(S (S (PP (NP (PP (NP (S-REL (PP (NP (PP (BASENP (NN 火山)) (IN の)) (NN 上)) (IN に)) (S-NSBJ (VP (VBV 生じ) (VP (MD た))))) (BASENP (NN 灰) (NN 雲))) (IN の)) (NN 中)) (IN で)) (S (PP-SBJ (BASENP (NN 稲妻)) (IN が)) (VP (VP (VP (NN 観測) (VBO さ)) (VP (VBV れ))) (VP (MD た))))) (PERIOD 。))
火山 の 上 に 生じ た 灰 雲 の 中 で 稲妻 が 観測 さ れ た 。
Lightning was observed within an ash cloud that formed over the volcano .