( ( Calderas ( and ( pit craters ) ) ) ( ( ( form ( above ( a ( collapsed ( ( , ( or ( partially ( collapsed , ) ) ) ) ( magma chamber ) ) ) ) ) ) ( after ( a ( large eruption ) ) ) ) . ) )
(ROOT (S (NP (NNS Calderas) (CC and) (NN pit) (NNS craters)) (VP (VBP form) (PP (IN above) (NP (DT a) (JJ collapsed) (PRN (, ,) (CC or) (ADVP (RB partially)) (NP (JJ collapsed)) (, ,)) (JJ magma) (NN chamber))) (PP (IN after) (NP (DT a) (JJ large) (NN eruption)))) (. .)))
Calderas and pit craters form above a collapsed, or partially collapsed, magma chamber after a large eruption.
(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)))) (. .)))