( ( ( ( Rock , ) ( ( ( at least ) ( the rock ) ) ( which ( ( makes up ) ( ( the ( earth 's ) ) crust ) ) ) ) ) , ) ( ( ( does n't ) float ) . ) )
(ROOT (S (NP (NP (NNP Rock)) (, ,) (NP (NP (ADVP (IN at) (JJS least)) (DT the) (NN rock)) (SBAR (WHNP (WDT which)) (S (VP (VBZ makes) (PRT (RP up)) (NP (NP (DT the) (NN earth) (POS 's)) (NN crust)))))) (, ,)) (VP (VBZ does) (RB n't) (VP (VB float))) (. .)))
Rock, at least the rock which makes up the earth's crust, doesn't float.
(ROOT (S (NP (NP (DT The) (NN earth) (POS 's)) (NN crust)) (VP (VBZ is) (VP (VBN composed) (PP (IN of) (NP (JJ igneuos) (NN rock))))) (. .)))