Ocean trenches are long, narrow depressions on the seafloor. These trenches are the deepest parts of the ocean - and some of the deepest natural spots on Earth. Ocean trenches are found in every ocean basin on the planet, although the deepest ocean trenches are found in the Pacific as part of the so-called “Ring of Fire” that also includes active volcanoes and earthquake zones. Oceanic Trench Location Romanche ​The Romanche Trench, also called the Romanche Gap, is the third deepest of the major trenches of the Atlantic Ocean, after the Puerto Rico Trench and the South Sandwich Trench. It bisects the Mid-Atlantic Ridge just north of the equator at the narrowest part of the Atlantic between Brazil and West Africa, extending from 2°N to 2°S and from 16°W to 20°W. The trench has been formed by the actions of the Romanche Fracture Zone, a portion of which is an active transform boundary offsetting sections of the Mid-Atlantic Ridge Swire In the dark abyss of the Mariana Trench in the western Pacific lies the deepest spot in the world's oceans and the deepest-dwelling fish ever discovered with verified depth. Large numbers of the new species were attracted to traps baited with mackerel. Pseudoliparis swirei is a small, tadpole-like fish measuring a little over four inches in length (112 mm) yet appears to be the top predator in its benthic community at the bottom of this particularly deep sea. Sunda It is earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian-Capricorn plates subduct under a part of the Eurasian Plate. Its maximum depth is the deepest point in the Indian Ocean. The trench stretches from the Lesser Sunda Islands past Java, around the southern coast of Sumatra on onto the Andaman Islands, and forms the boundary between Indo-Australian Plate and the Eurasian plate. The trench is considered to be part of the Pacific Ring of Fire as well as one of a ring of oceanic trenches around the northern edges of the Australian Plate. Challenger The lowest point of the Pacific Ocean is Challenger Deep in the Mariana Trench.