Mariana Trench
The deepest ocean trench on Earth, reaching about 10,935 m at Challenger Deep, formed where the Pacific Plate dives beneath the Mariana Plate.
Subduction: The sinking of one tectonic plate beneath another into the mantle, producing trenches, volcanoes and deep earthquakes. The trench is the surface scar of the subduction zone that consumes the Pacific seafloor.
Challenger Deep: The deepest surveyed point of the Mariana Trench and of the ocean, about 10,935 m below sea level. The trench's deepest point, where every descent record has been set.
Jacques Piccard: Swiss engineer and oceanographer who co-piloted Trieste to the floor of Challenger Deep in 1960. He co-designed the bathyscaphe and made the trench's first bottom descent.
Plate tectonics: The theory that Earth's moving plates interact at boundaries, driving earthquakes, volcanism and mountain building. The framework explaining why the trench exists where it does and how deep it can grow.
Tonga Trench: The South Pacific trench with Earth's fastest plate convergence and a maximum depth near 10,800 m. The other Pacific end-member of fast subduction, often compared with the Mariana system.
Pacific Plate: The largest tectonic plate, whose old, cold, dense oceanic crust sinks steeply into the mantle beneath the western Pacific. Its great age makes it unusually dense, driving the steep descent that deepens the trench.
Trieste (bathyscaphe): The Piccard-designed bathyscaphe that made the first manned descent to the seafloor of Challenger Deep in 1960. The vessel of the first successful dive to the trench floor.
Don Walsh: American naval officer who co-piloted Trieste with Piccard on the 1960 Challenger Deep dive. The other occupant of the first crewed dive to the trench floor.
Seafloor spreading: The creation of oceanic crust at mid-ocean ridges as plates diverge, aging and cooling as it moves away. The process that produced the old, dense Pacific crust now sinking at the trench.
Puerto Rico Trench: The Atlantic's deepest trench, about 8,376 m, where the North American Plate underthrusts the Caribbean Plate. An Atlantic subduction trench that is far shallower because its crust is younger and less dense.