( They ( ( may ( ( determine ( the ( rock formations ) ) ) ( on ( ( the ( Earth 's ) ) crust ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (MD may) (VP (VB determine) (NP (DT the) (NN rock) (NNS formations)) (PP (IN on) (NP (NP (DT the) (NN Earth) (POS 's)) (NN crust))))) (. .)))
They may determine the rock formations on the Earth's crust.
(ROOT (S (NP (NP (DT The) (NN earth) (POS 's)) (NN crust)) (VP (VBZ is) (VP (VBN composed) (PP (IN of) (NP (JJ igneuos) (NN rock))))) (. .)))