( Calderas ( ( are ( ( massive craters ) ( ( up ( to ( ( ( several hundred ) ( square miles ) ) ( in area ) ) ) ) ( formed ( when ( ( explosive eruptions ) ( ( ( ( emptied ( magma chambers ) ) ( beneath ( ( the ( earth 's ) ) crust ) ) ) , ) ( ( causing ( the surface ) ) ( to collapse ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Calderas)) (VP (VBP are) (NP (NP (JJ massive) (NNS craters)) (VP (ADVP (RB up) (PP (TO to) (NP (NP (QP (JJ several) (CD hundred)) (JJ square) (NNS miles)) (PP (IN in) (NP (NN area)))))) (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (JJ explosive) (NNS eruptions)) (VP (VBN emptied) (NP (NN magma) (NNS chambers)) (PP (IN beneath) (NP (NP (DT the) (NN earth) (POS 's)) (NN crust))) (, ,) (S (VP (VBG causing) (NP (DT the) (NN surface)) (PP (TO to) (NP (NN collapse))))))))))) (. .)))
Calderas are massive craters up to several hundred square miles in area formed when explosive eruptions emptied magma chambers beneath the earth's crust, causing the surface to collapse.
(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)))) (. .)))