Question

when oceanic crust and continental crust converge at a subduction zone, which plate is most likely to be subducted and why?

Answer 1

In a subduction zone, when an oceanic lithospheric plate converges with a continental lithospheric plate, the oceanic plate gets subducted under the continental plate. This is because the oceanic plate has a higher density than the continental plate. Lithologically, The continental crust consists of various layers, with a bulk composition that is intermediate (SiO₂ wt% = 60.6). The average density of continental crust is about 2.83 g/cm³. The oceanic crust has an average density of 3.3 g/cm³ and is mainly made up of mafic and ultramafic composition i.e. the upper oceanic crust usually consists of pillow lavas and discordant intrusive igneous complexes, and the lower oceanic crust is composed of troctolite, gabbro and ultramafic cumulates. Due to this higher density, the oceanic crust subducts under the continental crust.