( ( ( A century ) ago ) ( , ( Antarctica ( ( was ( ( the ( Earth 's ) ) ( only ( unexplored continent ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (NP (DT A) (NN century)) (RB ago)) (, ,) (NP (NNP Antarctica)) (VP (VBD was) (NP (NP (DT the) (NN Earth) (POS 's)) (JJ only) (JJ unexplored) (NN continent))) (. .)))
A century ago, Antarctica was the Earth's only unexplored continent.
(ROOT (S (NP (NNP Antarctica)) (VP (VBZ is) (NP (NP (DT the) (JJ only) (NN continent)) (PP (IN without) (NP (NNS amphibians))))) (. .)))