( However ( , ( ( many ( of ( ( the ( ocean 's ) ) ( volcanic ( ( islands and ) seamounts ) ) ) ) ) ( ( are ( found ( in ( what ( are ( ( ( called ( island arcs ) ) , ) ( ( ( ( bending ( chains ( of ( islands ( rising ( from ( the ( sea floor ) ) ) ) ) ) ) ) , ) usually ) ( paralleling ( ( the ( concave edges ) ) ( of ( an ( oceanic trench ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB However)) (, ,) (NP (NP (JJ many)) (PP (IN of) (NP (NP (DT the) (NN ocean) (POS 's)) (JJ volcanic) (NNS islands) (CC and) (NNS seamounts)))) (VP (VBP are) (VP (VBN found) (PP (IN in) (SBAR (WHNP (WP what)) (S (VP (VBP are) (VP (VBN called) (NP (NN island) (NNS arcs)) (, ,) (S (VP (VP (VBG bending) (NP (NP (NNS chains)) (PP (IN of) (NP (NP (NNS islands)) (VP (VBG rising) (PP (IN from) (NP (DT the) (NN sea) (NN floor)))))))) (, ,) (ADVP (RB usually)) (VP (VBG paralleling) (NP (NP (DT the) (JJ concave) (NNS edges)) (PP (IN of) (NP (DT an) (JJ oceanic) (NN trench)))))))))))))) (. .)))
However, many of the ocean's volcanic islands and seamounts are found in what are called island arcs, bending chains of islands rising from the sea floor, usually paralleling the concave edges of an oceanic trench.
(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)))) (. .)))