert chemical compounds into organic nutrients.
The chemical compounds used in chemosynthesis are methane or carbon dioxide expelled from hydrothermal vents that release their toxic and hot gases and fluids into the frigid ocean water. A common animal that relies on chemosynthesis bacteria to obtain food is the giant tube worm.
Exploring the graves
The ocean trenches remain as one of the most elusive and little-known marine habitats. Until 1950, many oceanographers thought these pits were unchanging environments close to being devoid of life. Even today, much of the ocean trench research is based on samples of seafloor and photographic expeditions.
That is slowly changing as explorers dig deep, literally. The Challenger Abyss, deep in the Marianas Trench, lies deep in the Pacific Ocean near the island of Guam.
Only three people have visited the Abyss Challenger, the world's deepest ocean trench: a joint Franco-American crew (Jacques Piccard and Don Walsh) in 1960 reaching a depth of 10,916 meters and the National Geographic James Cameron's explorer in residence in 2012 Reaching 10,984 meters (Two other unmanned expeditions have also explored the Abyss Challenger).
The engineering of submersibles to explore the ocean trenches presents a great set of unique challenges.
The submersibles must be incredibly strong and resistant to combat with strong ocean currents, zero visibility and great pressure from the Marianas Trench.
Developing engineering to transport people safely, as well as delicate equipment, is still a major challenge. The submarine that took Piccard and Walsh to Abyss Challenger, the extraordinary Trieste, was an unusual vessel known as the bathyscaph (submarine to explore the depths of the ocean).
Cameron's submersible, Deepsea Challenger, successfully addressed engineering challenges in innovative ways. To combat deep ocean currents, the submarine was designed to rotate slowly while descending.
The lights on the submarine were not bulbs incandescent or fluorescent, but arrangements of tiny LEDs that illuminated an area of about 30 meters.
Perhaps more surprisingly, the Deepsea Challenger itself was designed to be compressed. Cameron and his team created a synthetic glass-based foam that allowed the vehicle to squeeze under the pressure of the ocean. The Deepsea Challenger returned to the surface 7.6 centimeters smaller than when it descended.
References
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