The Latin word fodĕre , which can be translated as “to dig” , became fossa , which came to our language as a pit . This is what a cavity or excavation is called. Oceanic , for its part, is that linked to the ocean (the sea that separates the continents and that covers a large part of the surface of our planet).
The idea of an oceanic trench , in this framework, refers to a depression in the underwater bottom that is next to the continent or near the coasts of islands of volcanic origin. These sinkholes can have a depth of more than ten kilometers and have water temperatures between 0° C and 2° C.
The Pacific Ocean has the largest number of oceanic trenches and those of greatest depth . Until now, the Mariana Trench is the deepest known ocean trench. It is located southeast of the Mariana Islands , in the northwestern Pacific .
The deepest area of the Mariana Trench is known as the Challenger Deep . Throughout history, several expeditions have been made to explore this place: in 2012 , filmmaker James Cameron reached more than 10,898 meters deep in the Deepsea Challenger submersible.
Ocean trenches are generated when two tectonic plates meet and collide, causing the denser one to slide under the other. This phenomenon , known as subduction , causes the subsidence of the underwater soil: that is, it causes the ocean trench.
The concept of subduction is found within the framework of plate tectonics , a theory of geology that serves to explain the way in which the lithosphere is structured, that is, the rigid layer that covers the surface of our planet. This process in which an oceanic zone of one plate sinks below the boundary of another, takes place in a large number of subduction zones .
Currently, almost all subduction zones are located in the so-called Pacific Ring of Fire , although others can also be found in some regions of the Antilles, the Indian coast of Indonesia and the Mediterranean Sea. It is precisely in these areas that oceanic trenches are formed, where the convergence and collision of two lithospheric plates occurs.
If we take the case of the Peru-Chile trench, also known by the name of the Atacama trench , we are faced with a clear example of the consequence of a collision between two plates: the Nazca oceanic plate (a city located south of Peru). and continental South America.
In the subduction zones where the ocean trenches are located, there is also seismic activity of considerable intensity , which originates from three phenomena carried out by the two plates: friction, compression and tension. All of this usually starts tsunamis and earthquakes in Indonesia and Japan, for example.
When the subducted plate reaches the asthenosphere (the upper part of the mantle found under the lithosphere) it melts and in this state rises to give rise to a volcano . According to the characteristics of each plate, it is possible that the activity gives rise to island arcs (a type of archipelago) or that a mountain range is generated, as is the case of the Sunda Islands and the Mariana Trench. , respectively.
The Tonga Trench , Japan Trench , Kuril Trench , Philippine Trench , and Kermadec Trench are other oceanic trenches more than ten kilometers deep. It should be noted that, despite being so deep, various species live in these graves.