Some things which seem obvious now could not have been found without maps: that Brazil's bulge fits neatly into West Africa's dent, and so to the theory of plate tectonics, for example.

ECONOMIST: Modern man knows where he stands. His map tells him

By the 1960s, scientists had developed a theory called plate tectonics explaining the locations of volcanoes and other large-scale geologic features.

BBC: The Pacific 'Ring of Fire'

After gorging on bear meat, the expedition's scientists bring back evidence that helps prove the controversial theory of continental drift, which gives rise in due course to the science of plate tectonics, which explains why it was that Krakatoa blew itself up--and will do so again, in eons hence.

FORBES: Don't Go Near The Volcano