( ( The ( outer core ) ) ( ( ( ( composes ( ( 30.8 % ) ( of ( ( Earth 's ) mass ) ) ) ) and ) ( believed ( to ( be ( ( an ( electrically ( conductive layer ) ) ) ( that ( is ( responsible ( for ( ( the ( Earth 's ) ) ( magnetic field ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ outer) (NN core)) (VP (VP (VBZ composes) (NP (NP (CD 30.8) (NN %)) (PP (IN of) (NP (NP (NNP Earth) (POS 's)) (NN mass))))) (CC and) (VP (VBD believed) (S (VP (TO to) (VP (VB be) (NP (NP (DT an) (JJ electrically) (NN conductive) (NN layer)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ responsible) (PP (IN for) (NP (NP (DT the) (NN Earth) (POS 's)) (JJ magnetic) (NN field))))))))))))) (. .)))
The outer core composes 30.8% of Earth's mass and believed to be an electrically conductive layer that is responsible for the Earth's magnetic field.
(ROOT (S (NP (NP (DT The) (JJ outer) (NN core)) (PP (IN of) (NP (DT the) (NN earth)))) (VP (VBZ is) (ADJP (JJ molten))) (. .)))