( ( The crust ) ( ( can ( be ( ( ( ( ( divided ( into ( ( ( ( ocean basins ) , ) ( underlain ( by ( ( a ( thin layer ) ) ( of ( dense ( , ( basaltic rock ) ) ) ) ) ) ) ) , ) ) ) and ) continents ) , ) ( formed ( of ( ( a ( ( ( ( much thicker ) but ) less-dense ) layer ) ) ( of ( granitic rocks ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN crust)) (VP (MD can) (VP (VB be) (VP (VP (VBN divided) (PP (IN into) (NP (NP (NN ocean) (NNS basins)) (, ,) (VP (VBN underlain) (PP (IN by) (NP (NP (DT a) (JJ thin) (NN layer)) (PP (IN of) (NP (JJ dense) (, ,) (JJ basaltic) (NN rock)))))) (, ,)))) (CC and) (VP (JJ continents)) (, ,) (VP (VBN formed) (PP (IN of) (NP (NP (DT a) (ADJP (ADJP (RB much) (JJ thicker)) (CC but) (ADJP (JJ less-dense))) (NN layer)) (PP (IN of) (NP (JJ granitic) (NNS rocks))))))))) (. .)))
The crust can be divided into ocean basins, underlain by a thin layer of dense, basaltic rock, and continents, formed of a much thicker but less-dense layer of granitic rocks.
(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.