( ( As ( ( the eruptions ) ( partly ( empty ( ( the chamber ) ( of ( its magma ) ) ) ) ) ) ) ( , ( ( ( the roof ) ( of ( the ( magma chamber ) ) ) ) ( ( ( collapses ( along ( the ( same ( ring fractures ) ) ) ) ) ( to ( produce ( a ( large caldera ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NNS eruptions)) (ADVP (RB partly)) (VP (VBP empty) (NP (NP (DT the) (NN chamber)) (PP (IN of) (NP (PRP$ its) (NN magma))))))) (, ,) (NP (NP (DT the) (NN roof)) (PP (IN of) (NP (DT the) (NN magma) (NN chamber)))) (VP (VBZ collapses) (PP (IN along) (NP (DT the) (JJ same) (NN ring) (NNS fractures))) (S (VP (TO to) (VP (VB produce) (NP (DT a) (JJ large) (NN caldera)))))) (. .)))
As the eruptions partly empty the chamber of its  magma, the roof of the magma chamber collapses along the same ring fractures to  produce a large caldera .
(ROOT (S (PP (IN After) (NP (DT a) (JJ massive) (NN eruption))) (, ,) (NP (NP (DT a) (NN mountain)) (VP (VBG collapsing) (PP (IN above) (NP (DT an) (JJ empty) (NN chamber))))) (VP (MD will) (VP (VB create) (NP (DT a) (NN caldera)))) (. .)))