( ( ( ( ( ( ( Such measurements ) ( on ( rocks ( of ( different ages ) ) ) ) ) ( provide ( ( a means ) ( of ( tracing ( ( ( ( the movements ) ( of ( ( continents and ) islands ) ) ) and ) ( ( ocean basins ) ( over ( geologic time ) ) ) ) ) ) ) ) ) , ) and ) ( ( ( the record ) ( of ( these movements ) ) ) ( ( shows ( ( great changes ) ( in ( ( the ( Earth 's ) ) geography ) ) ) ) ( during ( its ( long history ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (JJ Such) (NNS measurements)) (PP (IN on) (NP (NP (NNS rocks)) (PP (IN of) (NP (JJ different) (NNS ages)))))) (VP (VBP provide) (NP (NP (DT a) (NN means)) (PP (IN of) (S (VP (VBG tracing) (NP (NP (NP (DT the) (NNS movements)) (PP (IN of) (NP (NNS continents) (CC and) (NNS islands)))) (CC and) (NP (NP (NN ocean) (NNS basins)) (PP (IN over) (NP (JJ geologic) (NN time))))))))))) (, ,) (CC and) (S (NP (NP (DT the) (NN record)) (PP (IN of) (NP (DT these) (NNS movements)))) (VP (VBZ shows) (NP (NP (JJ great) (NNS changes)) (PP (IN in) (NP (NP (DT the) (NN Earth) (POS 's)) (NN geography)))) (PP (IN during) (NP (PRP$ its) (JJ long) (NN history))))) (. .)))
Such measurements on rocks of different ages provide a means of tracing the movements of continents and islands and ocean basins over geologic time, and the record of these movements shows great changes in the Earth's geography during its long history.
(ROOT (S (S (NP (DT This) (NN process)) (ADVP (RB usually)) (VP (VBZ takes) (NP (NP (DT the) (JJS longest) (NN amount)) (PP (IN of) (NP (NN time)))))) (: :) (S (NP (DT an) (NN ocean) (NN basin)) (VP (VBZ forms) (PP (IN between) (NP (CD two) (NNS continents))))) (. .)))
This process usually takes the longest amount of time: an ocean basin forms between two continents.