( Stratigraphy ( ( is ( ( a branch ) ( of ( ( geology ( which ( studies ( rock formations ) ) ) ) ( -LRB- ( layers -RRB- ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Stratigraphy)) (VP (VBZ is) (NP (NP (DT a) (NN branch)) (PP (IN of) (NP (NP (NN geology)) (SBAR (WHNP (WDT which)) (S (VP (VBZ studies) (NP (NN rock) (NNS formations))))) (PRN (-LRB- -LRB-) (NP (NNP layers)) (-RRB- -RRB-)))))) (. .)))
Stratigraphy is a branch of geology which studies rock formations (layers).
(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))) (. .)))