( ( Much ( of ( what ( ( ( scientists ( know ( about ( ( Earth 's ) ( internal structure ) ) ) ) ) and ) ( dynamics ( has ( been ( ( ( learned ( by ( studying earthquakes ) ) ) , ) ( since ( ( the waves ) ( that ( are ( generated ( by ( such ( cataclysmic rumblings ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ( ( change ( as ( they ( pass ( through ( ( various layers ) ( of ( ( the ( Earth 's ) ) interior ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (RB Much)) (PP (IN of) (SBAR (WHNP (WP what)) (S (S (NP (NNS scientists)) (VP (VBP know) (PP (IN about) (NP (NP (NNP Earth) (POS 's)) (JJ internal) (NN structure))))) (CC and) (S (NP (NNS dynamics)) (VP (VBZ has) (VP (VBN been) (VP (VBN learned) (PP (IN by) (S (VP (VBG studying) (NP (NNS earthquakes))))) (, ,) (PP (IN since) (NP (NP (DT the) (NNS waves)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (VP (VBN generated) (PP (IN by) (NP (JJ such) (JJ cataclysmic) (NNS rumblings))))))))))))))))) (VP (VBP change) (SBAR (IN as) (S (NP (PRP they)) (VP (VBP pass) (PP (IN through) (NP (NP (JJ various) (NNS layers)) (PP (IN of) (NP (NP (DT the) (NN Earth) (POS 's)) (NN interior))))))))) (. .)))
Much of what scientists know about Earth's internal structure and dynamics has been learned by studying earthquakes, since the waves that are generated by such cataclysmic rumblings change as they pass through various layers of the Earth's interior.
(ROOT (S (NP (NP (NNS Studies)) (PP (IN of) (NP (NN earthquake) (NNS waves)))) (VP (VBP have) (VP (VBN helped) (S (NP (NNS scientists)) (VP (VB determine) (NP (NP (DT the) (NN structure)) (PP (IN of) (NP (NP (NN earth) (POS 's)) (NN interior)))))))) (. .)))
Studies of earthquake waves have helped scientists determine the structure of earth's interior.