The effect of the word vastly on the author´s purpose is making the readers understand that such an extent of land and opportunities should not be ignored. The author emphasizes the meaning of the adjective by making use of an adverb that refers to many different things. The great proportion of land, all its untouched resources, and the enormous gain there would be if properly used. In short, the author emphasizes that Antarctica is not being explored nearly enough as it could be.
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