( ( In ( a geyser ) ) ( , ( ( steam bubbles ) ( ( ( ( ( flow upward ) ( from ( the ( heated source ) ) ) ) and ) ( expands ( as ( it ( ( rises , ) ( ( ( blocking ( the ( plumbing system ) ) ) , ) ( ( keeping ( the water ) ) ( from ( reaching ( the surface ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT a) (NN geyser))) (, ,) (NP (NN steam) (NNS bubbles)) (VP (VP (VBP flow) (ADVP (RB upward)) (PP (IN from) (NP (DT the) (VBN heated) (NN source)))) (CC and) (VP (VBZ expands) (SBAR (IN as) (S (NP (PRP it)) (VP (VBZ rises) (, ,) (S (VP (VP (VBG blocking) (NP (DT the) (NN plumbing) (NN system))) (, ,) (VP (VBG keeping) (NP (DT the) (NN water)) (PP (IN from) (S (VP (VBG reaching) (NP (DT the) (NN surface))))))))))))) (. .)))
In a geyser, steam bubbles flow upward from the heated source and expands as it rises, blocking the plumbing system, keeping the water from reaching the surface.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN water)) (VP (VP (VBZ is) (VP (VP (VBN heated) (PP (IN by) (NP (NN magma)))) (CC and) (VP (VBZ makes) (NP (PRP$ its) (NN way)) (PP (TO to) (NP (DT the) (NN surface)))))) (CC and) (VP (VBZ creates))))) (NP (DT a) (-LRB- -LRB-) (NN n) (-RRB- -RRB-)) (VP (VBP geyser)) (. .)))