( ( ( A model ) ( for ( a ( subduction zone ) ) ) ) ( ( ( begins ( to ( ( ( ( take shape ) then ) , ) ( of ( ( the ( water-saturated ( oceanic plate ) ) ) ( ( ( ( ( ( subducting and ) ( partially melting ) ) , ) ( forming ( on ( the surface ) ) ) ) , ) ( ( a chain ) ( of ( composite volcanoes ) ) ) ) ) ) ) ) ) ( within ( ( an ( andesitic ( magmatic arc ) ) ) ( which ( is ( convex oceanward ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN model)) (PP (IN for) (NP (DT a) (NN subduction) (NN zone)))) (VP (VBZ begins) (S (VP (TO to) (VP (VB take) (NP (NN shape)) (ADVP (RB then)) (, ,) (PP (IN of) (S (NP (DT the) (JJ water-saturated) (JJ oceanic) (NN plate)) (VP (VP (VBG subducting)) (CC and) (VP (ADVP (RB partially)) (VBG melting)) (, ,) (VP (VBG forming) (PP (IN on) (NP (DT the) (NN surface)))) (, ,) (NP (NP (DT a) (NN chain)) (PP (IN of) (NP (JJ composite) (NNS volcanoes)))))))))) (PP (IN within) (NP (NP (DT an) (JJ andesitic) (JJ magmatic) (NN arc)) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADJP (RB convex) (JJ oceanward)))))))) (. .)))
A model for a subduction zone begins to take shape then, of the water-saturated oceanic plate subducting and partially melting, forming on the surface, a chain of composite volcanoes within an andesitic magmatic arc which is convex oceanward.
(ROOT (S (NP (DT A) (NN volcano) (NN chain)) (VP (VBZ is) (VP (VBN formed) (PP (IN by) (NP (NP (NN subduction)) (PP (IN of) (NP (JJ oceanic) (NN crust))))) (PP (IN beneath) (NP (DT a) (ADJP (JJ continental) (CC or) (JJ oceanic)) (NN plate))))) (. .)))