( ( ( Convergent margins ) ( involving ( oceanic plates ) ) ) ( ( ( form volcanoes ) ( on ( ( the continent ) ( that ( ( are parallel ) ( to ( the trench ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Convergent) (NNS margins)) (VP (VBG involving) (NP (JJ oceanic) (NNS plates)))) (VP (VBP form) (NP (NNS volcanoes)) (PP (IN on) (NP (NP (DT the) (NN continent)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (RB parallel) (PP (TO to) (NP (DT the) (NN trench))))))))) (. .)))
Convergent margins involving oceanic plates form volcanoes on the continent that are parallel to the trench.
(ROOT (S (PP (IN At) (NP (DT a) (JJ convergent) (NN plate) (NN boundary))) (, ,) (SBAR (WHADVP (WRB when)) (S (NP (CD one) (NN plate)) (VP (VBZ is) (ADJP (JJ oceanic))))) (, ,) (NP (EX there)) (VP (VBP are) (NP (JJ large) (NNS volcanoes))) (. .)))