sentence: The Pacific plate is subducted above the Mariana Plate, creating the Mariana trench, and (further on) the arc of the Mariana islands, as water trapped in the plate is released and explodes upward to form island volcanoes.
modified: fix grammar:  Pacific plate is subducted above Mariana Plate, creating the Mariana trench, and (further on) the arc of the Mariana islands, as water trapped in the plate is released and explodes upward to form island volcanoes.