Tonga Trench
The fastest plate-tectonic velocity on Earth is occurring at this location, as the Pacific plate is being subducted westward in the trench.
It is named for the research vessel Horizon of the Scripps Institution of Oceanography, the crew of which found the deep in December 1952.
A 2016 study found that the abundance of individuals in this community is six times greater than it is at a site on the trench edge at approximately 6,250 m (20,510 ft) near the deep and that the difference in biomass between these locations is even bigger.
[12] Crustal extension in the Miocene Lau-Colville Ridge began at 6 Ma which initiated the opening of the Lau Basin-Havre Trough.
This extension has propagated southward since and has developed into a spreading centre in the Lau Basin in front of the Tonga Trench.
[14] The Pacific crust that descends into the trench is old, 100–140 Ma, and relatively cold and it can therefore store a lot of elastic energy.
[16] Oceanic trenches are important sites for the formation of what will become continental crust and for recycling of material back into the mantle.
[10] The northern end of the Tonga Trench (at 15°10'S) is probably linked to the Fiji fracture zone, trending east–west north of Fiji, but the trench ends in a complex transition from subduction to a strike-slip motion and seismicity patterns indicate a presence of a c. 100 km-broad (62 mi) transition zone rather than a simple transform fault.
The total spreading rate between the Tongan and Australian plates, however, is 157 mm/a (6.2 in/year), and additional microplates and/or deformations zones must thus exist.
These plateaux once formed part of the 100×10^6 km3 (3.5×1018 cu ft) Ontong Java-Manihiki-Hikurangi large igneous province (LIP).
It is a large guyot, 100 km (62 mi) wide at its base with a small part of its reefal or lagoonal summit reaching 440 m (1,440 ft) below sea level.
[28] When the Apollo 13 mission was aborted in 1970 following an explosion in an oxygen tank, it had to bring the entire Lunar Module back to Earth.
As the LEM was jettisoned prior to reentry, its radioisotope thermoelectric generator broke up in the atmosphere, and the heat source plunged into an area of the Pacific Ocean that is either in or near the Tonga Trench.
However, due to protective casing, no release of 238Pu (half-life of 87.7 years) used as heat source in the thermoelectric generator could be detected by atmospheric and oceanic monitoring.
