( ( In ( explosive ( volcanic eruptions ) ) ) ( , ( ( ( sudden release ) ( of ( gases ( from magma ) ) ) ) ( ( may ( cause ( ( rapid movements ) ( of ( the ( molten rock ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (JJ explosive) (JJ volcanic) (NNS eruptions))) (, ,) (NP (NP (JJ sudden) (NN release)) (PP (IN of) (NP (NP (NNS gases)) (PP (IN from) (NP (NN magma)))))) (VP (MD may) (VP (VB cause) (NP (NP (JJ rapid) (NNS movements)) (PP (IN of) (NP (DT the) (NN molten) (NN rock)))))) (. .)))
In explosive volcanic eruptions, sudden release of gases from magma may cause rapid movements of the molten rock.
(ROOT (S (NP (NP (DT The) (NN thickness)) (PP (IN of) (NP (NN magma)))) (VP (VBZ determines) (SBAR (IN whether) (S (NP (DT a) (JJ volcanic) (NN eruption)) (VP (MD will) (VP (VB be) (ADJP (JJ explosive))))) (CC or) (RB not))) (. .)))