Oceanic Trench
An oceanic trench is a significant geological feature characterized by a deep depression in the ocean floor, formed through the collision of tectonic plates. These trenches can be several miles wide and thousands of feet deep, often found in all oceans but predominantly in the Pacific Ocean. The formation process involves one tectonic plate sliding beneath another, creating a subduction zone and leading to extreme conditions such as immense pressure and near-freezing temperatures at the bottom. Despite the harsh environment, specialized life forms have adapted to thrive in these trenches, displaying unique characteristics like bioluminescence and translucent bodies to survive in darkness and cope with the high-pressure conditions.
The deepest known point, the Challenger Deep in the Mariana Trench, plunges over 36,000 feet below sea level and has been explored by both manned and unmanned vessels. Notable explorations include the Trieste in 1960, which first proved life existed in these depths, and James Cameron's solo dive in 2012, which advanced our understanding of these mysterious ecosystems. Oceanic trenches not only serve as a vital habitat for deep-sea organisms but also provide insights into geological processes and the limits of life on Earth.
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Oceanic Trench
Anoceanic trench is a massive depression in the ocean floor. Many oceanic trenches are several miles wide and thousands of feet deep. They are formed when the tectonic plates beneath the ocean collide, causing a portion of the ocean's floor to sink beneath Earth's crust.
Trenches create an oceanic environment that is extremely harsh. Only life forms that have evolved to live in such an environment can survive. The immense pressure at the bottom of the ocean would crush most aquatic creatures. Additionally, the water in oceanic trenches is just above freezing temperatures, too cold for most ocean life.
Background
Oceanic trenches are formed through interactions between tectonic plates, which are massive slabs of rock that stretch beneath Earth's crust. They are composed of a variety of minerals that allow them to float on top of the magma beneath them. Tectonic plates are constantly moving, causing them to grind against each other. In some cases, plates move in large lurches, causing earthquakes.
Oceanic trenches are formed when tectonic plates collide. The lighter plate moves over the denser, heavier plate, pushing it deeper into the earth, a process called sublimation. As the heavier plate slowly moves down into the molten layer beneath it, it carries chunks of the ocean floor with it. These chunks are then fed into the molten rock beneath Earth's crust, which destroys them and removes old sediment from the ocean floor.
Over many years, sublimated areas cause the ocean floor above them to sink into the massive trenches. In many cases, oceanic trenches fill with sediment faster than the sublimation process can consume it. A trench filled with sediment is invisible to the naked eye and can only be detected with specialized equipment.
Overview
Unfilled oceanic trenches are major features of the ocean landscape. Many are tens of miles wide and hundreds of miles long. They can be found in every ocean, though the deepest oceanic trenches are in the Pacific Ocean. The Ring of Fire, an area of intense volcanic activity in the Pacific Ocean, has caused the trenches within its borders to become deeper than any others.
Oceanic trenches can sink to more than three times the depth of the rest of the ocean. The deepest known point in the ocean, the Challenger Deep, is at the bottom of the Mariana Trench. The Challenger Deep is more than 36,000 feet below sea level. It was first discovered in 1951 by the British Royal Navy ship the HMS Challenger, which was measuring the ocean floor.
Oceanic trenches are not a suitable environment for most oceanic life. The pressure at the bottom of the ocean can reach more than one thousand times that of the surface. The water is so deep that almost no light reaches the bottom, and temperatures can vary from extremely cold in the darkest areas to searing hot near the thermal vents. However, despite the inhospitable traits of the trenches, many specialized forms of life have evolved to thrive there.
Many creatures in the dark trenches create their own light. Specialized cells and chemical reactions in their bodies cause a phenomenon called bioluminescence. Bioluminescent creatures glow brightly under certain conditions. Some use their bioluminescence as bait, drawing confused fish to their light. Others use it to attract and communicate with mates. Other sea creatures have evolved to become translucent, which makes them invisible in the dark. They use this feature to hide from predators.
Some sea creatures that are native to oceanic trenches have evolved to have incredibly large eyes, which allow them to make the most of the small amounts of light available to them. Still other creatures evolved to be able to navigate without using sight. Sea creatures in trenches must also be able to adapt to the crushing pressure and cold temperature. They have developed special ways to store fat to stop their cells from freezing and skeletal structures that thrive in intense pressure.
Though it was long thought impossible, humans have traveled to the bottom of the Mariana Trench. On January 23, 1960, scientists Don Walsh and Jacques Piccard entered their specialized submarine, the Trieste. The Trieste was a bathyscaphe, a submarine designed to withstand the intense pressure of the deep ocean. It had a spherical room attached to its bottom, created for observing ocean life. It was equipped with a variety of precise instruments to carry out experiments at the bottom of the ocean.
It took the Trieste more than five hours to dive to the bottom of the Challenger Deep. However, as soon as they arrived, the scientists realized that the Trieste's descent had knocked silt loose from the ocean floor, severely limiting their visibility. They had a narrow window of just twenty minutes to study their surroundings—but during that time, Jacques Piccard witnessed a sea cucumber on the ocean floor, showing the world for the first time that life could exist in such an inhospitable place. With proof of life in hand, the scientists successfully returned to the surface.
In the early twenty-first century, scientists began to send unmanned vessels to the bottom of the ocean. These vessels could stay underwater longer than their manned counterparts and did not risk lives if they failed. These submersibles found many new species surviving in the trenches, photographed them, and allowed scientists to catalog them.
In 2012, explorer James Cameron became the third person to reach the depths of an oceanic trench. He traveled in a single-person submersible, the Deepsea Challenger, which dived to the bottom of the Challenger Deep. Cameron broke the record for the deepest solo dive ever. The Deepsea Challenger collected samples from the bottom of the oceanic trench, giving scientists valuable insight into the exotic ecosystem. However, in 2019, regular dives in the DSV Limited Factor began. This is deep-submersion vehicle. By 2022, DSV Limited Factor had made 115 dives to the Challenger Deep. In 2020, Kathryn Sullivan, an astronaut, and Vanessa O'Brien, a mountaineer, became the first women to dive to Challenger Deep.
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