( ( ( ( ( ( The ( Montrose spit ) ) ( , ( ( unlike ( an ( offshore breakwater ) ) ) ( , ( allows ( ( these waves ) ( to ( crash ( against ( the shore ) ) ) ) ) ) ) ) ) ) , ) but ) ( ( ( the energy ) ( of ( the waves ) ) ) ( ( ( ( stays ( on ( the beach ) ) ) , ) and ) ( ( keeps ( the sand ) ) ( on ( ( the beach ) ( from ( migrating southward ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (NNP Montrose) (NN spit)) (, ,) (PP (IN unlike) (NP (DT an) (JJ offshore) (NN breakwater))) (, ,) (VP (VBZ allows) (S (NP (DT these) (NNS waves)) (VP (TO to) (VP (VB crash) (PP (IN against) (NP (DT the) (NN shore)))))))) (, ,) (CC but) (S (NP (NP (DT the) (NN energy)) (PP (IN of) (NP (DT the) (NNS waves)))) (VP (VP (VBZ stays) (PP (IN on) (NP (DT the) (NN beach)))) (, ,) (CC and) (VP (VBZ keeps) (NP (DT the) (NN sand)) (PP (IN on) (NP (NP (DT the) (NN beach)) (PP (IN from) (NP (JJ migrating) (NN southward)))))))) (. .)))
The Montrose spit, unlike an offshore breakwater, allows these waves to crash against the shore, but the energy of the waves stays on the beach, and keeps the sand on the beach from migrating southward.
(ROOT (S (NP (NNP Low) (NN energy)) (VP (VBZ causes) (S (NP (NNS waves)) (VP (TO to) (VP (VB bring) (NP (NN sand)) (PRT (RP up)) (PP (IN onto) (NP (NP (DT the) (NN beach)) (PP (IN during) (NP (NNS summers))))))))) (. .)))