Explanation:

Oceanic trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression. This process makes trenches dynamic geological features—they account for a significant part of Earth’s seismic activity—and are frequently the site of large earthquakes, including some of the largest earthquakes on record.
Subduction also generates an upwelling of molten crust that forms mountain ridges and volcanic islands parallel to the trench. Examples of these volcanic "arcs" can be seen in the Japanese Archipelago, the Aleutian Islands, and many other locations around this area called the Pacific "Ring of Fire."
Trenches are long, narrow and very deep and, while most are in the Pacific Ocean, can be found around the world. The deepest trench in the world, the Mariana Trench located near the Mariana Islands, is 1,580 miles long and averages just 43 miles wide. It is home to the Challenger Deep, which, at 10,911 meters (35,797 feet), is the deepest part of the ocean. The Tonga, Kuril-Kamatcha, Philippine, and Kermadec Trenches all contain depths greater than 10,000 meters (33,000 feet).
Mariana trench is the deepest trench followed by the Tonga trench. (Challenger deep is a part of Mariana trench)