Ocean trenches develop in subduction zones at a convergent boundary between two tectonic plates. When a continental plate collides with an oceanic plate the oceanic plate is forced beneath the lighter continental plate. When two oceanic plates meet at a convergent boundary the colder and heavier of the two oceanic plates subducts.
Subduction zone trenches
A trench forms between the two plates in a subduction zone. Trenches are depression in the ocean floor. They are also the deepest part of the seafloor. Trenches form natural boundaries between two tectonic plates. There are 20 major trenches on Earth and 17 of these trenches can be found around the Pacific Ocean Basin. The Mariana Trench contains the Challenger Deep, which is the deepest known place on our planet.
Volcanic mountain ranges form on the continental side of a trench where a continental and an oceanic plate converge. The mountain range is called a volcanic arc. If two oceanic crusts converge an island arc forms on the overriding plate parallel to the trench. Volcanic arcs and island arcs have volcanic mountains that often produce violent volcanic eruptions.
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Ocean Trenches Ocean trenches are found all around the Pacific Ring of Fire. Find out how and why they develop.
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