The Tonga Trench is located in the South Pacific Ocean and is 10,882 metres (35,702 ft) deep at its deepest point, known as the Horizon Deep.
The Tonga Trench is a convergent plate boundary. The trench lies at the northern end of the Kermadec-Tonga Subduction Zone, an active subduction zone where the Pacific Plate is being subducted below the Tonga Plate and the Indo-Australian Plate. The Tonga Trench extends north-northeast from the Kermadec Islands north of the North Island of New Zealand. The trench turns west north of the Tonga Plate and becomes a transform fault zone.
The convergence is taking place at a rate estimated at approximately 15 centimetres (6 in) per year (by Lonsdale, 1986); however, recent Global Positioning Satellite measurements indicate in places a convergence of 24 centimetres (9 in) per year across the northern Tonga Trench, which is the fastest plate velocity recorded on the planet; a result is the earth's most active zone of mantle seismicity.[1] Such oceanic trenches are important sites for the formation of what will become continental crust and for recycling of material back into the mantle. Along the Tonga Trench mantle-derived melts are transferred to the island arc systems, and abyssal oceanic sediments and fragments of oceanic crust are collected.
The trench is the last resting place of the radioisotope thermoelectric generator from the aborted Apollo 13 mission.