( ( ( ( ( ( The layers ) ( ( ( are parallel ) ( to ( each other ) ) ) ( because ( they ( were ( ( formed ( by sediments ) ) ( ( ( falling ( to ( ( the bottom ) ( of ( the seas ) ) ) ) ) ( in ( horizontal layers ) ) ) ( -LRB- ( ( see above ) -RRB- ) ) ) ) ) ) ) ) ) , ) but ) ( ( when ( ( the continents ) ( ( crashed together ) ( at ( a ( convergent boundary ) ) ) ) ) ) ( , ( ( ( the ( ( rocks and ) sediment ) ) ( under ( the sea ) ) ) ( were ( ( squished and ) folded ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (NNS layers)) (VP (VBP are) (RB parallel) (PP (TO to) (NP (DT each) (JJ other))) (SBAR (IN because) (S (NP (PRP they)) (VP (VBD were) (VP (VBN formed) (PP (IN by) (NP (NNS sediments))) (S (VP (VBG falling) (PP (TO to) (NP (NP (DT the) (NN bottom)) (PP (IN of) (NP (DT the) (NNS seas))))) (PP (IN in) (NP (JJ horizontal) (NNS layers))) (PRN (-LRB- -LRB-) (S (VP (VB see) (ADVP (RB above)))) (-RRB- -RRB-)))))))))) (, ,) (CC but) (S (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN continents)) (VP (VBD crashed) (ADVP (RB together)) (PP (IN at) (NP (DT a) (JJ convergent) (NN boundary)))))) (, ,) (NP (NP (DT the) (NNS rocks) (CC and) (NN sediment)) (PP (IN under) (NP (DT the) (NN sea)))) (VP (VBD were) (VP (VBN squished) (CC and) (VBN folded)))) (. .)))
The layers are parallel to each other because they were formed by sediments falling to the bottom of the seas in horizontal layers (see above), but when the continents crashed together at a convergent boundary, the rocks and sediment under the sea were squished and folded.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NNS sediments)) (VP (VB settle) (PRT (RP out)) (PP (IN of) (NP (NN water)))))) (, ,) (NP (PRP they)) (VP (VBP form) (NP (JJ horizontal) (NNS layers))) (. .)))
When sediments settle out of water, they form horizontal layers.