21.   The west coast of South America provides an example of oceanic lithosphere subduction beneath continental lithosphere.

22.   Where oceanic lithosphere is subducted beneath another oceanic part of a plate the associated volcanic activity and produce an intra-oceanic island arc.

23.   Subduction of oceanic lithosphere beneath a plate carrying continental crust gives rise to a continental-margin orogen.

24.   At a subduction zone the downgoing oceanic lithosphere finds its topographic expression in the trench formed on the frontal side of the island arc.

25.   As with an intra-oceanic island arc the oceanward side of a continental-margin orogen is marked by an oceanic trench associated with the downgoing oceanic lithosphere.

26.   The sequence of continental-margin orogen development begins with the subduction of oceanic lithosphere at, or close to, a continental margin.

27.   Such mountain belts develop when the oceanic lithosphere originally lying between two continents is eventually consumed.

28.   A retroarc foreland basin occurs on the overriding plate behind the volcanic arc previously developed in association with the earlier subduction of oceanic lithosphere.

29.   Here oceanic lithosphere of the Indian Plate is being subducted beneath oceanic and continental lithosphere of the Eurasian Plate.

30.   The largest examples are to be found on oceanic lithosphere marking the site of hot spots.