( ( ( ( ocean basins ) , ) and ) ( continents ( ( ( ( ( takes tens ) ( to ( hundreds ( of ( millions ( of years ) ) ) ) ) ) , ) and ) ( ( large ( time units ) ) thus ) ) ) )
(ROOT (S (S (NP (NN ocean)) (VP (VBZ basins))) (, ,) (CC and) (S (NP (NNP continents)) (VP (VP (VBZ takes) (NP (NNS tens)) (PP (TO to) (NP (NP (NNS hundreds)) (PP (IN of) (NP (NP (NNS millions)) (PP (IN of) (NP (NNS years)))))))) (, ,) (CC and) (VP (NP (JJ large) (NN time) (NNS units)) (ADVP (RB thus)))))))
ocean basins, and continents takes tens to hundreds of millions of years, and large time units thus
(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.