( ( ( ( ( ( The production ) ( of ( ( large quantities ) ( of magma ) ) ) ) , ) ( variously ( attributed ( ( ( to ( mantle plumes ) ) or ) ( to ( extensional tectonics ) ) ) ) ) ) , ) ( further ( ( ( ( ( pushed ( sea levels ) ) up ) , ) ( so ( that ( ( ( large areas ) ( of ( the ( continental crust ) ) ) ) ( were ( covered ( with ( shallow seas ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (NP (NP (DT The) (NN production)) (PP (IN of) (NP (NP (JJ large) (NNS quantities)) (PP (IN of) (NP (NN magma))))) (, ,) (VP (ADVP (RB variously)) (VBN attributed) (PP (PP (TO to) (NP (JJ mantle) (NNS plumes))) (CC or) (PP (TO to) (NP (JJ extensional) (NNS tectonics))))) (, ,)) (ADVP (RB further)) (VP (VBD pushed) (NP (NN sea) (NNS levels)) (PRT (RP up)) (, ,) (SBAR (RB so) (IN that) (S (NP (NP (JJ large) (NNS areas)) (PP (IN of) (NP (DT the) (JJ continental) (NN crust)))) (VP (VBD were) (VP (VBN covered) (PP (IN with) (NP (JJ shallow) (NNS seas)))))))) (. .)))
The production of large quantities of magma, variously attributed to mantle plumes or to extensional tectonics, further pushed sea levels up, so that large areas of the continental crust were covered with shallow seas.
(ROOT (S (NP (NNP Magma)) (VP (VBZ comes) (PP (IN toward) (NP (NP (NN earth) (POS 's)) (NN crust))) (PP (IN through) (NP (JJ mantle) (NNS plumes)))) (. .)))