( ( ( ( ( A maar ) ( is ( ( a ( low ( relief ( volcanic crater ) ) ) ) ( produced ( by ( ( the interaction ) ( of ( rising ( magma ( and ( ground water ) ) ) ) ) ) ) ) ) ) ) and ) ( ( the product ) ( is ( shallow ( explosive eruptions ) ) ) ) ) . )
(ROOT (S (S (NP (DT A) (NN maar)) (VP (VBZ is) (NP (NP (DT a) (JJ low) (NN relief) (NN volcanic) (NN crater)) (VP (VBN produced) (PP (IN by) (NP (NP (DT the) (NN interaction)) (PP (IN of) (NP (VBG rising) (NN magma) (CC and) (NN ground) (NN water))))))))) (CC and) (S (NP (DT the) (NN product)) (VP (VBZ is) (NP (JJ shallow) (JJ explosive) (NNS eruptions)))) (. .)))
A maar is a low relief volcanic crater produced by the interaction of rising magma and ground water and the product is shallow explosive eruptions.
(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))) (. .)))