( ( ( The principle ) ( of superposition ) ) ( ( states ( that ( ( in ( ( an ( undisturbed stack ) ) ( of ( sedimentary strata ) ) ) ) ( ( the ( oldest layer ) ) ( ( is ( at ( ( ( the base ) and ) ( the youngest ) ) ) ) ( at ( the top ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN principle)) (PP (IN of) (NP (NN superposition)))) (VP (VBZ states) (SBAR (IN that) (S (PP (IN in) (NP (NP (DT an) (ADJP (JJ undisturbed)) (NN stack)) (PP (IN of) (NP (JJ sedimentary) (NN strata))))) (NP (DT the) (JJS oldest) (NN layer)) (VP (VBZ is) (PP (IN at) (NP (NP (DT the) (NN base)) (CC and) (NP (DT the) (JJS youngest)))) (PP (IN at) (NP (DT the) (NN top))))))) (. .)))
The principle of superposition states that in an undisturbed stack of sedimentary strata the oldest layer is at the base and the youngest at the top.
(ROOT (S (S (NP (NP (DT The) (NN law)) (PP (IN of) (NP (NN superposition)))) (VP (VBZ is) (VP (RBS best) (VBN described) (PP (IN by))))) (: :) (S (PP (IN in) (NP (NP (JJ undisturbed) (NNS layers)) (PP (IN of) (NP (JJ sedimentary) (NN rock))))) (, ,) (NP (DT the) (JJS lowest) (NNS layers)) (VP (VBP contain) (NP (DT the) (JJR older) (NNS rocks)))) (. .)))
The law of superposition is best described by: in undisturbed layers of sedimentary rock, the lowest layers contain the older rocks.