( ( ( ( ( ( Magma ( -LRB- ( ( liquid rock ) -RRB- ) ) ) ( ( forced ( its way ) ) ( through ( ( the ( weaker parts ) ) ( of ( ( ( the ( earth 's ) ) crust ) ( -LRB- ( ( volcanic eruptions ) -RRB- ) ) ) ) ) ) ) ) , ) and ) ( ( when ( ( ( the magma ) ( from ( many eruptions ) ) ) cooled ) ) ( it ( gradually ( formed ( ( the islands ) ( of Japan ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNP Magma)) (PRN (-LRB- -LRB-) (ADJP (JJ liquid) (NN rock)) (-RRB- -RRB-))) (VP (VBD forced) (NP (PRP$ its) (NN way)) (PP (IN through) (NP (NP (DT the) (JJR weaker) (NNS parts)) (PP (IN of) (NP (NP (NP (DT the) (NN earth) (POS 's)) (NN crust)) (PRN (-LRB- -LRB-) (NP (JJ volcanic) (NNS eruptions)) (-RRB- -RRB-)))))))) (, ,) (CC and) (S (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN magma)) (PP (IN from) (NP (JJ many) (NNS eruptions)))) (VP (VBD cooled)))) (NP (PRP it)) (ADVP (RB gradually)) (VP (VBD formed) (NP (NP (DT the) (NNS islands)) (PP (IN of) (NP (NNP Japan)))))) (. .)))
Magma (liquid rock) forced its way through the weaker parts of the earth's crust (volcanic eruptions), and when the magma from many eruptions cooled it gradually formed the islands of Japan.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN magma)) (VP (VBZ reaches) (NP (DT the) (NN surface)) (PP (IN through) (NP (NP (NNS cracks)) (PP (IN in) (NP (NP (DT the) (NN earth) (POS 's)) (NN crust)))))))) (, ,) (NP (DT a) (JJ volcanic) (NN eruption)) (VP (VBZ occurs)) (. .)))