( Volcanoes ( ( occur ( where ( plates ( are ( ( ( subducted ( -LRB- ( ( ( an ( ocean plate ) ) ( pushed ( under ( a ( ( ( continental or ) another ) ( oceanic plate ) ) ) ) ) ) -RRB- ) ) ) or ) ( move ( apart ( -LRB- ( ( ( mid-ocean ( ( ridges or ) rifts ) ) ( in continents ) ) -RRB- ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Volcanoes)) (VP (VBP occur) (SBAR (WHADVP (WRB where)) (S (NP (NNS plates)) (VP (VBP are) (VP (VP (VBN subducted)) (PRN (-LRB- -LRB-) (S (NP (DT an) (NN ocean) (NN plate)) (VP (VBD pushed) (PP (IN under) (NP (DT a) (ADJP (JJ continental) (CC or) (DT another)) (JJ oceanic) (NN plate))))) (-RRB- -RRB-)) (CC or) (VP (VBP move) (ADVP (ADVP (RB apart)) (PRN (-LRB- -LRB-) (NP (NP (JJ mid-ocean) (NNS ridges) (CC or) (NNS rifts)) (PP (IN in) (NP (NNP continents)))) (-RRB- -RRB-))))))))) (. .)))
Volcanoes occur where plates are subducted (an ocean plate pushed under a continental or another oceanic plate) or move apart (mid-ocean ridges or rifts in continents).
(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))))) (. .)))