Ocean trenches are deep depressions in the ocean floor that form at subduction zones where lithospheric plates meet. The Mariana Trench is the deepest point on Earth, and aquatic life thrives in these extreme environments.
Ocean trenches are chasms or depressions in the ocean floor. They are usually narrow but extremely deep, reaching some of the lowest points below sea level ever discovered. These trenches form in subduction zones, which mark lithospheric plate boundaries.
The lithospheric layer of the Earth includes the upper mantle and the crust, or surface. All of the planet’s water and land are found on the lithosphere. This layer is not a whole mass, but a congregation of several slabs, called plates. These plates are huge and can be the foundation of entire oceans and continents. The study of these lithospheric plates and their motion is called plate tectonics, one of the main theoretical fields of geology.
There are three main types of boundaries where these plates meet. Transformation boundaries are where plates move relative to each other, divergent boundaries are where plates move away from each other, and convergent boundaries are where one plate slides under the other. Oceanic trenches form at convergent boundaries, called subduction zones, which are usually the center of much tectonic activity.
Trenches in the ocean are commonly found parallel to volcanic islands. This is often due to dehydration reactions, which occur when an underlying plate sinks under the upper one. This motion often causes water to contact the hot mantle from beneath the lithosphere, and the resulting chemical reaction creates a landmass. Volcanoes and volcanic island chains, called volcanic arcs, form when lava is released and accumulates above the waterline.
The Mariana Trench, located near Japan in the Pacific Ocean, is the deepest ocean trench. It is also the deepest point on the earth’s surface, reaching a depth of 36,201 feet (11,033 meters). That means it’s larger than the highest point on Earth, Mount Everest, which measures 29,035 feet (8,850 meters). The deepest point of the Mariana Trench, called Challenger Deep, is named after HMS Challenger II, the British exploration vessel that first reached that depth in 1960.
Aquatic life also thrives in these trenches, which are devoid of almost any kind of light and subjected to extreme pressures. Numerous different species have been found in them, ranging from microorganisms such as bacteria to jellyfish, lobsters and octopuses. A soil sample taken from the Challenger Deep even showed signs of foraminifera, which are single-celled organisms that resemble some of the earliest life forms discovered on Earth.
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