( Stratigraphy ( ( is ( ( the study ) ( of ( ( ( how ( ( ( rock layers ) ( in ( ( the ( earth 's ) ) crust ) ) ) ( were formed ) ) ) and ) ( how ( they ( relate ( to ( each other ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Stratigraphy)) (VP (VBZ is) (NP (NP (DT the) (NN study)) (PP (IN of) (SBAR (SBAR (WHADVP (WRB how)) (S (NP (NP (NN rock) (NNS layers)) (PP (IN in) (NP (NP (DT the) (NN earth) (POS 's)) (NN crust)))) (VP (VBD were) (VP (VBN formed))))) (CC and) (SBAR (WHADVP (WRB how)) (S (NP (PRP they)) (VP (VBP relate) (PP (TO to) (NP (DT each) (JJ other)))))))))) (. .)))
Stratigraphy is the study of how rock layers in the earth's crust were formed and how they relate to each other.
(ROOT (S (NP (PRP We)) (VP (VBP call) (NP (NP (DT the) (NN study)) (PP (IN of) (NP (NN rock) (NNS layers)))) (ADVP (RB stratigraphy))) (. .)))