( ( ( Rift basins ) ( that ( ( ( form along ) ( ( the margins ) ( of continents ) ) ) ( during ( ( the ( tectonic opening ) ) ( of ( an ( ocean basin ) ) ) ) ) ) ) ) ( ( may ( ( contain ( ( ( unusually rich ) concentrations ) ( of oil ) ) ) ( if ( ( ( the timing ) ( of ( geologic events ) ) ) ( ( ( ( was appropriate ) , ) or ) ( may ( ( contain ( ( virtually no ) ( energy resources ) ) ) ( if ( ( the timing ) ( was inappropriate ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Rift) (NNS basins)) (SBAR (WHNP (WDT that)) (S (VP (VBP form) (PRT (RP along)) (NP (NP (DT the) (NNS margins)) (PP (IN of) (NP (NNP continents)))) (PP (IN during) (NP (NP (DT the) (JJ tectonic) (NN opening)) (PP (IN of) (NP (DT an) (NN ocean) (NN basin))))))))) (VP (MD may) (VP (VB contain) (NP (NP (ADJP (RB unusually) (JJ rich)) (NNS concentrations)) (PP (IN of) (NP (NN oil)))) (SBAR (IN if) (S (NP (NP (DT the) (NN timing)) (PP (IN of) (NP (JJ geologic) (NNS events)))) (VP (VP (VBD was) (ADJP (JJ appropriate))) (, ,) (CC or) (VP (MD may) (VP (VB contain) (NP (ADJP (RB virtually) (DT no)) (NN energy) (NNS resources)) (SBAR (IN if) (S (NP (DT the) (NN timing)) (VP (VBD was) (ADJP (JJ inappropriate)))))))))))) (. .)))
Rift basins that form along the margins of continents during the tectonic opening of an ocean basin may contain unusually rich concentrations of oil if the timing of geologic events was appropriate, or may contain virtually no energy resources if the timing was inappropriate.
(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.