island arc is a line of volcanoes on an oceanic plate.
island arc is a line of volcanoes on an oceanic plate.
which arc is a line of volcanoes on an oceanic plate?
island arc
Na
Na
the width of the plate determines whether the divergent double subduction can be sustained. the inverted "u" shape of the oceanic plate is not an effective geometry for it to sink because of the mantle materials beneath. those mantle materials need to escape by toroidal flow at the edge of the subducted oceanic plate. with a narrow oceanic plate (width  2000 km), the trapped mantle beneath the oceanic plate can effectively escape by toroidal flow. in contrast, for a persistent oceanic plate (width  2000 km), the trapped mantle beneath the oceanic plate cannot escape effectively by toroidal flow and the system cannot be sustained. therefore, divergent double subduction can only occur in small narrow oceanic plate but not in large width oceanic plate. this also explains why it is rare in nature and most subduction zones are single sided.
divergent double subduction