( ( ( The ( D' ' ) ) layer ) ( ( ( ( is ( ( ( about 300 ) kilometers ) thick ) ) and ) ( overlies ( ( the ( liquid metal ) ) ( of ( the ( outer core ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNP D') (POS ')) (NN layer)) (VP (VP (VBZ is) (ADJP (NP (QP (RB about) (CD 300)) (NNS kilometers)) (JJ thick))) (CC and) (VP (VBZ overlies) (NP (NP (DT the) (JJ liquid) (NN metal)) (PP (IN of) (NP (DT the) (JJ outer) (NN core)))))) (. .)))
The D'' layer is about 300 kilometers thick and overlies the liquid metal of the outer core.
(ROOT (S (NP (DT The) (JJ outer) (NN core)) (VP (VBZ is) (VP (VBN made) (PP (IN of) (NP (JJ liquid) (NN metal))))) (. .)))