( ( Because ( of ( its ( numerous ( gas bubbles ) ) ) ) ) ( , ( pumice ( commonly ( ( floats ( on water ) ) . ) ) ) ) )
(ROOT (S (PP (IN Because) (PP (IN of) (NP (PRP$ its) (JJ numerous) (NN gas) (NNS bubbles)))) (, ,) (NP (NN pumice)) (ADVP (RB commonly)) (VP (VBZ floats) (PP (IN on) (NP (NN water)))) (. .)))
Because of its numerous gas bubbles, pumice commonly floats on water.
(ROOT (S (NP (NNP Gas) (NN bubble) (NNS holes)) (VP (VBZ helps) (NP (NP (JJ pumice) (NN float)) (PP (IN in) (NP (NN water))))) (. .)))