<P> Xenophyophores have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of 10.6 kilometres (6.6 mi) below the sea surface . On 17 March 2013, researchers from the Scottish Association for Marine Science reported data that suggested microbial life forms thrive within the trench . </P> <P> The Mariana Trench is named for the nearby Mariana Islands (in turn named Las Marianas in honor of Spanish Queen Mariana of Austria, widow of Philip IV of Spain). The islands are part of the island arc that is formed on an over-riding plate, called the Mariana Plate (also named for the islands), on the western side of the trench . </P> <P> The Mariana Trench is part of the Izu - Bonin - Mariana subduction system that forms the boundary between two tectonic plates . In this system, the western edge of one plate, the Pacific Plate, is subducted (i.e., thrust) beneath the smaller Mariana Plate that lies to the west . Crustal material at the western edge of the Pacific Plate is some of the oldest oceanic crust on earth (up to 170 million years old), and is therefore cooler and more dense; hence its great height difference relative to the higher - riding (and younger) Mariana Plate . The deepest area at the plate boundary is the Mariana Trench proper . </P> <P> The movement of the Pacific and Mariana plates is also indirectly responsible for the formation of the Mariana Islands . These volcanic islands are caused by Flux melting of the upper mantle due to release of water that is trapped in minerals of the subducted portion of the Pacific Plate . </P>

What type of plate boundary formed the mariana trench
find me the text answering this question