( island ( ( arc ( ( ( An ( arc-shaped chain ) ) ( of ( volcanic islands ) ) ) ( produced ( where ( ( an ( oceanic plate ) ) ( is ( ( sinking ( -LRB- ( subducting -RRB- ) ) ) ( beneath another ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN island)) (VP (VBP arc) (SBAR (S (NP (NP (DT An) (JJ arc-shaped) (NN chain)) (PP (IN of) (NP (JJ volcanic) (NNS islands)))) (VP (VBD produced) (SBAR (WHADVP (WRB where)) (S (NP (DT an) (JJ oceanic) (NN plate)) (VP (VBZ is) (NP (NP (VBG sinking)) (PRN (-LRB- -LRB-) (NP (NN subducting)) (-RRB- -RRB-)) (PP (IN beneath) (NP (DT another))))))))))) (. .)))
island arc An arc-shaped chain of volcanic islands produced where an oceanic plate is sinking ( subducting ) beneath another.
(ROOT (S (NP (DT A) (JJ volcanic) (NN arc)) (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (VBG subducting) (NN plate)) (VP (VBZ flows) (PP (IN under) (NP (DT another) (JJ tectonic) (NN plate)))))))) (. .)))