( ( ( ( ( ( The Law ) ( of Superposition ) ) , ) ( which ( states ( that ( ( in ( ( an ( ( undisturbed horizontal ) sequence ) ) ( of rocks ) ) ) ( , ( ( the ( oldest ( rock layers ) ) ) ( will ( ( ( be ( on ( the bottom ) ) ) , ) ( with ( ( successively ( younger rocks ) ) ( on ( top ( of these ) ) ) ) ) ) ) ) ) ) ) ) ) ) , ) ( ( ( helps ( geologists ( correlate ( rock layers ) ) ) ) ( around ( the world ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN Law)) (PP (IN of) (NP (NNP Superposition))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ states) (SBAR (IN that) (S (PP (IN in) (NP (NP (DT an) (ADJP (JJ undisturbed) (JJ horizontal)) (NN sequence)) (PP (IN of) (NP (NNS rocks))))) (, ,) (NP (DT the) (JJS oldest) (NN rock) (NNS layers)) (VP (MD will) (VP (VB be) (PP (IN on) (NP (DT the) (NN bottom))) (, ,) (PP (IN with) (S (VP (VBG successively) (NP (JJR younger) (NNS rocks)) (PP (IN on) (NP (NP (NN top)) (PP (IN of) (NP (DT these))))))))))))))) (, ,)) (VP (VBZ helps) (NP (JJ geologists) (JJ correlate) (NN rock) (NNS layers)) (PP (IN around) (NP (DT the) (NN world)))) (. .)))
The Law of Superposition, which states that in an undisturbed horizontal sequence of rocks, the oldest rock layers will be on the bottom, with successively younger rocks on top of these, helps geologists correlate rock layers around the world.
(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.