( ( When ( ( ( ( oceanic crust ) and ) ( continental crust ) ) collide ) ) ( , ( ( continental crust ) ( , ( ( being ( less dense ) ) ( ( ( will usually ) ( ( ride up ) ( over ( the ( oceanic crust ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (JJ oceanic) (NN crust)) (CC and) (NP (JJ continental) (NN crust))) (VP (VBP collide)))) (, ,) (NP (JJ continental) (NN crust)) (, ,) (S (VP (VBG being) (ADJP (RBR less) (JJ dense)))) (VP (MD will) (ADVP (RB usually)) (VP (VB ride) (PRT (RP up)) (PP (IN over) (NP (DT the) (JJ oceanic) (NN crust))))) (. .)))
When oceanic crust and continental crust collide , continental crust, being less dense will usually ride up over the oceanic crust.
(ROOT (S (NP (NNP Gabbro)) (VP (VBZ is) (NP (NP (DT a) (JJ dark) (JJ dense) (NN rock)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB be) (VP (VBN found) (PP (IN in) (NP (DT the) (JJ oceanic) (NN crust)))))))))) (. .)))
Gabbro is a dark dense rock that can be found in the oceanic crust.