( ( ( ( Atolls ( ( are also ) ( created ( when ( ( water levels ) ( rise ( to ( cover ( an island ) ) ) ) ) ) ) ) ) and ) ( ( the ( surrounding reef ) ) ( grows ( to ( ( keep up ) ( with ( ( the surface ) ( of ( the water ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNS Atolls)) (VP (VBP are) (ADVP (RB also)) (VP (VBN created) (SBAR (WHADVP (WRB when)) (S (NP (NN water) (NNS levels)) (VP (VBP rise) (S (VP (TO to) (VP (VB cover) (NP (DT an) (NN island))))))))))) (CC and) (S (NP (DT the) (VBG surrounding) (NN reef)) (VP (VBZ grows) (S (VP (TO to) (VP (VB keep) (PRT (RP up)) (PP (IN with) (NP (NP (DT the) (NN surface)) (PP (IN of) (NP (DT the) (NN water)))))))))) (. .)))
Atolls are also created when water levels rise to cover an island and the surrounding reef grows to keep up with the surface of the water.
(ROOT (S (NP (NP (NNS Seamounts)) (SBAR (WHNP (WDT that)) (S (VP (VBP rise) (PP (IN above) (NP (DT the) (NN water) (NN surface))))))) (VP (VBP are) (VP (VBN called) (NP (NNS islands)))) (. .)))